What is the correct value of Neuronal Resting Potential - is it -65mV or -70mV?

Some books show the resting potential of neurons as -65mV, such as Neuroscience: Exploring the Brain, Fourth Edition (2016, published by Wolters Kluwer).

However, a majority of internet sites, including Wikipedia, show the resting potential as -70mV.

Which one of these is the correct value, and why is there this small difference?

Neither is incorrect. Neuronal resting potential is a function of the internal and external concentrations of ions and the conductance of the membrane to those ions via ion channels. Different neurons exhibit a range of resting potentials.

You can calculate the resting potential for a given cell using the Goldman Equation.

Crossing the Chloride Channel: The Current and Potential Therapeutic Value of the Neuronal K + -Cl - Cotransporter KCC2

Chloride (Cl - ) homeostasis is an essential process involved in neuronal signalling and cell survival. Inadequate regulation of intracellular Cl - interferes with synaptic signalling and is implicated in several neurological diseases. The main inhibitory neurotransmitter of the central nervous system is γ-aminobutyric acid (GABA). GABA hyperpolarises the membrane potential by activating Cl - permeable

. This process is reliant on Cl - extruder K + -Cl - cotransporter 2 (KCC2), which generates the neuron’s inward, hyperpolarising Cl - gradient. KCC2 is encoded by the fifth member of the solute carrier 12 family (SLC12A5) and has remained a poorly understood component in the development and severity of many neurological diseases for many years. Recent advancements in next-generation sequencing and specific gene targeting, however, have indicated that loss of KCC2 activity is involved in a number of diseases including epilepsy and schizophrenia. It has also been implicated in neuropathic pain following spinal cord injury. Any variant of SLC12A5 that negatively regulates the transporter’s expression may, therefore, be implicated in neurological disease. A recent whole exome study has discovered several causative mutations in patients with epilepsy. Here, we discuss the implications of KCC2 in neurological disease and consider the evolving evidence for KCC2’s potential as a therapeutic target.

1. Introduction

Chloride (Cl - ) is an abundant anion involved in a variety of physiological processes including gene regulation [1, 2], pH maintenance [3], and control of cell volume [4]. Primarily important in the neuron, Cl - plays a crucial role in signalling within the central nervous system (CNS). Healthy brain function requires the correct balance of neuronal excitation and inhibition to determine the firing of action potentials. Action potentials enable rapid propagation of signals. Imbalance of inhibitory and excitatory signals can lead to the development of neurological insults [5–7].

The main inhibitory neurotransmitter, γ-aminobutyric acid (GABA), binds to the ionotropic receptor GABA type A channel ( ) [8–10]. GABA’s role in signalling depends on the intracellular Cl -

concentration, which determines the reversal potential for currents (

). lies close to the resting membrane potential (RMP) [11, 12]. Both and RMP vary between cell types and compartments. The depolarising or hyperpolarising effect of GABAergic signalling is dependent on the relative RMP and . When is high, is less negative and GABA stimulation results in depolarisation when it is low, is more negative and GABA stimulation is hyperpolarising [13, 14]. In healthy adult neuron’s is usually maintained at a low concentration, enabling inhibitory, hyperpolarising GABAergic signalling [15]. This constitutes the main role of GABA in CNS neurotransmission its potential dysfunction in neurological disease due to dysregulated cellular Cl - levels is, therefore, of significant interest. Depolarising GABA potentials, in contrast, are commonly observed in immature and peripheral neurons [16]. Finally, in addition to GABA’s role in hyperpolarisation, it is able to act in a further inhibitory capacity via the mechanism of “shunting inhibition.” This process involves increased membrane conductance as a result of GABA stimulation “short circuiting” nearby excitatory potentials without producing a significant change in membrane potential.

Neuronal is regulated by the Na + -K + -2Cl - cotransporter 1 (NKCC1) and the K + -Cl - cotransporter 2 (KCC2) [17]. Using the Na + gradient generated by Na/K/ATPase, NKCC1 drives Cl - into the cell KCC2, in contrast, is the main Cl - extruder in mature neurons [18]. During development, NKCC1 and KCC2 expression patterns change. In the immature CNS, NKCC1 dominates resulting in high . As maturation proceeds, KCC2 expression increases whilst NKCC1 levels fall (Figure 1) [19, 20]. Mature neurons, therefore, have low causing a shift in from depolarising to hyperpolarising [19, 20]. Thus, KCC2 is a crucial regulator of GABA-mediated hyperpolarisation: an essential component of synaptic inhibition within the adult brain (Figure 2).

signalling shifts from depolarizing to hyperpolarising responses during development. In immature pyramidal cells, R-mediated Cl − currents are outward and depolarising because the relative ratio of NKCC1 to KCC2 activity is high. In mature neurons, increased KCC2 activity gives rise to inward - mediated Cl − currents that hyperpolarize the membrane potential.

Loss of KCC2 activity orchestrates a depolarising shift in and is implicated in cortical development systems such as neuro- and synaptogenesis [12, 21]. The fundamental role that KCC2 downregulation plays in these processes suggests a causal link between Cl - homeostasis and the pathogenesis of neurodevelopmental disorders [22, 23]. Although categorised differently, neurodevelopmental disorders including autism and schizophrenia display phenotypic similarities, most notably high copy number variation [24]. These attributes suggest a genetic link between these diseases.

Excitatory and inhibitory imbalance is implicated in the onset of epilepsy. Biopsies of epileptic tissue have identified excitatory GABA activity in response to loss of KCC2 expression and subsequent increase [25–27]. Similarly, in Huntington’s disease positive rat models, upregulation of NKCC1 and loss of KCC2 caused GABA mediated stimulation to switch from an inhibitory to excitatory response [28]. Collectively, these studies suggest that researching expression patterns of KCC2 may further our understanding of the aetiology of these diseases.

The aim of this review is to evaluate the role of KCC2 in various pathological conditions. Consideration will first be given to the structure of KCC2 how this affects its function and expression is a key component to understanding its role in disease. Attention will also be given to specific diseases in which KCC2 dysfunction is implicated. Finally, KCC2 will be discussed as a pharmaceutical target for neurological diseases.

2. Structure and Diversity of the Cl - Cotransporter KCC2

The KCC2 Cl - cotransporter is transcribed from the fifth member of the solute carrier 12 (SLC12A5) gene family. During alternative splicing, SLC12A5 produces two isoforms: KCC2a and KCC2b [29]. The KCC2a transcript is commonly expressed in the spinal cord between embryonic day (E) 14 and postnatal day (P) 60, whilst KCC2b is greatly upregulated in the hippocampus and the neocortex between E17-P14 [29]. As development progresses, KCC2a expression falls whilst KCC2b is upregulated in the mature CNS. KCC2a is, therefore, the favoured isoform in the immature brain but is eventually dominated by KCC2b in adulthood [30]. Structural differences between these isoforms are localised to the N-terminus where they possess a unique 40 amino acid structure. Despite this, their ion transport activity is almost identical [31]. For the purposes of this review, KCC2 denotes KCC2b.

Although KCC2 is one of the most heavily researched transporters within the CNS, limitations in X-ray analysis have led to poor understanding of its structure and functional mechanisms. Hydropathy blot analysis suggests that KCC2 contains 12 transmembrane domains anchored by intracellular N- and C-termini [32]. Precisely half of the protein is intracellular and is the target for a number of kinases and a single phosphatase (Figure 3). Studies have begun to uncover an integral role of the C-terminus in KCC2 activity [33]. For example, posttranslational modifications - phosphorylation and/or glycosylation have been associated with the extrusive qualities displayed by KCC2 [34–36]. During development, KCC2 assembly becomes more complex, with immature brains displaying a higher monomeric count whilst oligomerisation correlates with maturation [37]. More recently, Agez and colleagues showed that KCC2 exists in a monomeric and dimeric state in solution [38]. The same group also noted that peptide C-terminal tagging of KCC2 caused detrimental functional changes and inactivation when expressed in HEK293 cells [38]. Their findings suggest a crucial role of the KCC2 C-terminus in its activity.

Whilst these findings provide insight into the functional significance of KCC2 structure, they fail to show this effect in a neuronal setting. HEK293 are an embryonic kidney cell line commonly used in the analysis of ion homeostasis. Both KCC2 isoforms are predominantly expressed in neurons of the brain and spinal cord, organs with several physiological and functional differences to the kidney. These differences are evident in the findings of Uravov and colleagues who noted that inhibition of KCC2 mRNA expression differs between neuronal and nonneuronal cells. KCC2 mRNA expression is mediated by RE-1 silencing transcription factor in nonneuronal cells, which represses the SLC12A5 gene [39]. In neurons, however, the transcription factor early growth response 4 (Erg4) is developmentally upregulated, stimulating an increase in KCC2. This indicates fundamental differences in KCC2 expression between cell types [40]. Further research in CNS specific cell types (e.g. neuroblastoma or primary neurons) is required to determine the therapeutic implications of KCC2 expression.

In animal models of traumatic and ischaemic brain injury, KCC2 is reportedly downregulated at both the protein and mRNA levels [41–43]. Six hours after transient forebrain ischaemia, the KCC2 peptide became more abundant in the dendritic regions of pyramidal cells in the cornu Ammonis 1 (CA1) region of the hippocampus, which displayed no evidence of damage. Over an extended time period (48 h after stroke induction), the same cells began to degenerate in a manner that correlated with downregulation of KCC2 and heat-shock protein 72 (HS72). HS72 can exacerbate or attenuate hypothalamic neuronal death depending on its peptide expression levels and is not expressed in the mature brain under standard conditions [44]. Parvalbumin positive interneurons, which exhibit high SLC12A5 gene expression and glutamatergic input, often survive these events even in regions of complete pyramidal cell loss [45]. This suggests that KCC2 expression is also mediated by brain health upregulation of the cotransporter may indicate onset or previous infliction of neurological insult.

3. Neuronal Expression of KCC2

KCC2 is heavily expressed in the mature CNS and is rarely found in peripheral neurons and nonneuronal cells [46–48]. Upregulation of KCC2 is correlated with neuronal differentiation which occurs caudally to rostrally in the CNS [49]. In the rodent CNS, the caudal section, i.e., spinal cord and brain stem, shows little difference in KCC2 expression compared to that observed in the more mature neuron [49–51]. Conversely, rostral regions such as the hippocampus and neocortex display upregulation of SLC12A5 mRNA from birth [49, 52].

Whilst KCC2 clearly displays region specificity within the body, these studies fail to consider variation in the cotransporter’s expression between species. In rats and mice, for example, KCC2 levels remain low resulting in greater [12]. Data collected by Dzhala et al. (2005) showed that a similar expression pattern was present in neonatal humans. Human parietal lobe autopsy specimens displayed high neuronal expression of NKCC1 and low expression of KCC2 but only before the end of the first year of life [11]. Conversely, work conducted by Sedmak et al. (2016) noted KCC2 expression begins much earlier in humans, during the mid-foetal period and increases to levels resembling adult maturity 6 months after birth [53]. Such inconsistencies may be explained by the use of only a single brain region in Dzhala’s study. Alternatively, differences in maturation between humans and rodents may be responsible. Neonatal rat and mice cortices, for example, achieve a developmental stage which equates to the beginning of the third trimester of gestation in the human foetus [54, 55]. Together, these data indicate that KCC2 expression may be considered both species- and age-dependant.

KCC2 protein expression has also been associated with Ca 2+ -dependent mechanisms following neuronal damage [56–58]. Various studies have shown that KCC2 activity is heavily reduced after cleavage at the C-terminal domain by calpain proteases. Hypoxic-ischaemic encephalopathy is considered a major contributor to long-term neuronal damage with an apparent relationship between increased intracellular Ca 2+ and neuronal damage under hypoxic conditions [59]. Calpains are Ca 2+ -dependent proteases. Perinatal mammals exhibit a high calpain/calpastatin (the inhibitor of calpain) ratio. Calpain overexpression or excessive activity has been associated with the symptoms of several neurological conditions including hypoxic ischaemia [60, 61], seizures [57], and epilepsy [62]. KCC2 upregulation is required during neuronal maturation to enhance the inhibitory properties of [12, 21]. This process is, therefore, highly sensitive to excessive calpain activity causing a paucity of active KCC2. Thus, calpains may play a fundamental role in the aetiology of these diseases.

4. Regulation of KCC2 Activity

4.1. Phosphorylation

The activity and expression of KCC2 at the plasma membrane is regulated by phosphorylation. KCC2’s carboxyl-domain is the target for several known kinases and is regularly phosphorylated at the serine 940 (S940) residue. Phosphorylation of S940 decreases KCC2 internalisation maintaining high KCC2 membrane expression [63]. This process is regulated by protein kinase C (PKC) which directly phosphorylates S940 resulting in greater transporter activity [63]. In contrast, dephosphorylation causes a fall in KCC2 activity mediated by a reduction in transporter stability [64]. The S940 residue and PKC activity are, therefore, key components in KCC2 regulation. Modulation of PKC activity by separate pathways, therefore, also indirectly regulates KCC2 activity and Cl - homeostasis. Of note is the neuropeptide oxytocin which was found to increase KCC2 activity and support GABAergic signalling by Leonzino et al. (2016) [65]. Using PKC-inhibitors, Leonzino and colleagues prevented oxytocin mediated KCC2 upregulation suggesting a regulatory role of the neuropeptide in this process [65].

