What makes something food?

From my (limited) understanding, animals get energy from food by breaking chemical bonds between molecules.

There's a lot of water here [citation needed], so it seems like natural selection would favor any organism that could live off it. Why, in the history of life on earth, hasn't an organism appeared that eats water?

Same applies to dirt, rocks -- (although maybe lichen eat rocks? I'm fuzzy on lichen.)

Or air?

Why are humans and other animals like us only equipped to eat certain types of molecules, when others are so much more plentiful?

You don't get energy from breaking chemical bonds, you only get energy from making chemical bonds, while breaking chemical bonds requires the input of energy. However, in practice chemical bonds are always broken as others are formed, and the net number of bonds is generally constant. Otherwise you would end up with free radicals, which are highly reactive and looking to form a chemical bond with the next thing it touches.

For example, the burning of glucose in respiration involves the breaking of C-C, C-H, C-O and O-H bonds in glucose and O=O bonds in oxygen, with the simultaneous formation of C=O bonds in CO2 and O-H bonds in water. But the C=O bonds in CO2 and O-H bonds in water contain much less energy than the bonds we break within in glucose. So the key is that the bonds formed contain less energy than the bonds broken, and energy is released overall.

And actually it's a bit more complicated than that, because you also have to consider entropy, which is how disordered the system is. Generally the more molecules in a system, the more entropy, so breaking a few big molecules down into lots of small molecules tends to release energy by increasing entropy.

So to answer your question, "food" is what we can draw useful energy from in the process of turning it into something else as we make and break chemical bonds. We can't do this with water, or indeed with rocks, because their chemical bonds would require more energy to break than the energy we'd get back out by forming alternative bonds with anything else.

Plants use both water and air as food using photosynthesis where water is split and recombined with carbon dioxide from air to make glucose.

Overall, the chemical reaction of photosynthesis is as follows:

Light energy + plant enzymes 6CO2 + 12H2O ------------------------------------------------> C6H12O6 + 6O2 + 6H2O

… which means that it takes

six molecules of carbon dioxide plus 12 molecules of water

in the presence of light and the proper enzymes in the cell, to make

one molecule of glucose 6 molecules of oxygen 6 molecules of water

Energy is released when glucose is burnt

about 16 enzymatic rxns C6H12O6 + 6O2 + 6H2O ------------------------------------> 6CO2 + 12H2O + ENERGY

… which means that

one molecule of glucose in the presence of six molecules of oxygen and six molecules of water

can be "burned" to release stored energy as well as the "waste" products of

6 molecules of carbon dioxide and 12 molecules of water

What is Food Science?

Food Science is a convenient name used to describe the application of scientific principles to create and maintain a wholesome food supply.

“Just as society has evolved over time, our food system as also evolved over centuries into a global system of immense size and complexity. The commitment of food science and technology professionals to advancing the science of food, ensuring a safe and abundant food supply, and contributing to healthier people everywhere is integral to that evolution. Food scientists and technologists are versatile, interdisciplinary, and collaborative practitioners in a profession at the crossroads of scientific and technological developments. As the food system has drastically changed, from one centered around family food production on individual farms and food preservation to the modern system of today, most people are not connected to their food nor are they familiar with agricultural production and food manufacturing designed for better food safety and quality.”

“Feeding the World Today and Tomorrow: The Importance of Food Science and Technology” John D. Foloros, Rosetta Newsome, William Fisher from Comprehensive Reviews in Food Science and Food Safety 2010

Food Science has given us

  • frozen foods
  • canned foods
  • microwave meals
  • milk which keeps
  • snacks
  • nutritious new foods
  • more easily prepared traditional foods
  • above all, VARIETY in our diets.

The Food Scientist helps supply this bounty by learning to apply a wide range of scientific knowledge to maintain a high quality, abundant food supply. Food Science allows us to make the best use of our food resources and minimize waste.

Most food materials are of biological origin. How they behave in harvesting, processing, distribution, storage and preparation is a complex problem. Full awareness of all important aspects of the problem requires broad-based training.

To be a Food Scientist and help handle the world's food supply to maximum advantage, you need some familiarity with

  • Chemistry
  • Microbiology
  • Biochemistry
  • Engineering
  • Some specialized Statistics.

With this special training in the applied Food Science, many exciting and productive careers with a wide range of employment opportunities exist for the trained professional, such as

  • Product Development Specialist
  • Sensory Scientist
  • Quality Control Specialist
  • Technical Sales Representative

UC Davis Department of Food Science and Technology Mission Statement

The mission of the department is to generate knowledge about foods through research, and to apply and disseminate knowledge through teaching and outreach, with the goal of ensuring the availability of safe, nutritious, appealing food, with minimum environmental impact, for the benefit of all people.

UC Davis Department of Food Science and Technology
1136 Robert Mondavi Institute North Building
595 Hilgard Lane
Davis, CA 95616

Why does food get stale over time?

James BeMiller, emeritus professor of food science at Purdue University, answers:

When we think of food going stale, we typically think of products such as bread. You might think that bread starts to stale days after it is made. But the process of staling actually begins as soon as the loaf leaves the oven and begins to cool. How quickly bread goes stale depends on what ingredients are in it, how it was baked, and the storage conditions.