The neurotransmitter serotonin has also been reported to influence KCC2 activity. Serotonin binds and activates the receptor 5-hydroxytryptamine type 2A (5-HT2A) in a process that increases cell membrane KCC2 levels and subsequently restores endogenous synaptic inhibitory mechanisms in mouse models displaying injury to the spinal cord [66]. This serotonin-mediated activity is believed to be PKC-dependent given that PKC inhibitors reduced KCC2 activity [66]. Together, these results suggest S940 phosphorylation is influenced by several pathways. Given the crucial regulatory role of this residue, we can infer that the transporter’s expression oscillates according to a variety of paracrine stimuli. Given the increased cell-surface density of KCC2 during S940 phosphorylation, this may be a particularly promising area of therapeutic study. Therapeutic enhancers of S940 phosphorylation may prove effective in this field especially given the recent finding that KCC2 potentiation can limit onset and severity of neuropathic seizures [67].

The dependence on C-terminal domain integrity displayed by KCC2 makes this domain a potential target for therapeutic treatments. For example, KCC2 membrane stability is heavily reduced when tyrosine residues 903 and 1087 are phosphorylated causing its subsequent trafficking to the lysosome [64]. In addition, the threonine 906 (Thr 906 ) and threonine 1007 (Thr 1007 ) residues display inhibitory characteristics when phosphorylated [68, 69]. During the neonatal period, brain localised Thr 906 and Thr 1007 are often phosphorylated, thereby preventing premature KCC2 activity [68, 69]. Mutants of KCC2, however, commonly show variation at these phosphorylation residues. Mutations at S932 to aspartate (S932D, mimicking phosphorylation) or T1008 to alanine (T1008A, mimicking dephosphorylation) significantly enhance KCC2 activity (up to 1.5-2-fold increase) in HEK293 cells [70]. Mutation at S940 to alanine (S940A, mimicking dephosphorylation) in vivo reduces KCC2 activity and enhances the effects of kainate-induced status epilepticus [36]. In contrast, Thr 906 A/Thr 1007 A double-point alanine substitution enhances KCC2 function in cell culture [67, 68, 71, 72]. Interestingly, Thr 1007 A mutations do not impact KCC2 surface expression. Preventing phosphorylation of Thr 906 and Thr 1007 is, however, sufficient to enhance the Cl - extrusive properties of KCC2 in vivo [67]. Such findings suggest that this is not just the result of increased KCC2 protein but rather multiple processes. The authors hypothesised that these mutations increase KCC2 affinity for Cl - . KCC2 Thr 906 A/ Thr 1007 A variant-carrying neurons reached Cl - equilibrium at a more negative EGABA than the wild type control. When Cl - admittance is low, the increased Cl - affinity displayed by these variants aids extrusion at levels beyond the wild-type threshold [67]. This increase in KCC2 function was sufficient to reduce chemoconvulsant-induced seizure activity and severity [67], suggesting that the cotransporter has therapeutic potential as a seizure limiting drug target.

Recent data provided by Friedel et al. (2015) showed the protein, With-no-lysine kinase 1 (WNK1) stimulated phosphorylation of both Thr 906 and Thr 1007 by means of the Kinase, Ste20-related proline alanine-rich kinase (SPAK) [69]. SPAK was phosphorylated and subsequently activated by WNK1 inhibiting KCC2 activity [69]. SPAK function and phosphorylation may also fluctuate throughout development depending on WNK1 activity [73]. Should phosphorylation of KCC2 residues Thr 906 and Thr 1007 occur in immature brains but fall during development, it may explain why KCC2-dependent Cl - extrusion dominates in the adult CNS [69]. WNK1 is, therefore, a key regulator of KCC2 activity and a potential therapeutic target for the treatment of excitatory/inhibitory disorders.

Interestingly, Friedel et al. (2015) also found that inhibition of WNK1 dephosphorylated KCC2 at Thr 906 and Thr 1007 [69]. This relationship was noted in other studies suggesting a regulatory role of WNK1 in KCC2 activity. KCC2 activity assays showed the amino acid taurine significantly inhibited KCC2 via serine/threonine phosphorylation compared to control and also activated WNK1 [74]. This corroborates Friedel et al. (2015) who showed that inhibition of WNK1 increased extrusion in a KCC2-dependent manner in cultured rat hippocampal and cortical neurons [69]. Genetic studies examining changes in WNK1 activity may elucidate the aetiology of many neurological diseases.

Using the organic compound N-ethylmaleimide (NEM), Conway et al. (2017) increased KCC2 activity through increased S940 phosphorylation and decreased Thr 1007 phosphorylation [72]. Interestingly, NEM was found to potentiate KCC2 activity in neurons, particularly in cells with higher pThr 1007 levels or lower pS940 [72]. Furthermore, KCC2 mutation S932D could abolish further stimulation by NEM, whereas T1008A by another KCC2 activator, staurosporine [70]. Such findings provide valuable insight into therapeutic limitations as drugs that act to modulate KCC2 surface levels or intrinsic conformational change through phosphorylation [33, 34] would only be effective in cases of high pThr 1007 or high pThr 1008 and low pSer 940 or low pSer 932 . These attributes are more common in cases of spinal cord injury. Nevertheless such drugs may be of some use in the treatment of neurological disorders. Despite this limitation, their work suggests that manipulation of Thr 1007 phosphorylation may prove relevant to the advancement of neurological therapeutics.

An independent study identified the regulatory role of five phosphosites Ser 31 , Thr 34 , Ser 932 , Thr 999 , and Thr 1008 using alanine and aspartine mutants [70]. Substitution of Ser 31 , Thr 34 , and Thr 999 did not affect KCC2 activity. Ser 932 D (mimicking phosphorylation) and Thr 1008 A (mimicking dephosphorylation), however, increased transporter activity [70]. In addition, treatment with the known KCC2 activators NEM or staurosporine was ineffective in activating Ser 31 D, Thr 34 A, Ser 932 A/D, Thr 999 A, Thr 1008 A/D or Ser 31 A, Thr 31 D, Ser 932 D KCC2 variants, respectively [70]. These results demonstrated the existence of phosphosensitive sites that regulate KCC2 activities via the integration of various signalling pathways.

4.2. Trophic Factors

KCC2 activity is modulated by a number of trophic (growth) factors including TGF-β2 [75], neurotrophic factor [76], and brain-derived neurotrophic factor (BDNF) [57]. Of these, BDNF is the most well-studied modulator of KCC2 activation.

BDNF is a 27-kDa polypeptide involved in neuronal survival, differentiation, and growth [77]. Its role in KCC2 regulation was first discovered by Aguado et al. (2003) who noted that KCC2 mRNA levels increased with overexpression of the BDNF gene in developing neurons. This process was later found to utilise the Tropomyosin-related kinase (Trk) pathway, as deletion of the TrkB isoform decreased KCC2 mRNA [78]. These data suggest a proregulatory role of BDNF in immature neurons. In mature neurons, however, BDNF downregulates KCC2 at both the protein and RNA levels [79, 80].

Recently, Huang and colleagues noted BDNF-KCC2 regulation was injury dependent. In intact animals, BDNF downregulated membrane-bound KCC2. In animals with spinal cord injury, however, BDNF upregulated the cotransporter [81]. Reasons for these differences are not yet understood, although the authors suggested one hypothesis based on BDNF-TrKB receptor binding. This causes activation of signal pathway components such as PLCγ BDNF downregulates KCC2 in the presence of PLCγ but upregulates it when PLCγ is lacking. Given that spinal cord injury has previously been found to decrease PLCγ expression [80], it may play a logical role in injury-dependent KCC2 regulation. Interestingly, a separate study has shown that BDNF plays a crucial role in KCC2 upregulation after seizure-induced neuronal insult [57]. Together, these studies suggest that targeting BDNF may be of therapeutic value in the treatment of diseases involving KCC2 downregulation.

4.3. Transcriptional and Translational Regulation

KCC2 expression is exclusive to neuronal cells, as dictated by the activity of a neuron-restrictive silencing element (NRSE) acting at the first intron of SLC12A5 [82, 83]. A 1.4 kb promoter fragment is also implicated in KCC2 neuron expression. This was identified in a transgenic model lacking NRSE. Cells lacking NRSE showed increased levels of KCC2 expression and also expressed the active 1.4 kb promoter fragment [39]. The transcription factor Erg4 has since been found to bind to this promotor fragment and regulate KCC2 expression [40]. SLC12A5 also displays a second binding site within its promoter region known as the E-box region, which binds upstream stimulating factors (USF) 1 and 2. USF1 is negatively regulated by amyloid precursor protein (APP) which simultaneously downregulates KCC2 [84]. USF1 is, therefore, a potentially key component in the expression pattern of KCC2. Regulatory proteins such as APP and USF1 may act as biomarkers for the early identification of neurological and epileptic disease.

For successful Cl - extrusion, KCC2 must be expressed at the cell surface. A further role in which APP is implicated is the stabilisation of KCC2 at the cell membrane. Direct binding of APP to KCC2 blocks phosphorylation of the tyrosine residues (903, 1087) which normally promote transporter internalisation and degradation [85]. In this way, APP acts as both a pre- and posttranslational regulator of KCC2 activity and displays strong therapeutic potential for the treatment and/or diagnosis of diseases associated with KCC2 dysfunction.

Surface expression of the KCC2 cotransporter is regulated by kainate receptors, through formation of molecular complexes between the kainate receptor subunit GluK2 and KCC2 [86, 87]. Phosphorylation of Gluk2 by PKC increases KCC2 activity, but PKC can also act directly on the cotransporter due to activation of group 1 metabotropic glutamate receptors (mGluRs). Through induction of Ca 2+ release from internal stores, these receptors increase intracellular levels of the cation [88]. PKC is a Ca 2+ -sensitive kinase meaning its subsequent activation by group 1 mGluRs is an important component of KCC2 recorded activity. In this way, glutamatergic signalling can indirectly enhance inhibitory GABAergic signalling through increased KCC2 activity [88]. This process is implicated in maintaining equilibrium between excitatory and inhibitory signals [88]. Many neurological diseases are attributed to imbalance of these signals. This indirect mechanism of KCC2 regulation, therefore, presents a potential therapeutic pathway for drug targeting.

5. The Role of KCC2 in the Development of Epilepsy

The role of KCC2 mutants in epilepsy development was discovered in two separate studies conducted on patients displaying different epileptic symptoms. The first studied an Australian family suffering from febrile seizures and identified an arginine-to-histidine substitution at position 952. This missense mutation, formally named R952H, caused a substantial decrease in KCC2 membrane expression compared to the wild-type control [89]. The second, conducted by Kahle and colleagues, investigated idiopathic generalised epilepsy in a cohort of Canadian patients displaying the same mutation, c.2855G>A (R952H) [90]. Companion studies noted a significant decrease in Cl - extrusion compared to control indicative of KCC2 impairment [90].

Kahle et al. (2014) also found a second KCC2 variant, R1049C, with a cysteine substitution at the 1049 position. According to in silico bioinformatics programmes, this mutation is predicted to possess pathogenic properties that correlate with KCC2 dysfunction [90]. In accordance with the findings of Puskarjov et al. (2014), Kahle and colleagues showed that R952H mutants had a significantly lower level of KCC2 expressed at the cell surface. In R1049C mutants, however, KCC2 levels were not noticeably different to control [89, 90]. R1049C reduced KCC2 efficacy for Cl - extrusion, resulting in higher basal levels and membrane depolarisation at the previously inhibitory synapse [90]. Both variants also displayed a significant (>50%) decrease in S940 phosphorylation. Thus, both R952H and R1049C C-terminal mutations reduce KCC2 activity. This, in part, may be due to a decrease in stimulatory S940 phosphorylation [90]. Alternatively, interaction of these variants with the ISO domain (a unique 15 amino acid region on the KCC2 C-terminal domain) which has previously been identified as a vital component to KCC2 isotonic activity may cause the observed reduction in KCC2 function [91].

More recently, Stödberg and colleagues identified an autosomal recessive heterozygous loss-of-function mutation in the SLC12A5 gene in children from two separate families [92]. In both families, two children developed clinical features of epilepsy of infancy with migrating focal seizures (EIMFS). All mutated residues were of KCC2b lineage: L288H, L403P, and G528D. Of the four children examined, two had compound heterozygous mutations, c.1208T>C (p.L403P) and c.1583G>A (p.G528D), whilst the others had homozygous missense mutations, c.863T>A (p.L288H) [92]. L403P and G528D mutants displayed complete loss of KCC2-mediated Cl - extrusion, whilst the homozygous L403P mutant had reduced surface expression and glycosylation leading to partial loss of function [92]. Their data further contributes to the growing evidence that disruption of KCC2 activity is implicated in epilepsy. Research into additional mutations affecting SLC12A5 may provide novel insight into the individual application of antiepileptic strategies.

There are, however, limitations to the data collected here that cannot be overlooked. All variants described in these studies were only identified through examination of the SLC12A5 gene sequence. The need for whole genome sequencing intervention to identify other variants or alleles not encoded by SLC12A5 but that augment KCC2 activity was raised by these studies [89, 90, 92].

Another study conducted by Saitsu et al. (2016) also identified four previously undiscovered KCC2 variants that resulted in EIMFS [93]. In a sample of ten sporadic and one familial case of EIMFS, whole exome sequencing identified compound heterozygous SLC12A5 variants in two families: c.279 + 1G > C causing skipping of exon 3 in the transcript (p.E50_Q93del), c.572 C >T (p.A191V) in two siblings, and c.967T > C (p.S323P) and c.1243 A > G (p.M415V) in another individual. Another patient with migrating multifocal seizures carrying compound heterozygous mutations, c.953G>C (p.W318S) and c.2242_2244delTCC (p.S748del), was also identified from whole exome sequencing data of 526 patients and targeting of the SLC12A5 sequence from a cohort of 141 patients with infantile epilepsy [93]. Gramicidin-perforated patch-clamp analysis identified a reduction in Cl - extrusion of E50_Q93del and M415V mutants, with mildly impaired function of A191V and S323P mutants. Membrane expression of these KCC2 variants did not differ from control. Heterologous expression of two KCC2 variants, however, mimicking the patients’ status, showed significantly higher levels than wild-type KCC2 but lower levels compared to the group lacking KCC2 [93]. These findings indicate that even partial disruption to neuronal Cl - extrusion, mediated by two impaired variants of SLC12A5, causes EIMFS.

Since these discoveries, gene panel sequencing of an EIMFS patient from an unrelated family found a compound heterozygous constellation of variants in SLC12A5 consisting of a maternally inherited p.Ser399Leu and a de novo p.Arg880Leu mutation in human KCC2b [93]. Such mutations may be pathogenic.

6. KCC2 in Neurodevelopmental Disorders

KCC2’s C-terminal domain is encoded at the 3’ end of the SLC12A5 gene [90]. Recently, Merner et al. (2015) investigated KCC2 regulatory variation using Sanger sequencing to investigate the coding nucleotides 21-25 of the SLC12A5 gene [94]. The authors screened a total of 427 autism spectrum disorder (ASD), 143 schizophrenic, and 190 intellectual disability cases [94]. R952H and R1049C were among the mutations found in ASD cases. Interestingly, R952H was also implicated in schizophrenia, suggesting overlap between these disorders. Different phenotypic outcomes from R952H mutation (i.e., which disease the patient has) are likely dependent on other allele interactions.

Thorough understanding of how risk alleles contribute to disease is not yet established. In polygenic disease models, causality is never attributed to just one variant [95]. Merner showed that patients with ASD carried rare KCC2 variants that affected CpG sites [94]. CpG sites are prone to methylation, a process that can alter the expression pattern of the gene [96]. Variation in SLC12A5 expression in patients with ASD may, therefore, be the consequence of epigenetic interactions, which represent a potentially valuable focus for future research.

7. KCC2 in Neuropathic Pain

Neuropathic pain (NP) is characterised by spontaneous pain sensations and tactile allodynia. The system of pain detection requires a balance of excitatory and inhibitory signals. When this balance is disrupted either through injury or psychogenic insult, it can lead to NP. In both the spinal cord and dorsal horn, synaptic transmission patterns vary between NP models [97, 98]. This pain has been attributed to dysfunctional inhibitory mechanisms in the spinal cord. In fact, pharmacological disruption of synaptic inhibition within the dorsal horn induces symptoms commonly attributed to NP [99]. Reduction of the Cl - gradient across the neuronal membrane has since been identified as the cause of NP initiated by peripheral nerve injury [100]. This is the result of downregulation of KCC2. During NP pathogenesis, an array of cellular mechanisms converge causing a reduction in KCC2 expression and function and increase in neuronal [100]. The need to identify cellular mechanisms that increase KCC2 activity during neuropathic episodes is, therefore, crucial to the advancement of therapeutics in this field.

Increasing KCC2 activity presents a very prudent area of research [101–103] the ability to restore normal inhibitory function in neurological conditions associated with impaired Cl - transport may prove to be an effective therapeutic strategy. High-throughput screening assays have now identified KCC2 activators that reduce . Gagnon et al. (2013) optimised a first-in-class arylmethylidine family of compounds (CLP257) to lower [104]. CLP257 rescued KCC2 plasma expression, renormalised stimulated recall responses in spinal nociceptive pathways sensitized after nerve injury, and reduced hypersensitivity of NP rat models [104]. The results of Cardarelli et al. (2017), displaying CLP257 as a direct KCC2 activator, were not replicable [105] but do reveal the compounds’ ability to potentiate activity [105]. Furthermore, - dependent synaptic inhibition by KCC2 antagonist, gabazine could actually tune KCC2 activity via the Cl - -sensitive WNK1 kinase [106]. Oral treatment of the CLP257 prodrug equivalent, CLP290, showed similar efficacy to their control of pregabalin, a drug commonly used in the treatment of epilepsy and anxiety [104, 107]. Side effects of pregabalin include dizziness and sedation causing motor function disturbance [107]. Such side effects were not present during treatment with CLP290 [104]. These results highlight KCC2 as a plausible target for NP drug therapy and may provide further insight into the treatment of other neurological disorders.

8. Therapeutic Potential of KCC2

KCC2’s interaction with Cl - importer makes it a potential target for the treatment of several neurological diseases. Currently, phenobarbital (PB), a barbiturate that delays the closing of , is the most common first-line drug used for the treatment of seizures [108]. Hypoxic-ischaemic encephalopathy is a major contributor to the onset of neonatal seizures, with over 50% of patients displaying electrographic seizures even after treatment with PB [109]. Interruption to the expression and/or function of either KCC2 or NKCC1 affects the antiseizure efficacy of agonists [110]. The higher within immature neurons potentially contributes to resistance to pharmacological first-line antiseizure agonists in the immature brain [111].

Recently, a translational model for age-dependent PB-resistant seizures was developed by Kang et al. (2015) [112]. Using a permanent unilateral carotid-ligation model of neonatal ischaemic-seizures in CD-1 pups, the authors investigated the ability of the NKCC1 antagonist bumetanide to rescue PB-resistance. Bumetanide failed to rescue PB as an antiseizure therapeutic [112]. A number of preclinical models show that the severity of seizure and mechanism of damage can influence the efficacy of antiseizure drugs and alter cotransporter expression [113–116]. Kharod et al. (2018) noted model-specific insults modulated both expression and function of the NKCC1 and KCC2 cotransporters. Using a pentylenetetrazol-induced seizure model, they identified a significant upregulation of KCC2. In contrast, ischaemia-induced seizures significantly downregulated KCC2 [117]. These data combined reveal KCC2 expression to be insult specific and may explain why some anticonvulsant therapies display variable efficacy during first-line treatment.

Activation of the Trk isoform TrkB has been shown to induce phosphorylation of phospholipase C-γ1 which is linked to the downregulation of KCC2 and development of epilepsy [118, 119]. Carter et al. (2018) showed that TrkB antagonist, ANA12, increases the efficacy of PB in CD1 mice at doses as low as 2.5 mg/kg. ANA12 also rescued KCC2 expression after postnatal ischaemia [120]. Unlike current clinical antagonists (e.g. bumetanide, furosemide), ANA12 is capable of passing through the blood-brain-barrier [121], allowing it to have greater therapeutic impact on KCC2 activity as this has previously been a limiting factor for treatments [122]. ANA12 may, therefore, have therapeutic benefit by preventing downregulation of KCC2, thus maintaining low .

9. Conclusion

KCC2 is a key player in the maintenance of neuronal Cl - homeostasis. A plethora of studies identify KCC2 dysfunction and misregulation as a key component in the development and onset of many neurological diseases. KCC2 is a strong candidate for therapeutic targeting and should be further considered by pharmaceutical investors. It should be noted that the majority of these findings are not made in human neuronal cell lines and are, therefore, limited in their ability to determine the immediate effects of targeting KCC2. Despite this, the data collected from human participants indicates that there is a place for KCC2 pharmaceuticals in the treatment of epilepsy. Continued research in human neuronal cell types may reveal more opportunities for drug development.

Conflicts of Interest

The authors declare that there are no conflicts of interest regarding the publication of this paper.


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3. Analysis Procedures

3.1. General Procedures.

Spike times were detected from recorded voltage traces as the time the membrane potential crossed 0 mV from below. The firing rate was the number of spikes recorded during a trial, averaged across all similar trials and normalized by the duration of the trial in seconds.

Each row of the rastergram represented a spike train from a different trial. Each spike was represented as a tick or a dot, with the spike time as the x-ordinate and the trial number as the y-ordinate. The trials were often grouped together based on the stimulus amplitude or reordered based on which pattern they belonged too. This is indicated in each figure caption.

The spike time histogram is an estimate of the time-varying firing rate. It was obtained by dividing the time range of a trial into bins (typically 1 or 2 ms wide) and counting the number of spikes that fell in each bin across all trials. The bin count was normalized by the number of trials and by the bin width in seconds. The latter normalization ensured that a bin entry had the dimensions of a firing rate, Hz. The histogram was subsequently smoothed by a gaussian filter with a standard deviation equal to 1 bin size.

Events were detected using the procedure detailed in section 4. At the end of this procedure, all spikes were either assigned to an event or were classified as noise. The unitless event reliability is the fraction of trials on which a spike was observed during that event, and the event jitter (ms) is the standard deviation of the spike times belonging to the event. The event precision (1/ms) is the inverse of the event jitter. For a given amplitude, the reliability, precision, and jitter are defined as the event reliability, event precision, and event jitter averaged across all events.

We used three techniques to find an event: the Victor-Purpura distance, the fuzzy clustering method, and classification entropy and mutual information.

3.2. Calculation of the VP Distance.

Briefly, the Victor-Purpura (VP) metric (Victor & Purpura, 1996) calculates the distance between two spike trains A and B by calculating the cost of transforming A into B (or B into A—the measure is symmetric). This distance is obtained as the minimum cost of transformation under the following rules: adding or removing a spike from A costs +1 point, while sliding spikes forward or backward in time by an interval dt costs q times |dt|. The variable q represents the sensitivity of the metric to the timing of spikes and is expressed in units of 1/ms. For large q values, it is frequently cheaper to add and remove spikes than to move them. Hence, for large q, the metric is simply the number of spikes with different times between the two trains. For small q values, spike-moving transformations are cheap, leaving the majority of the metric's value to the difference in the number of spikes that must be added or removed to produce spike train B in the limit, the metric becomes the difference in the number of spikes in each spike train. For a set of N spike trains, the VP metric produces a symmetric N × N matrix. The (i, j) entry of the matrix is the VP distance between the ith and jth spike trains.

3.3. Fuzzy Clustering Algorithm.

Fuzzy c-means (FCM) was used to cluster trials into groups that had similar spike timings. FCM can be understood by first considering K-means clustering (also, but less commonly, referred to as c-means). In a K-means clustering, a number of clusters is chosen, and the objects to be clustered are assigned on a random basis to each of the potential clusters (Duda, Hart, & Stork, 2001). The name of the algorithm derives from the convention that the number of clusters is denoted by K, but here we denote it instead by Nc for notational consistency. The mean of each cluster is found by using these assignments. Then, using these means, objects are reassigned to each cluster based on which cluster center they are closest to. This process repeats until the cluster centers have converged onto stable values or a maximum iteration count is reached. This type of clustering minimizes the sum of the squared distances of the clustered objects from their cluster means. FCM functions in the same way, but rather than belonging to any particular cluster, each object i is assigned a set of normalized probabilities uij of belonging to cluster j (Bezdek, 1981). This is equivalent to minimizing a nonlinear objective function of the distances of the objects from the cluster centers, characterized by the “fuzzifier” parameter, which is set to 2. After the algorithm converges, each spike train is assigned to the cluster to which it is most likely to belong (maximizing the uij with respect to the cluster index j). A more complete description is given in Fellous, Tiesinga, Thomas, and Sejnowski (2004).

We use FCM on the columns of the pair-wise distance matrix (see section 3.2) because similar trials will have a similar distance from all other trials and are thus represented by similar columns (Fellous et al., 2004). The computational effort of FCM increases with the number of vectors (Ntrial), as well as the dimensionality of the vectors (also Ntrial). Hence, we reduced the dimensionality from Ntrial to 10 components using principal component analysis (PCA) (Jolliffe, 2002). These components accounted for at least 80% of the variance and resulted in clusterings that were similar to those obtained using all principal components.

3.4. Calculation of Entropy and Mutual Information Between Classifications.

2 Parametric Model of CA3-CA1 Signal Transformation

2.1 Schaffer Collateral Presynaptic Model

2.2 Schaffer Collateral Postsynaptic Model

10 pS
1 ms
0.4 ms
0 mV
30 pS
55 ms
is the membrane potential of the dendrites. The conductances of the GABA and GABA receptors are expressed as the biexponential functions

2.4 Feedback Disinhibition

2.5 Synaptic Integration and the H-H Model

wv0puPrw5CL1g__&Key-Pair-Id=APKAIE5G5CRDK6RD3PGA" /> in our model is treated as the integrated value rather than the membrane potential from a specific synapse. To model the dynamic processes for the generation of an action potential (AP) by a CA1 cell, we adopt the classic Hodgkin-Huxley (H-H) equations (Hodgkin & Huxley, 1952). The total current injected into the H-H model is

1 uF/cm
12 mV
115 mV
10.6 mV
36 mS/cm
120 mS/cm

FIG. 3.Dependence of the path length on the arbor span. A: in the optimal dendritic arbor, dendritic branches are fully stretched so that the path length from a dendritic site to the soma is on the same order as the arbor span. B: in a hypothetical dendritic arbor defined by a random-walk trajectory, orientations of dendritic segments are statistically independent and ℓ ∼ R 2 .

Third, we calculate the arbor mesh size—a parameter that quantifies the sparseness of an arbor—by dividing the arbor area by the total length, A/L. By combining Eqs. 14 and 17, we find that

A compact branching arbor is less costly than other branching arbors with the same potential convergence. Consider a sparse arbor, the mesh size in which is much larger than 2s + 〈dd〉 (Fig. 2C), and which does not form potential synapses with every axon passing through the arbor (Fig. 2C). A compact arbor is less costly because it has a smaller span than that of a sparse branching arbor. A compact branching arbor is also advantageous to a dense branching arbor, in which the arbor mesh size is much smaller than 2s + 〈dd〉 (Fig. 2D). A dense branching arbor can form more than one potential synapse with each axon passing through the arbor (Fig. 2D). Given the same number of axons forming potential synapses with the dendrite, such design makes the total dendritic length greater than that in the compact arbor.

How does this analysis of a planar dendritic arbor generalize to three-dimensional (3D) dendritic arbors? When axons run in different directions and the arbor is 3D, the above-cited results still hold if numerical factors of order one are ignored. Yet when these numerical factors are included, a planar arbor is preferable. A planar arbor can be viewed as a two-dimensional (2D) projection of a 3D arbor and the projection is always shorter than the original. Thus both the minimum path length (ℓ) and the minimum total dendritic length (L) in a planar arbor are shorter than those in a 3D arbor.


We thank Asipu Sivaprasadarao for the DN-KATP plasmid, Daryl Davies and Miriam Fine for the GlyR plasmid, Manoj Bhasin and Marie Bruno-Joseph for assistance with the microarrays, and Joan Lemire for comments on the manuscript. We gratefully acknowledge the support of NSF (EBICS sub-award CBET-0939511), the G. Harold and Leila Y. Mathers Charitable Foundation and the AHA (14IRG18570000), the NIH (RO1 AR005593 R01 AR061988), and the W. M. Keck Foundation. The authors declare no conflict of interest.

Additional Supporting Information may be found in the online version of this article at the publisher's website:

Figure S1. Subnetwork enrichment analysis of Xenopus dataset identified (A) regulated genes that are involved in adipocyte differentiation and (B) regulated genes that are involved in the immune system. Acronyms can be found in Appendix S5. Gene functions can be found in Table S1.

Figure S2. (A) Subnetwork enrichment analysis of the human database identifies regulated genes that are involved in BMP2 signaling. Acronyms can be found in Appendix S4. (B) Subnetwork enrichment analysis of the axolotl database identifies regulated genes that are involved in calcium signaling. Acronyms can be found in Appendix S5. (C) Subnetwork enrichment analysis of the human dataset identifies regulated genes that are involved in calcium signaling. Acronyms can be found in Appendix S5. (D) Subnetwork enrichment analysis of the Xenopus database identifies regulated genes that are involved in chloride transport. Acronyms can be found in Appendix S5.

Figure S3. Subnetwork enrichment analysis of the axolotl database identifies (A) regulated genes involved in Huntington disease pathway and (B) regulated genes involved in Parkinson disease pathway. Acronyms can be found in Appendix S5.

Table S1. List of genes from subnetwork enrichment analysis of Xenopus genes involved in organogenesis.

Table S2. List of cell signaling pathways from subnetwork enrichment analysis that are common to all three (frog, axolotl, and human) datasets.

Appendix 1. Entire list of differentially expressed genes in response to depolarization from all three species, frog, axolotl, and human.

Appendix 2. Entire list of enriched cell processes in response to depolarization from all three species, frog, axolotl, and human.

Appendix 3. Entire list of enriched expression targets in response to depolarization from all three species, frog, axolotl, and human.

Appendix 4. Entire list of enriched disease networks in response to depolarization from all three species, frog, axolotl, and human.

Appendix 5. Entire list of gene acronyms used in the depiction of gene networks in the figures.

Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

What is the correct value of Neuronal Resting Potential - is it -65mV or -70mV? - Biology

1. Which of the following is not correct?

P. cytoskeleton present in eukaryotic cell and absent in prokaryotic cells

Q. Streaming, endocytosis and exocytosis only occur in eukaryotic cells

R. Circular DNA in cytosol only occur in prokaryotic cells

S. First eukaryotic cell on earth born more than 3 billion years ago

2. Which one of the following arrangement of the metal ions Na, K, Mg and Ca in the order of decreasing

concentrations is correct with respect to a quiescent mammalian cell?

3. Which of the following is correct statement? In an animal

a) Concentration of sodium is high inside the cell than outside

b) Concentration of calcium is high inside the cell then outside

c) Concentration of potassium is high inside the cell than outside

d) Concentration of magnesium is high inside the cell than outside

4. When the plant tissue is homogenized and were used for analysis of chloroplasts from nuclei. Which

of the following methods may be suitable

a. Polyacrylamide gel electrophoresis

b. Differential centrifugation using sucrose gradients

c. Equilibrium density gradient centrifugation on CsCl gradient

5. In the fluid-mosaic model of the membrane

a) The protein is arranged in layers

b) The lipid has no specific arrangement

c) The lipid is fluid and arrange din a bilayer with functional protein embedded in them

d) Lipids and proteins are not arrange din any particular order

6. According to Robertson’s unit membrane model of plasma membrane

a) Proteins on cytoplasmic and non-cytoplasmic sides are same

b) All proteins are transmembrane proteins

c) There is no space between lipid bilayers

7. The primary thermodynamic factor that favors the formation of a lipid bilayer in aqueous surrounding

8. In biological membrane, integral protein and lipids interact mainly by

c) Hydrophobic interactions

9. What property of bio membrane is responsible or their self-sealing nature?

a) hydrophilicity of phospholipid head group

b) Presence of protein in biomembranes

c) Presence of cholesterol in biomembranes

d) hydrophobicity of the fatty acid side chains of phospholipids

10. The most abundant lipids in plasma membrane is

11. The formation of multivalent at meiosis in diploid organism is due to

d) reciprocal translocation

12. Cells having secretory in function have abundant

13. According to model of Singer and Nicholson plasma membrane is having

a) protein extends inside and outside of lipid bilayer

b) lipid extension outside and inside of protein layer

c) deposition of fat granule between two protein molecules

14. Cell wall of gram positive bacteria is made up of

15. The chloroplast of algae usually lack

16. Which of the following lipids is commonly found in biological membranes?

17. A poikilothermic organism living in the Arctic would have, compared to that organisms living in the

Temperate climate zone, have plasma membrane rich in

d) unsaturated fatty acids

18. The types of sugars commonly present in the cell membrane of RBC are

19. Caelyx are examples for stealth liposomes they are used for as delivery vehicle for the drugs, a water soluble drug is enclosed in the fluid filled interior chamber and a lipid soluble drug in the lipid bilayer. Which of the following statements are correct about the liposomes?

P. They are also used for protein delivery to study the protein functions

Q .A lipolytic enzyme was embedded in the membrane that helps in disintegration of liposome when

R. contains a hydrophilic polymer (PEG) to protect itself from destruction by immune cells

S. They are made of two bilayers that can fuse with the host membrane

20. The role played by phosphotidylethanolamine concentrated in the inner leaflets of the membrane is

P. maintain curvature of the membrane

Q. facilitate transport substances lipid solubility into the membrane

R. facilitates membrane budding and fusion

S. facilitating assembly of cholesterol molecules

21. The main function of phosphatidylinositol present in the inner layer of the lipid bilayer is to

a) facilitate transport substances lipid solubility into the membrane

b) transfer of stimuli from plasma membrane to cytoplasm

c) binding positively charged lysine and arginine residues, such as those adjacent to the membrane

spanning a helix of glycophorin A

22. Which of the following statement is true about biological membranes?

a) membranes consist of only cholesterol and proteins

b) all membrane protein are glycoproteins

c) phospholipids and proteins are the main components of biological membranes

d) all membranes have the same lipid to protein ratio

a) closed, solvent filled vesicles have a single bilayer of fatty acid chain

b) closed, solvent filled vesicle have a single layer of fatty acid chain

c) a structure made up of protein

24. The distribution of transmembrane protein is the plane of cell membrane can best be visualized by

which one of the following

a) thin section electron microscopy

b) freeze-fracture electron microscopy

c) scanning electron microscopy

d) SDS gel electrophoresis

25. A chemical molecule similar in cholesterol function, found commonly in the fungal cell walls is

d) cyclopropane fatty acids

Membrane transport and potential

1. The order of the predicted rate of diffusion across a lipid bilayer (highest to lowest) is

a) Toluene, galactose, phenylalanine and chloride ion

b) Chloride ion, phenylalanine, galactose and toluene

c) Galactose, phenylalanine, chloride ion and toluene

d) Toluene, phenylalanine, galactose, chloride ion

2. All membrane processes, such as pumping and channeling of molecules are carried out by

3. Free fatty acids enter cell by

b) Primary active transport

c) Cannot enter into the cell

d) Secondary active transport

4. Valinomycin, a cyclic peptide

P. Acts as ionophore Q. facilitates passive transport of cation R. act as carrier of K+ transport S. facilitates passive transport of cation

5. Diffusion across the plasma membrane is more rapid if a substance is

c) High in its oil: water partition coefficient

d) Large and globular in shape

6. The rate of movement of a molecule in the plasma membrane depends on the

P . is a heterodimer composed of an alpha subunit and glycoprotein beta subunit

Q. contains alpha subunit which is responsible for ATP hydrolysis and ion pumping

R. contains multipass transmembrane alpha subunit

8. Receptor mediated endocytosis from plasma membrane required which of the following coat proteins?

9. The hyperpolarization of the cell membrane associated with the

a) Activation of voltage-gated K+ channels

b) Activation of the Na+ leaky channel

c) Activation of Ca2+ voltage gated channel

d) Activation of voltage-gated Na+ channels

10.The changes in the electrical potential of a neuron that constitute the action potential occur in the following order

a) Depolarization ----resting potential ---hyperpolarization---resting potential

b) Resting potential---depolarization ---hyperpolarization---resting potential

c) Resting potential ---hyperpolarization---depolarization---resting potential

d) Resting potential ---hyperpolarization---resting potential ---depolarization

11.Nicotinic acetylcholine receptors

P. expressed in muscle cells is a ligand-gated channel

Q. present on postsynaptic membrane

R. contain alpha subunit that binds to the acetylcholine

S. allow passage of both Na+ and K= ions in hydrated form

12.The hair cells of the inner ear are responding to the sound they receive, this could be possible by the presence of which one of the transport system?

13. KcsA, is an example for mechano sensitive channel present in bacteria, that is specific for K+ ions, in the pore region of the channel a short pore helix that extends approximately one third the width of the channel and a non-helical loop that forms the lining of a narrow selectivity filter, that contains highly selective penta peptide that allows only K ions

14. Fibroblasts and most other non-neuronal cells exhibit it an inside-negative electric potential. However, when they are depolarized, fibroblasts do not produce an action potential even though the concentrations of Na+ and K+ inside and outside fibroblasts are identical to those associated with neurons. Fibroblasts not generate an action potential because

a) absence of voltage gated ion-channel

c) Its membrane have large number of porin

d) Its voltage gated Na+ ion channels work at very high rate

15. A common isoform of facilitative glucose transporter present in the skeletal muscles and adipocytes, that is highly responsive to insulin production is

1. Which of the following statement is correct for the endoplasmic reticulum (ER)?

a) The SER is the site for the synthesis, modification and sorting of proteins

b) The RER is the site for lipid biosynthesis

c) The RER is the site for the modification and sorting of proteins

d) The RER is the site for protein synthesis and SER is involved in modifications and sorting of proteins

2. Which of the following are functions of RER?

P. Splicing of polypeptide

Q. Formation of disulfide bond

R. Glycosylation of proteins during translation

S. Assembly of multisubunit proteins

3. Ca 2+ ATPAse, present on sarcoplasmic reticulum, increases CA2+ concentration in

a) Sarcoplasmic reticulum as compared to cytosol actively

b) Cytosol as compared to sarcoplasmic reticulum

c) Sarcoplasmic reticulum as compared to cytosol passively

4. The oligosaccharide part of glycoprotein is either N-linked or O-linked. The amino acid residues through which these oligosaccharides are attached to polypeptides are

5. Which one of the following statement is not true to protein glycosylation?

a) Protein glycosylation is one of the major biosynthetic functions of SER

b) It is a process of covalent addition of sugars to secretory proteins

c) An oligosaccharide containing 14 sugars is transferred to the NH2 group of asparagines residue of a protein

d) Antibiotic tunicamycin inhibits the first step of N-linked glycosylation

6. Microsomal cytochrome P450

Q. are membrane bound xenobiotic metabolizing enzymes

S. catalyzes diverse reaction such as hydroxylation, sulfoxidation, epoxidation

7. Choose the statement that is not correct for golgi apparatus of the cell

a) Degradation of xenobiotic compounds occur in golgi apparatus

b) Golgi apparatus has cis and trans faces

c) Golgi apparatus is predominant in cells that are specialized for secretion

d) It is involved in oligosaccharide modification

8. The presence of abundant golgi vesicles near cell plate in the middle of a plant cell at the late telophase and cytokinesis of mitosis reflects the role of golgi complex in

a) Lysosomal enzyme targeting

b) Polysaccharide synthesis

d) Uptake of membrane lipids

P. contains a series of stacked internal cisternae

Q. is a polar organelle with its cis face close to the ER and its trans face close to the plasma membranG

R. contains the same enzymes in all its pars

S. is the site of further modification of preformed oligosaccharides to make complex oligosaccharides

10.Marker enzyme of golgi apparatus is

11.If cells are broken up and subjected to sedimentation using centrifuge, the new structure formed is

Q. maintain turgor pressure

R. perform autophagy and solute accumulation

a) A single lysosome surrounds a single cell organelle

b) Cellular constituents are recycled

c) Internal membranes can be synthesized

d) Mitochondria are assembled

14.Which of the following is incorrect about signal recognition particle?

a) It is ribonucleoprotein

b) It is made up of six polypeptide

d) It acts as molecular chaperone

15.During the synthesis of secretory proteins the following events happen

1. The signal recognition particle (SRP) binds to the signal sequence

2. The two parts of a cytosolic ribosome binds to the mRNA

3. Protein synthesis stops

4. The signal sequence is translated

5. The ribosome and protein are transferred to a Translocon

6. The secretory protein folds

7. The signal sequence is cleaved by a signal peptidase

8. The SRP binds to its receptor in the ER membrane

The correct order for these events is

16.Which of the following show correct order of the secretory pathway?

a) RER –Golgi—Secretory vesicle – cell exterior

b) SER—Golgi—Secretory vesicle –cell exterior

c) Golgi—SER—Secretory vesicle—cell exterior

d) Golgi—Gysosomes-- SER—secretory vesicle—cell exterior

17.Plant cell walls contain a proline rich protein. A plant cell is pulsed with radioactive proline and then chased with non-radioactive proline for growth. After various period of chase, cells are fixed and prepared for autoradiography. The labeling of cell compartments is followed.

If the sequence of events in the plant cell is the same as that of animal cell, the order of labeling of cell compartment will be

18.Choose the correct statement

P. signal sequence present near N-terminus of polypeptide is rich in hydrophobic amino acids

Q. BiP is a chaperone present in the lumen of RER

R. COPI coated vesicles transport proteins in the retrograde directions from golgi to RER

S. mannose-6-phosphate receptors in the membrane of the trans-golgi bind proteins bearing mannose-6-phosphate and direct their transfer to lysosome

19. Docking and fusion of transport vesicles with their target membrane involves

P. each V-snare is a vesicular membrane binds to a cognate t-SNARE in the target membrane

Q. SNARE complex is disassembled in an ATP-dependent reaction

R. GTP-binding protein, the Rab protein, regulate docking of vesicles with the correct target membrane

S. NSF-catalyzed hydrolysis of ATP then drives dissociation of the SNARE complexes

20. In which of the following does the inner surface of a closed membrane or vesicle become the outer surface of a closed membrane or vesicle

a) Fusion of two intracellular vesicles

b) Transfer of an endoplasmic reticular membrane into golgi membrane via vesicle

c) Exocytosis of a secretory vesicles

d) Division of a bacterial cell

21. Choose the incorrect statement about mitochondrial protein targeting

P. Matrix-targeting sequences located at the N-terminus

Q. Matrix-targeting sequences rich in negatively charged acidic residues

R. Matrix-targeting sequences rich min hydrophobic and positively charged basic amino acids

S. Translocation into matrix is driven by the protein-motive force across the inner membrane and

ATP hydrolysis by the Hsc70 ATPase in the matrix

22. Which of the following is/are not true about myosin?

P. Myosin has an actin-binding site

Q. Myosin has a GTPase site

R. Myosin has an ATPase site

S. Myosin walks towards the minus-end of the microtubule

23. Evidence that mitochondria originated from an endosymbiotic relationship between aerobic

bacteria and ancestral eukaryotic cells includes the following except

a) DNA in mitochondria is not packaged by histones

b) Mitochondrial DNA is circular like prokaryotic DNA

c) Protein synthesis in mitochondria is inhibited by antibiotics as in bacterial protein synthesis

d) Ribosomal RNAs in mitochondria code for prokaryotic like ribosomal proteins

a) SRP – bring proteins and the ribosomes that are translating them from the cytosol to the rough ER

b) KDEL sequence – targets protein emerging from the golgi apparatus to rough ER

c) Chaperones – assist in protein folding

d) eIFs – help in translocation of ribosome on mRNA

25. Proteins that are to be used outside the cell in eukaryotes are synthesized

b) On the rough endoplasmic reticulum

c) On the smooth endoplasmic reticulum

26. Nuclear localization signals

P. rich in basic amino acids

Q. Rich in acidic amino acids

27. The role of calcium in muscle contraction is to

a) Break the cross-bridges as a cofactor in the hydrolysis of ATP

b) Bind with troponin, changed its shape so that the action filament is exposed

c) Transmit the action potential across the neuromuscular junction

d) Spread the action potential through the T tubules

28. The nucleolus is the site where

a) Ribosomal RNA is transcribed and ribosomes are assembled

c) Protein recently imported from the cytoplasm are deposited

29. Chloroplast is absent always in

a) Chlamydomonas nivalis and Chlamydomonas coccifera

b) Oscillatoria cripsa and apical cell of spirogyra

c) Rivularia and basal cell of Ulothrix

d) Terminal cell of Oedogonium and basal cell of Ulothrix

30. Which one of the following is NOT a neurotransmitter?

31. Lysosomal protein targeting takes place through

b) Clathrin coated vesicles

d) Receptor mediated endocytosis

32. Which one of the following protein is involved in the nucleation step of microtubules in vivo?

33. Histones have very high percentage of arginine and lysine residues, For this class of protein, which one of the following reagents should be a suitable choice for generating peptides in the determination of the aminoacids sequence of the protein?

34. Mast cells contain vesicles that store large amounts of histamine. After staining with eosin, these vesicles are stained red in colour. Identify which of the following interactions is involved between histamine and eosin?

a) Hydrophobic interaction

b) Electrostatic interaction

35. Choose the statement that is NOT correct for the cytoskeletal protein actin

a) a -actins are found in various types of muscles

b) Polymerization of pure actin in vitro required GTP

c) Actin filaments have a slow growing minus end and fast growing plus end

d) Cytochalasins are inhbitors for actin polymerization

36. In chemical synapse, receptors for neurotransmitters are found on

d) Myelin sheaths enveloping axons

37. Which of the following is single membrane structure

38. Primary lysosomes in a cell are formed by

39. The electric potential gradient inside and outside of the plasma membrane is

a) 60 mv and 90 mv approximately

b) 30 mv and 15 mv approximately

c) 15 mv and 30 mv approximately

d) 90 mv and 60 mv approximately

40. Breaking of acrosome membrane is technically termed as

41. Lysosome has a pH optimum centered around pH 5. The active site of lysozyme contains a glutamic acid residue (pKa =5.5) and an aspartic acid residue (pKa=4), which of the following statement is correct about eh mechanism of lysozyme?

a) The glutamic acid residue is in a more polar environment than the aspartic acid

b) During the entire catalytic mechanism, the aspartic acid residue remains unprotonated

c) During the mechanism , an oxyanion transition state forms

d) The glutamic acid residue acts as a general base catalyst

42. All the following cellular events involve action filaments except

b) Cytokinesis in animal cells

c) Flagellar movement in bacteria

d) Contraction of smooth muscle

43. Ca2+ is important in skeletal muscle contraction because it

a) Activates the myosin ATPase by binding it

b) Binds to troponin to remove a constant inhibition of cross-bridge attachment

c) Prevents the formation of bonds between the myosin cross bridges and the actin filament

d) Is required to detach the myosin head from the action filament

44. Glycophorin, an integral membrane protein, has a single transmembrane alpha helix, which of the following idealized hydropathy plots most likely represent the transmembrane nature of glycophorin[Saran1] ?

45. Integrins are transmembrane proteins that connect

a) The nuclear lamina to cytoplasmic kinase

b) The extracellular matrix to the cytoskeleton

c) Focal adhesion to hemidesmosomes

d) Microtubules to action filaments

46. Rhodopsin, b -adrenergic receptors, and muscarinic acetylcholine receptors share which of the following features

a) Each causes an inhibitory intracellular response

b) Each activates a tyrosione kinase cascade

c) Each is composed of an a b - dimer

d) Each functions through a heterotrimeric G protein

47. Cholera toxin causes massive and often fatal diarrhea by

a) Inactivating G1 protein

b) Irreversibly activating adenylate cyclase

c) Locking Gs protein into an inactive form

d) Rapidly hydrolyzing G protein GTP to GDP

48. Specific recognition between cell types such as leucocytes and endothelial cell of blood vessels is mediated by cell-surface glycoproteins called

49. Pick the correct statement

a) In O linked glycosylation, sugars are attached to the protein via O-glycosidic bonds to the carboxyl groups of Asp and Glu

b) In O-linked glycosylation performed oligo-saccharides are attached to the relevant protein

c) In O-linked glycosylation, N acetyl-galactosamine is added via O-glycosidic bonds to the Oh groups of Ser and Thr after which other sugar are added sequentially

d) O-linked glycosylation is inhibited by the passage of the newly synthesized protein through the golgi complex

50. If a subcellular fraction from liver tissue exhibits high level of acid phosphatase activity, it enriched

51. The non-membranous organelles of a cell is

52. The iron containing protein, transferrin, is taken up by fibroblast cells in culture. In what order will the iron atoms of this molecule follow the heterophagy pathway

P. coated vesicle at cell surface

Q. maintain turgor pressure

R. perform autophagy and solute accumulation

54. Neonatal adrenoleukodystrophy (NALD) is a severe neurological, visual and liver disorder effects is caused due to the disorder of the peroxisomes is an

P. autosomal recessive disease

Q. disease arise due to mutation in the peroxisomal DNA

R. disease arise due to mutations in the nuclear gens

S. disorder due to defective or absent of specific peroxisomal proteins

55. Which of the following is not TRUE about the Type-IV based integral membrane protein

a) Multipass membrane protein having both N –terminal and C-terminal in same side or opposite side of the membrane

b) Contains many stop transfer sequences

c) The topogenic sequence is a single pass membrane protein

d) b -adrenergic receptor is an example for this type

56. The proteins that are need to be destined to endoplasmic reticulum are transported from the Cis face of the golgi and they found to have some specific sequence on the C-terminus region, which serves as a sorting signal to get it grouped as resident protein, that signal possess the following amino acids

b) KDEL in one letter code

57. Actin filaments and microtubules share all of the following properties except

a) They are involved in cell motility

b) They are intrinsically polar structure

c) They can associate with motor proteins

d) They are assembled from subunit that are heterodimers

58. A monoclonal antibody binds to G-actin but not to F-actin, what does this binding says about the epitope nature recognized by antibody?

a) The epitope in F-actin induce an enzymatic activity inactivating mAb

b) The epitope in F-actin is surrounded by myosin thus no mAb interaction is observed

c) The epitope is likely to be a structure that is buried when G-actin polymerizes to from F-actin

d) A peptide fragment released from F-actin blocks the mAb interaction with the epitope

59. Which of the following statement is wrong?

a) Svedberg unit are not additive

b) The greater the mass, the faster the rate of sedimentation

c) The greater the mass, high the S-value

d) The ribosome of given cell compartment are different

60. The marker enzyme of mitochondria is cytochrome oxidase, however, for lysosomes it is

a) Succinate dehydrogenase

61. Vacuoles present in plant cells are analogous to

62. Which one of the following is NOT a function of RER?

a) N-linked glycosylation of proteins

b) Folding of polypeptide chains

c) O-linked glycosylation of proteins

d) Specific proteolytic cleavage

63. Membranes of the two organelles are always likely in contact

c) Golgi and plasma membrane

64. Kinesin is correctly described as

a) An enzyme that phosphorylates intermediated filament proteins

b) A co-factor with cyclin-B in the control of cell cycle events

c) A motor protein that helps vesicles to move along microtubules

d) An actin associated protein involved in the control of movement

65. The process of microtubules shrinking or expanding is determined by

a) The rate of GDP-bound tubulin addition relative to the rate of tubulin GTP hydrolysis

b) The phosphorylation state of beta-tubulin

c) The rate of ATP hydrolysis relative to the rate of ATP-bound tubulin addition

d) The presence or absence of gamma tubulin

66. Telomerase activity was monitored in the following cell types. Which one of the following combination of cell types, an highest activity is recorded

a) Embryonic and hematopoitic stem cells

b) Nerve cells and muscle cells

d) Hepatocytes and eosinophiles

67. Which of the following statements is true about the intermediate filaments

a) Instead of a single kind of protein, they may be made up of different kind of protein

b) They are involved in cell movement

c) Their basic structure is a globular head and long alpha helical tail

d) Like microfilaments, they exhibit treadmilling

68. Actin filaments are involved in the all the following except

c) Contraction smooth muscles

d) Flagellar movement of bacteria

69. Valinomycin, is a cyclic peptide

Q. Facilitates the transport of K+

R. Acts as carrier for K+ transport

S. Facilitate passive transport of cation

70. Diffusion across the plasma membrane is more rapid if a substance is

c) High in its oil: water partition co-efficient

71. RBC glucose transporter specifically transports glucose down its concentration gradient and exhibits hyperbolic saturation kinetics. Thus it is an example of

a) Active mediated transport

b) Passive mediated transport

72. Free fatty acids enter cell by

b) Primary active transport

c) Cannot enter into the cell

d) Secondary active transport

73. The concentration of an electrically neutral substance within a certain type of blood cell is much higher than its is the surrounding blood plasma, yet the substance continues to move into the cell. The process is defined as

74. Tight junctions is best explained by the following statement

a) Are essential components of metabolic coupling

b) Don’t occur in vertebrates

c) Have the closest approach of two plasma membranes of any junction

75. In anchoring junctions, cadherins are linked to

a) Actin filaments in the cell’s cytoskeleton

b) Cell walls of adjacent cells in plants

c) Connexons of its own and adjacent cells

d) Extracellular matrices of adjacent cells

a) Ca2+ dependent transmembrane glycoproteins

b) Responsible for attachment of cell to extra cellular matrix

c) Protein responsible for heterophilic interaction

d) Structural component of gap-junction

77. Which one of the following is found only in plants?

78. The enzyme specific to Glyoxalate cycle is

b) Succinate dehydrogenase

c) Isocitrate dehydrogenase

79. In mammalian cells, beta oxidation occurs in

c) Mitochondria, peroxisome and glyoxisomes

80. In peroxisomes, during oxidation of fatty acids electrons and protons transferred to FAD and NAD. Reduced FAD finally transfer the electrons and protons to O2 and forms

a) Lysosomes - acid phosphotase

c) Mitochondria – cytochrome oxidase

d) SER – amino acid permease

82. All of the following processes occur in the mitochondria of mammalian cells except

a) Fatty acid biosynthesis

d) Beta oxidation of fatty acids

83. The endosymbiotic origin of plastids from bacteria suggested by all the following points except

a) Antibiotic sensitivity of plastid ribosomes

b) Circular DNA in plastids

c) Introns in plastid DNA genes

d) Ribosome size in plastids

84. Proteins made in the cytoplasm and then transported to the chloroplast are

a) Smaller upon initial translation then the final product

b) Made on cytoplasmic free ribosome and not on the ER

c) Possessed hydrophobic signal cleaved at the chloroplast surface

d) Found to contain a general organelle signal rather than one for the plastid

85. In the presence of light, pH of the thylakoid lumen will

86. Plane of formation of cell plate is plant cell is governed by

87. Which statement about the microtubules is false

a) They form the spindle fibers involved in movement of chromosomes during mitosis and meiosis

b) They are involved in cell support and shape

c) They are involved in the movement of flagella

d) They are involved in the cyclosis

88. The proteins that is responsible for the sliding of outer microtubule doublets against one another to produce ciliary bending is

89. Ciliary motion are generated by the sliding action between

a) Adjacent outer doublet microtubules

b) Central pairs of microtubule and outer doublet microtubules

c) Kinesin and outer doublet microtubules

d) Dynein and central microtubules

90. Tay-Sachs disease rarely expressed in population, but common in Ashkenazi Jews of eastern European ancestry, who carries the gene which is expressed under homozygous condition, the disease leads to skeletal, cardiac and respiratory dysfunction resulting in accumulation of a specific glycolipid (ganglioside-GM2), this disease develops due to

a) Defective ER and it lacks enzyme oligosaccharyl transferase

b) Defective lysosomes that lacks enzyme beta-N-acetylhexosaminidase A

c) Defective lysosome that lacks enzyme N-acetylglucosamine phosphotransferase

91. Peroxisome is an organelle always found associated with the following organelle

92. Which one is NOT an extracellular matrix protein

93. Cylindrical channels in gap junctions are made up of

94. When a membrane is depolarized to a voltage value more positive then the threshold voltage, it leads to generation of

d) Electrochemical potential

95. Using FRAP (Fluorescence Recovery After Photo-bleaching) techniques, diffusion coefficient

of three integral membranes proteins M1 M2 and M3, in a kidney cell is calculated as 1um/s, 0.05 um/s and 0.005 um/s, receptively. Considering fluid-mosaic nature of biological membrane and relationship of structural organization of integral membrane protein with diffusion coefficient, which protein(s) will have highest number of integral membrane domain?

96. One highly pathogenic DNA virus enters into the host cells by endocytosis replicates in the nucleus followed by cell lysis. You have drugs at your disposal that block

P. acidification of vesicles

Q. mitochondrial transport

97. When cells enter mitosis, their existing array of cytoplasmic microtubules has to be rapidly broken down and replaced with the mitotic spindle, which pulls the chromosomes into the daughter cells. The enzyme Katanin is activated during the onset of mitosis and chops microtubules into short pieces. The possible fate of the microtubule fragments created by Katanin will be

98. What is the effect of 2,4 dinitrophenol on mitochondria?

a) Blocks ATP synthesis without inhibiting electron transport by dissipating the proton gradient

b) Blocks electron transport and ATP synthesis by inhibiting ATP-ADP exchange across the inner mitochondrial membrane

c) Blocks electron transport and proton pumping on complexes I, II and III

d) Interacts directly with ATP synthase and inhibits its activity

99. Which of the following is NOT associated with insulin action

a) Increased glucose transport

b) Increased glycogen formation

c) Enhanced lipolysis in adipose tissue

d) Decreased rate of gluconeogenesis

100. Which of the following pairs of subcellular compartments is likely to have same pH and electrolyte composition

b) Cytosol and mitochondrial inter membrane space

d) Mitochondrial matrix and inter membrane space

101. Regarding microtubule assembly and disassembly during cell division, which will be appropriate answer

a) Once formed, kinetochore microtubules depolarize at the plus ends throughout the mitosis

b) Once formed, kinetochore microtubules polarize at the plus ends throughout the mitosis

c) Kinetochore microtubules polymerize at their plus ends upto anaphase, at the point they begins to depolymerize

d) Kinetochore microtubules polymerize at their minus ends upto cytokinesis, at which point they depolymerize

102. The size of red blood cells (RBC) in venous blood is greater" than 'that of arterial blood.

This increased size of red blood, cell in the venous blood is due to

a) the increased permeability of red blood cell (RBC) membrane

b) the decreased osmotic pressure in plasma

c) the increased osmotic pressure in RBC

d) the dissociation of cytoskeletal proteins in RBC

103. An investigator new receptor for a new ligand and wanted to identify the binding partner of the receptor i.e. its co-receptor, the antireceptor antibody is not available, but anti GFP antibody is available. Which one of the following strategies is likely used to identify the co-receptor

a) The GFP-receptor fusion protein-is-expressed in a cell line and analyzed by LC-MS/MS

b) The GFP-receptor fusion protein is expressed in a cell line and the cells positive for GFP.

were sorted out, lysed run on a polyacrylamide gel

c) The GFP-receptor protein is' coated on ELISA plate, followed by ELISA with anti-

d) The receptor is cloned as a fusion protein of GFP and expressed in stimulated cells. The immuno-precipitated complex obtained by anti-GFP antibody was analyzed using LC-MS/MS

104. The principal pathway for transport of lysosomal hydrolases. from the trans Golgi network (pH 6.6) to the late endosomes (pH 6.0) and the recycling of M6P (mannose 6 phosphate) receptors back to the Golgi depends on the pH difference between those two compartments. From what you know about M6P receptor binding and recycling and the pathways for delivery of material to lysosomes, predict what would happen if the pH in late endosomes was raised to 6.6?

a) M6P will bind to hydrolases but will not release the hydrolases in the late endosomes

b) M6P will bind to hydrolases and will release the hydrolases in the late endosomes

c) At higher endosomal pH, the receptor would not release the hydrolase and could not be recycled back to the trans Golgi network

d) M6P will be degraded at higher pH

105. Cells that grow and divide in medium containing radioactive thymidine covalently incorporate thymidine into the DNA during S phase. Consider a simple experiment in which cells are labeled by a brief (30 min) to radioactive thymidine. The medium then replaced with one containing unlabeled thymidine and the cells were allowed to grow and divide for some additional time. At different time points after the replacement of the medium, cells are examined under the microscope. Cells in mitosis are easy to recognize by the condensed chromosomes and the fraction of the mitotic cells that have the radioactive DNA can be estimated by autoradiography and plotted as the function of time after the thymidine labeling as in the figure below

The rise and fall of the curve is because

a) Initial rise in the curve corresponds to cells that were just finishing DNA replication, when the radioactive thymidine was added (S phase)

b) The peak of the cells corresponds to cell in the M phase

c) The rise in curve after 20 min corresponds to cells in apoptotic phase

d) The fall in curve after 10 min indicates the cells existing in M phase

106. Mouse erythroleukemia (MEL) cells are used as an in vitro cell culture model for understanding erythropoiesis, These cells are arrested at the stage of pro-erythroblast due to transformation. These cells could be, induced by heme to differentiate further so as to synthesize hemoglobin. The most probable molecular mechanism for this could be that heme may suppress and/or down regulate an endogenous heme-regulated inhibitor (HRI) kinase, an inhibitor of globin synthesis. This down reguIation in turn promotes differentiation.

To validate this hypothesis which of the following approaches is NOT appropriate?

a) Transfect MEL cells with HRI kinase gene

b) Knock down HRI kinase gene in MEL cells

c) Determine the rate of protein synthesis in situ as a function of differentiation

d) Measure HRI kinase activity as a function of differentiation

107. In cells having G protein coupled receptor, inhibition of protein kinase A by siRNA technology led to diminished transcription of androgen binding protein (ABP) and CREB protein. Addition of cAMP, which is a second messenger, will lead to

a) increased transcription of ABP.

b) increased phosphorylation of CREB protein.

c) no change in-transcription, level.

d) increased GTPase activity of G alpha subunit.

108. Binding of a ligand to a cell-surface receptor activates an intracellular signal transduction

pathway through the sequential activation of four protein kinases. In the human cell line

A, these kinases are held in a signaling complex by a scaffolding protein whereas in

another cell line B, these kinases are freely diffusible. Which one of the following

possibilities do you think is NOT correct?

a) Speed of signal transduction will be higher in cell A.

b) Possible cross-linking with other signal transduction pathways will be lesser in cell A.

c) Possibility of signal amplification will be higher in cell A.

d) Potency of spreading signal through other signaling pathways will be higher in cell B.

109. Individual had dehydrated gastrointestinal tract. When an advanced investigation was

done, the person was found to have defects in the following:

P. cystic fibrosis transmembrane conductance regulator protein

Q. glucose transporter protein.

Which of the above could be the cause for such a digestive disorder?

110. The action potential was recorded intracellularly from a squid giant axon bathed in two types of fluid such as sea water and artificial sea water having lower concentration of sodium ions while maintaining the same osmotic pressure with choline chloride. The nature of action potential was different in the two bathing fluids. Which of the following results is most likely?

a) The resting transmembrane potential was not changed but the amplitude of action potential

was increased with lower sodium concentration in the bathing fluid.

b) The amplitude of action potential was gradually decreased with reduction of sodium

concentration in bathing fluid but the duration of action potential was prolonged

c) The resting transmembrane potential was decreased and the amplitude of action

potential was also decreased with lower sodium concentration in the bathing fluid.

d) The amplitude of action potential was not changed with reduction of sodium

concentration in the bathing fluid but the duration of action potential was prolonged

111. Acetylcholine receptor is an archetype for:

a) Ligand-gated ion channel

b) ATPase dependent voltage-gated ion channel

c) ATPase dependent Ca2+-gated ion channel

d) ATPase independent voltage gated ion channel

112. Presence of the nuclear localization signal(NLS) in a steroid receptor indicates that the

a) on the nuclear membrane.

113. Which of the following is an intracellular anchor protein?

114. A nerve fibre cannot be stimulated during the absolute refractory period of a previous

a) sodium permeability remains high

b) sodium-potassium pump does not operate.

c) voltage-gated calcium channels remain closed.

d) potassium conductance remains low.

115. Blood group type A antigen is a complex oligosaccharide which differs from H antigen

present In type O individual by the presence of terminal

116. Phosphatidyl serine (PS) is mostly located in the inner bilayer of plasma membrane of red blood cells (RBCs). You have to prove this fact about PS by an experiment. You are provided with PS specific lytic enzymes (PSE) and other reagents needed. Identify the correct sequence of experiments to be carried out to settle this issue

a) RBCs - inside out vesicles-PSE --Thin Layer Chromatography (TLC)

b) RBCs --right side out vesicles --TLC --PSE

c) RBCs --PSE -- Inside out vesicles --TLC

d) RBCs -- PSE -- TLC -- Inside out vesicles

117. ATP-driven pumps hydrolyze ATP to ADP and phosphate and use the energy released to pump ions or solutes across a membrane. There are many classes of these pumps and representatives of each are found in all prokaryotic and eukaryotic cells. Which of the following statements about these pumps is NOT correct?

a) P-type pumps are multipass transmembrane proteins which phosphorylate themselves

during pumping and involve in ion transport

b) F-type pumps normally use the If' gradient across the membrane to drive the

c) V-type pumps normally use voltage gradient for transport of small molecules

d) ABC transporters primarily pump small molecules across cell membrane.

118. In a given experiment the cells were labeled for 30 minutes with radioactive thymidine. The

medium was then replaced with that containing unlabelled thymidine and the cells were grown for

additional time. At different time points after replacement of medium the fraction of mitotic cells

were analysed, Based on the results obtained, the below figure was drawn which shows the

percentage of mitotic cells that are labeled as a function of time after brief incubation with

Considering the above experiment, the following statements were made:

P. Cells in the S-phase of the cell cycle during the 30 minute labeling period contain radioactive

Q. It takes about 3 hours before the first labeled mitotic cells appear.

R. The cells enter the second round of mitosis at t30 hours.

S. The total length of the cell cycle is about 27 h with G1 being more than 15 h.

Which of the combinations of the above statements is correct?

119. An experimentalist stimulates a nerve fiber in the middle of an axon and records the following

observations. Which one of the observation is correct?

a) Nerve impulse is travelling in a direction towards cell body

b) Nerve impulse is travelling in a direction towards telodendrons

c) Nerve impulses are travelling in both the directions opposite to each other

d) Nerve impulse is not moving in either direction

120. Integrin binds with………………ECM molecule

121. Find out the WRONGLY matched one

122. Phsophatidyl serine is present in which side of a bacterial membrane

a) Outer leaflet of plasma membrane

b) Inner leaflet of plasma membrane

c) Both leaflets of plasma membrane

d) Generally present in inner leaflets but may be outside under certain conditions

123. As compared to intact mitochondria, why the microsome obtained from inner membrane of mitochondria is preferred to investigate mechanism for electron transport chain and ATP synthesis?

a) Difficult to purify mitochondria

b) Easy to study individual enzyme of inner membrane

c) Intact mitochondria do not survive outside cell

d) It is easy to maintain the different concentration of NAD, FAD and ADP with isolated microsomes

124. Cystic fibrosis is caused by a mutation in the gene CFTR transporter protein for chlorine. To test this both wild type and mutated type CFRT proteins were embedded in membrane of liposome in absence of protease or denaturants. It was observed that neither wild type nor mutant transporter on liposome were able to uptake chlorine from surrounding. The possible reason is

a) Wild type CFTR protein got mutated

b) CFTR inserted in invert topology in membrane of liposome

c) CFTR lost affinity for chlorine

d) CFTR lost its functional conformation

125. The drug Ovabain inhibit Na + -K + pump, which blocks the uptake of glucose by epithelial cells of intestine. Which statement represent CORRECT mode of action of ovabain?

a) blocks Na+ transport from intestinal lumen to epithelial cells

b) blocks Na+ transport from intestinal lumen to intestinal cells

c) blocks Na+ transport from intestinal cell to intestinal lumen

d) blocks Na+ transport from epithelial cells to intestinal lumen

126. The receptor mediated endocytosis of pathogen carried out by macrophage, in which receptor interacts with LPS of Leishmania finally endosomal vesicle is formed. TLR-2 is responsible for recognizing LPS and help in phagocytosis and final processing in phagolysosome. Some possible treatments are

P. Treatment with drug methyl β cyclodextrin

Q. Treatment with ammonium chloride as to raise pH of lysosome

R. Treatment with anti-TLR-2 antibody

Which of the following treatment will have lowest count of Leishmania in macrophage?

a) Found only in eukaryotes

b) Non-specific for molecule to be transported

c) Have both transmembrane domain and nucleotide-binding domain

128. Which of the following properties is common to all cytoskeletal motor proteins (including kinesins, dyneins and myosins)

b) Two globular head domains

c) The ability to bind to biological membranes

129. In ATP synthase F0 acts as

130. The DNA molecules within mitochondria and chloroplasts have

b) Covalently closed circular form

c) DNA having covalently sealed end

d) Linear dsDNA with single chain breaks

131. C-bands are deeply stained chromosomal regions which represents the

b) Constitutive heterochromatin

c) Cytosine dominant region of chromosome

1. DNA found at the ends of linear eukaryotic chromosomes

2. protein structure on eukaryotic chromosomes where spindle fibers attach

3. DNA site where kinetochore are found

4. DNA sequence that serves as the template for the synthesis and amplification of ribosomal DNA

133. Which of the following statements is/are false about transport vesicles

P. COPII vesicles transport proteins from the rough ER to golgi

Q. clathrin coated vesicles transport proteins from the trans-golgi to late endosomes

R. COPII vesicles transport proteins between golgi cisternae and from the cis-golgi back to the ER

S. GTPase that acts as a regulatory subunit to control coat assembly for both COPI and clathrin vesicles are ARF

134. Golgi associated vesicles transport

a) ER resident protein back the ER

b) Golgi resident protein in both retrograde and anterograde directions

c) Cargo protein in an anterograde direction

d) All the above statement are correct

135. A mRNA coding for a secretory protein, when translated using free ribosome under in vitro conditions resulted in a 10 kDa protein. The same mRNA when translated using the RER resulted in 36 kDa protein. The different in the molecular weight of the two polypeptides is resulted due to

a) 2 kDa peptode from N-terminus and 2 kDa peptide from the C-terminus

b) 1 kDa peptide from N-terminus and a 3 kDa peptide from the C-terminus

c) 4 kDa peptide from the N-terminus

d) 4 kDA peptide from the C-terminus

136. Proteins are transported around the cell in membranous vesicles. These vesicles

P. form when a section of membrane protrudes and buds off

Q. Have a layer of coat protein around the inside of the vesicles

R. use their transmembrane protein called v-SNARE to find their target membrane

S. Move with the help of motor proteins

137. Docking and fusion of transport vesicles with their target membranes involved

P. each v-SNARE in a vesicular membrane binds to a cognate t-SNARE in the target membrane

Q. SNARE complex is disassembled in an ATP dependent reaction

R. GTP binding protein, the Rab proteins, regulate docking of vesicle with the correct target membrane

S. NSF-catalysed hydrolysis of ATP then drives dissociation of the SNARE complexes

138. The plant vacuoles seems to be large and expanding in any plant cell, which of the following reasons could best explain the situation

a) they are temporary store house of water for plant cells

b) they are evolutionarily oldest organelle, in the primitive cells they accumulated air and

c) They play role in osmoregulation

d) solute accumulation due to action of hydroltic enzyme, facilitating water uptake by

139. If you wish to design a new drug which will act as a inophore to deliver Ca2+ across the nerve cell membrane. This drug would be likely be

a) Hydrophobic on the outside and hydrophilic on the inside

d) Smaller than 0.001 nm in diameter

140. You homogenized plant tissue and would like to separate chloroplasts from nuclei. Which of the following methods would be most suitable?

a) Polyacrylamide gel electrophoresis

b) Differential centrifugation using sucrose gradients

c) Equilibrium density gradient centrifugation on Cs Cl gradients

141. Which one of the following is not a membrane lipid?

142. Lipids that found in biological membranes are

b) Are commonly referred to as triacylglycerols

c) Contain only unsaturated fatty acyl chains

d) Are normally covalently associated with proteins

143. In plasma membrane, carbohydrate present on the

a) Both layer of the lipid

b) Only on cytoplasmic side of lipid bilayer

c) Only on non cytoplasmic side of lipid bilayer

144. Protein which span the lipid bilayer

a) Cannot diffuse in the plane of the membrane

b) Cannot have nay attachment to cytoplasmic components

c) Cannot have bound carbohydrate

d) Usually has both hydrophobic and hydrophilic regions

145. Which of the following are true about proteins that span biological membranes?

P. proteins that span biological membranes often contain alpha helices

Q. The amino acids would be hydrophobic in nature

R. An alpha helic is especially suited to cross a membrane because all of the amide hydrogen atoms and carbonyl oxygen atoms of the peptide backbone take part in intrachain hydrogen bond formation, thus stabilizing these polar atoms in hydrophobic environment

146. Proteins that are embedded in or reach across a membrane are characterized by

P. a stretch of at least 16-21 hydrophobic amino acids in their primary structure

Q. a high lysine, arginine and histidine content

R. a high glutamate and aspartate content

S. at least one alpha helical or beta sheet domain

147. Carbohydrates present in the plasma membrane

d) Helps in molecular recognition

148. Using Fluorescence Recovery after Photobleaching (FRAP)

P. is typically used to measure the rotational motion of membrane lipids and proteins

Q. is typically used to measure of lateral diffusion of membrane lipids and proteins

R. Involved fluorescent labeling of cell-surface molecules

S. has demonstrated that lipids diffuse freely over short distances, but generally no over longer

distance, in fibroblast membrane

149. A patch clamp device is used to

a) Measure the strength of an electrochemical gradient

b) Study the properties of individual neurotransmitters

c) Infuse different kinds of ions into an axon

d) Study the properties of individual membrane channel

150. A passive membrane transport protein

a) Will require a direct source of energy for the transport to occur

b) Can only transport a molecule down the concentration gradient

c) Involves a carrier type transport mechanism only

d) Can move a molecule up a gradient if a membrane potential exists

151. A difference between simple diffusion and facilitated transport is that facilitated transport

a) Is concentration dependent

b) Occurs across plasma membrane

c) Required membrane proteins

d) Utilizes a substance moving with its concentration gradient

152. Which of the following is not related to facilitated diffusion

a) Solutes are moved by a change in shape in the carrier protein

c) The process required energy input

153. When an ion or solute is moved against a concentration gradient using enrgy, the process is called

154. Which of the following is a correct statement for Na-K ATPase?

a) It gives out 3 Na ions and takes up 2 K ions

b) It gives out 2 Na ions and take up 3 K ions

c) It gives out 2 Ca ions and take up 2 K ions

d) It gives out 3 Na ions and take up 2 Ca ions

155. Which of the following effects of the steroid digitalis is observed after treatment of congestive heart failure?

a) Decrease in cytosolic sodium levels

b) Inhibition of Na+-K+ ATPase

c) Decrease in the force of heart muscle contraction

d) Stimulation of the plasma membrane ion pump

156. Transport across a membrane is said to be couples when

a) Two molecules are coupled and transported across the membrane in the same direction

b) Membrane transport is couple to an energy source, such as ATP hydrolysis

c) Transport of one ion down its gradient provides the energy to transport of another molecule against its gradient

d) Both the concentration gradient and membrane potential determine the rate of transport across the membrane

157. Which of the following are correct about transport ATPase

E. The different type of ATPases (P, F and V) transport ions only

F. Na+/K+ pump is an example of P type transport ATPase

G. all members of the ABC superfamily contain two cytosolic ATP binding domains

H. F and V type ATPase do not form phosphoprotein intermediates and transport only proteins

158. The process by which a cell secretes macro-molecules by fusing a vesicle to the plasma membrane is called

159. Most protection against viral disease in the body takes place thought he activities of

160. Antiviral drugs are used to

a) Inhibit the replication of viruses within cells

b) Prevent the formation of enzymes within the viral genome

c) inhibit the formation of the viral envelope

d) Stimulate the production of antibodies in the body

161. In order for viruses to replicate in their host cells, all the following must occur except

a) The genome must be released in the host cell cytoplasm

b) ATP must be synthesized within the virus

c) The virus must unite with the correct host cell

d) The host cell must contain ribosome for the synthesis of proteins

162. Which of the following is/are correct about Botulinum toxins?

P. Phage-encoded neurotoxins

Q. Binds to neuroreceptor gangliosides on cholinergic neurons

S. inhibit release of the stimulatory neurotransmitter, acetylcholine

163. Which of the following is/ are example of A-B exotoxins?

164. Match the correct combination of toxin and mode of action

P. pertussis toxin 1. Prevents release of glycine by nerve end

Q. Diptheria toxin 2. Blocks G-protein signal transduction

R. Botulinum toxin 3. Induces fluid loss from intestinal cells

S. tetanus toxin 4. Inhibits protein synthesis in eukaryotes

6. Blocks release of acetylcholine by nerve endings

165. Cytokinesis in animal cells are caused by

a) The sliding movement of a band of microtubules around the circumference of the cell

b) The contraction of a band of action filaments around the circumference of the cell

c) The movement of the mitotic spindle fibers

d) Endocytosis of the plasma membrane around the equator of the cell

166. Which of the following statement about eh actions or targets of the second messengers of the phophoinositide cascade in incorrect?

a) DAG, activates protein kinase C (PKC)

b) Most of the effects of IP3 and DAG are antagonistic

c) DAD increase the affinity of PKC for Ca2+

d) PKC requires Ca2+ for its activity

a) Catalyze the addition of phosphate residues to proteins

b) Catalyze the removal of phosphate residues from proteins

c) Catalyze the addition of glycosylphosphatidylinositol to proteins

d) Are proteins that specifically bind phosphorylated proteins

168. Match each compound in the left column with its characteristic’s from the right column

P. G-proteins 1. Exchanges with GDP on G subunits

Q. Adenylate cyclase 2. Binds epinephrine

R. IP3 3. Is a second messenger arising from PIP2

S. DAG 4. Is a small G protein GTPase

T Ras 5. Transduces hormone stimulus form an activated

Transmembrane receptor to adenylate cyclase

U. beta adrenergic receptor 6. Is activated by G-GTP

7. Activate protein kinase C

8. has inducible tyrosine kinase activity

169. Which of the following is not a commonly observed consequence of binding of a singling molecule to its cell surface receptor

b) Receptor phosphorylation

c) Conformation changes in the receptor

d) Increased synthesis of the receptor

170. Intracellular receptors

a) Usually bind hydrophobic ligands

b) Maybe located either in the cytosol or nucleus in unbound state

c) When bound to their ligand regulate gene transcription

d) All of the above are correct

171. cAMP activates cAMP dependent protein kinase by

a) stimulating its phosphorylation

b) stimulating the dimerization of the kinase subunits

c) increasing its expression by stimulating the release of a translational inhibitor protein bound to its mRNA

d) binding regulatory subunits and inducing their release from the catalytic subunits

172. Which of the following are the second messengers that are produced by the phosphoinositide cascade?

P. phosphotidyl inositol 4,5 bisphosphate (PIP2)

Q. Inositol 1,4, 5 triphosphate (IP3)

173. Protein phosphorylation is part of most pathways of intracellular signal transduction. All of the following statement about phosphorylation are correct except:

a) Phosphorylation can be on a serine or threonine

b) Phosphorylation changes the structure and function of the protein

c) Protein kinase a cascades result in amplification of the signal

d) Tyrosine kinases are always part of the receptor protein

174. The mechanism of signal transduction by steroid hormones differs from amine and peptide hormones because

a) Steroids use small, water soluble second messengers

b) They bind with specific receptor proteins on target cell plasma membranes

c) They bind to cytoplasmic or nuclear receptors and affect gene expression

d) They are secreted from exocrine glands

175. Which of the following is not true about NO?

a) Acts as intracellular signalling molecule as well as neurotransmitter

b) Regulates the vasodilation

c) Synthesized from L-arginine

d) Induces Adenylate cyclase, which catalyzes cAMP formation

176. Tyrosine kinase receptor

P. should be trimerized to be active

Q. play important role in activating signal transduction cascades

R. have phosphate removing active sites in the cytosolic tails

a) Protein domains that bind phosphotyrosine containing peptides

b) The domains are receptor protein-tyrosine kinase that contain the phosphorylated tyrosine

c) Domains that mediate the dimerization of receptor protein-tyrosine kinases

d) The domains on receptor protein-tyrosine kinases that possess the kinase activity

178. Which of the following signal molecule is responsible for quorum sensing?

a) Acyl homoserine lactone

179. CheA, a protein that participates in bacterial chemotaxis

Q. Shows autophosphorylation

R. Transfers phosphoryl groups to conserved aspartate residues in the CheY

180. The water permeability in the epithelial cells of the renal collecting duct of the kidney is due to the aquaporin channels associated with them, this channels were effected due to the activity of the hormone

181. The anion exchange protein (chloride-bicarbonate exchange protein) present in the RBC, helps in the exchange of bicarbonate and chloride across the membrane, which of the following statements is/ are wrong in respect to their property

P. Transports bicarbonate in one direction and the chloride in the opposite direction

Q. Also involved in the leakage of cations

R. its activity is mediated indirectly by the activity of carbonic anhydrase enzyme

S. It is least abundant protein on the RBC cells

182. Calculate the resting potential for sodium if the concentration inside the cell = 12 mEq/l and the concentration outside the cell = 140 mEq/l.

183. Correctly match the list of neurotoxins and their mechanism of action

Name of the toxin Mechanism of action

P. Tetrodotoxin 1. Binds K channel and blocks ions movement

Q. Dendrotoxin 2. Binds the Na channel and blocks ions movement

R. Batrachotoxin 3. Prevent voltage gated Na channel from opening

S. Sasitoxin 4. Makes Na channel permanently open

184. An action potential in a nerve

a) is terminated by influx of Na+ excessive receptors

b) is terminated by efflux of K+

c) is initiated by efflux of Na+

d) is initiated by influx of K +

185. Which of the following is wrongly matched

a) Microfilaments: actin and myosin

b) Intermediate filaments: Vimentin and keratin

d) Cytoskeleton: Spectin and ankyrin

186. Which intercellular junction directly allow the passage of small molecules and ions between the cytosol of one cell with its neighboring cell, without movement into interstitial fluid

187. The ATPase activity of which of the following proteins is altered to regulate skeletal muscle contraction

188. The major functions/features of the golgi apparatus in eukaryotic cells are

a) It carries out glycosylation of the protein being transported

b) It is the major protein sorting centre of the cell

c) It forms secretory vesicle in tits trans compartment

189. A distinctive features of the lysosome is that it has

a) Lower pH than the cytoplasm

b) A reduced hydrolase activity

190. A marker for an enzyme to go from the golgi to the lysosome is

191. On an active ribosome, the polypeptide chain is synthesized from

c) In variable direction depending on protein

d) From the 5’ end to 3’ end

192. Which of the following is the correct statement?

1. Free ribosome and membrane bound ribosomes are identifical

2. S-S bond formation occurs in the ER lumen

3. When cells are disrupted by homogenization, the endoplasmic reticulum is fragmented into many small closed vesicles called microsome

193. Which of the following is not a property of the mammalian signal recognition particle

a) It targets nascent secretory polypeptides to the rough endoplasmic reticulum

b) It temporarily arrest translation

c) It contains both RNA and peptides

d) It contains a single peptidase activity

194. Which of the following vesicles does not have a clathrin coat when it was first formed?

a) Transport vesicles that form from the endoplasmic reticulum

b) Vesicles formed form coated pits on the plasma membrane

c) Transport vesicles that takes lysosomal enzymes from the trans-golgi reticulum

d) Vesicles that take lysosomal enzyme to the sorting vesicle (late endosomes)

195. Which of the following statement about myosin is not true?

a) Myosin binds to polymerized actin

b) In vitro, myosin assembles spontaneously into the thin filaments

d) Myosin has domain that interact with one another to effect its physiological functions

196. In muscle contraction, what starts filament sliding

a) An increase in Ca 2+ concentration in the cytosol

b) A decrease in Na + concentration in the cytosol

c) The bending of the myosin head

d) The release of energy form the breakdown of ATP

197. What would happen if ATP were suddenly unavailable after the sarcomere had begun to shorten

a) Contraction would proceed normally

b) The myosin heads would unable to detach from action

c) Troponin would bind with the myosin heads

d) Actin and myosin filaments would separate completely and be unable to recombine

198. When the length of a skeletal muscle decreases during an active contraction

a) The A band remains the same size’

b) The H band becomes larger

c) Only can bind to sites on actin molecules

199. Which of the following statement relating to microtubules is not correct

a) The plus end of microtubule is the fast growing end

b) Additionof short fragments of microtubules enhances polymerization

c) A microtubule with GDP-cap enters the shrinkage phase (catastrophe)

d) Critical concentration for polymerization is same for both plus and minus end

200. Which of the following statement is true for skeletal muscle?

P. actin molecules are located in the thick filaments

Q. acetylcholine receptors are located on the surface of the sarcoplasmic reticulum

R. the heads of the myosin molecules attach onto the Z line

S. calcium ion binds to the tropoin molecule

201. Treadmilling of actin filaments refers to

a) Net assembly at both plus and minus ends

b) Net assembly at plus-end and net disassembly at minus-end

c) Net disassembly at plus-end and net assembly at minus-end

d) Net disassembly at both plus and minus end

202. The action potential of skeletal muscle

a) Has a prolonged plateau phase

b) Spreads inward to all parts of the muscle via the T tubules

c) Causes the immediate uptake of Ca2+ into the lateral sacs of the sarcoplasmic reticulum

d) Is longer than the action potential of cardiac muscle

203. The function of Tropomyosin in skeletal muscle include

a) Sliding on action to produce shortening

b) Releasing Ca2+ after initiation of contraction

c) Binding to myosin during contraction

d) Acting as a relaxing protein at rest by covering up the sites where myosin binds to actin

204. Order the following events observed during muscle contraction the correct sequence

8. Calcium is released from the sarcoplasmic reticulum

205. Microtubule are not involved directly in which of the following processes?

a) Motion of whole cells via flagella

b) Movement of mitotic spindle

d) Maintains reticular architecture of the ER

206. Which of the following statement is/are correct

P. The kinetochore is a specialized attachment site for microtubules located at the chromosome centromere it binds to the plus end of the microtubules

Q. A GDP cap at the end of a microtubule will cause it to depolymerize

R. The plus end of Flagellar microtubules point toward the basal body

S. Kinesin moves proteins from the minus to the plus end of microtubules

207. Microtubules associated proteins (MAPs ) are

a) Abundant only in mitochondria

b) Aggregated by colchicine

c) Involved in tubulin polymerization

d) Sensitive to cytochalasin B

208. Colchicine treated cells are arrested in

209. Colchicine is an inhibitory chemical, which

a) Prevents microtubule polymerization

b) Prevents microtubule Depolymerization

c) Stops the functioning of centriole

d) Prevents attachment of spindle fiber with kinetochore

210. The core of cilium, which is composed of entirely of microtubule and their associated protein

211. During the movement of an axoneme

a) The central pair of microtubules slide relative to each other

b) The outer ring of 9 microtubule pairs rotates around the central pair

c) Movement is created by the dynamic instability of the microtubules

d) Hydrolysis of ATP by dynein causes outer microtubules to slide

212. Which of the following statement is correct?

P. Flagella having 9+2 arrangement of microtubules

Q. Centriole having 9+0 arrangement of microtubule

R. Structure of Kinetosome and centriole is same

213. A cellular function, which is inhibited by colchicine and cytochalasin B together, but not separately, probably involves

a) Both microtubule and microfilaments

d) No component of the cytoskeleton

214. Which of the following is not a characteristic of intermediate filaments?

a) They form the nuclear lamina

b) They provide mechanical stability to animal cells

c) Their protein composition is tissue specific

d) They are composed of globular monomers that polymerize to form fibers

215. What property of biomembranes is responsible for their self-sealing nature?


Types of focal epilepsy

An EZ was successfully identified in 36 (85.7%) patients (18 females and 18 males). No EZ was found in the remaining 6 (14.3%) male patients who were diagnosed with idiopathic focal epilepsy (IFE). The types of epilepsy diagnosed base on the comprehensive evaluation are presented in Table 1. The focal epilepsy types diagnosed were divided into MTLE and neocortical epilepsy. Patients with neocortical epilepsy included 9 malformation of cortical development (MCD), which 4 had a surgery with a pathologic result and 5 showed overt MRI manifestations. The epileptogenic zone was defined at the temporal cortex in the remaining 5 neocortical epilepsy cases, but these subjects declined surgery and had no characteristic appearance on imaging.

Watch the video: 8 Προειδοποιητικά Σημάδια Πως Δεν Γίνεται Σωστή Λειτουργία Της Καρδιάς (January 2022).