Breads are essentially networks of wheat flour protein (gluten) molecules and starch molecules. Suspended inside this scaffolding are pockets of carbon dioxide gas that are produced during fermentation by yeast. This creates a foamlike texture.

The most important event in the process of staling is when starch molecules crystallize. The starch molecules need water molecules to form their crystal structure. They get the water molecules from the gluten. As a result, the network changes, becoming rigid at room temperature and below. This state, however, is reversed with the introduction of heat stale bread can be freshened by warming it&mdashas in toasting.

Function of Food Vacuole

Food vacuoles are membrane-bound sacs within a cell, which contain food matter to be digested. These can be thought of as intracellular “stomachs,” where food is stored while it is broken down and its nutrients are extracted.

To begin the cellular “eating” process, the cell membrane curves to envelope a particle of food. When the cell membrane has enveloped the food completely, it “pinches off,” moving the food fully inside the cell.

The membrane surrounding the food particle is now a “vacuole” – a large membrane-bound sac within the cell.

Once the food vacuole has been created inside the cell, the cell begins to digest it, using a lysosome.

Lysosomes are special membrane-bound sacs inside of cells that contain the cellular equivalent of stomach acid. Just like our stomachs, they contain acid and enzymes to break down nutrients into usable forms.

When a cell wants to digest the food inside a vacuole, the vacuole merges with lysosomes. As the two membrane-bound sacs merge, the contents of the lysosome spill into the food vacuole – and begin digesting the food within.

Over time, the food is converted into usable nutrients for the cell such as sugars, amino acids, and lipids.

Any materials that aren’t usable to the cell are eventually expelled when the vacuole merges again with the cell membrane.

1. Why are there two definitions of “food vacuole?”
A. Because organisms use vacuoles for many different purposes.
B. Because many organisms store food in vacuoles, but there are some differences in how these vacuoles function.
C. Because “food” and “vacuole” are both commonly used terms in biology.
D. None of the above.

However, the term was first applied to the process of digestion used by protozoans, and that is still the dictionary definition of this term.

Answers A. and C. are also true, but B. is the most specific answer to this question.

What are phytoplankton?

Phytoplankton is the base of several aquatic food webs. In a balanced ecosystem, they provide food for a wide range of sea creatures.

Phytoplankton, also known as microalgae, are similar to terrestrial plants in that they contain chlorophyll and require sunlight in order to live and grow. Most phytoplankton are buoyant and float in the upper part of the ocean, where sunlight penetrates the water. Phytoplankton also require inorganic nutrients such as nitrates, phosphates, and sulfur which they convert into proteins, fats, and carbohydrates.

The two main classes of phytoplankton are dinoflagellates and diatoms. Dinoflagellates use a whip-like tail, or flagella, to move through the water and their bodies are covered with complex shells. Diatoms also have shells, but they are made of a different substance and their structure is rigid and made of interlocking parts. Diatoms do not rely on flagella to move through the water and instead rely on ocean currents to travel through the water.

In a balanced ecosystem, phytoplankton provide food for a wide range of sea creatures including shrimp, snails, and jellyfish. When too many nutrients are available, phytoplankton may grow out of control and form harmful algal blooms (HABs). These blooms can produce extremely toxic compounds that have harmful effects on fish, shellfish, mammals, birds, and even people.

The National Centers for Coastal Ocean Science conduct extensive research on harmful algal blooms. Scientists use a range of technologies to predict where and when HABs are likely to form and how they will affect the areas where they occur. Scientists use this information to inform coastal authorities on how to best respond in order to minimize negative impacts.


Birds come in a huge range of colours. These colours can be useful to a bird in two ways. Camouflage colours help to hide the bird, and bright colours identify the bird to others of the same species. Often the male is brightly coloured while the female is camouflaged.

Bird camouflage

Many birds are brown, green or grey. These colours make a bird harder to see: they camouflage the bird. [8] Brown is the most common colour. Brown birds include: sparrows, emus, thrushes, larks, eagles and falcons and the female birds of many species such as: wrens, ducks, blackbirds and peafowls. When a brown bird is in long grass or among tree trunks or rocks, it is camouflaged. [9] Birds that live in long grass often have brown feathers streaked with black which looks like shadows. A bittern is almost invisible in long reeds because its camouflage is helped by its posture (beak and head pointed upwards). Other birds, including starlings and minahs, are quite dark in colour, but are flecked with little spots that look like raindrops on leaves. Bird may also camouflage their nests.

Many birds from hot countries are green or have some green feathers, particularly parrots. Birds that live in green trees often have green backs, even if they have bright-coloured breasts. From the back, the birds are camouflaged. This is very useful when sitting on a nest. [10] The bird's bright-coloured breast is hidden. Budgerigars are bred in different colours such as blue, white and mauve, but in the wild, they are nearly all green and yellow. Even though they fly very well, they normally spend a lot of time on the ground, eating grass seeds. Their yellow and black striped back helps to hide them in the shadows made by long dry grass, while their green breasts are a similar colour to the leaves of gum trees.

Grey birds include most pigeons and doves, cranes, storks and herons. Grey birds are often rock-living birds like pigeons or birds that sit on dead tree trunks looking like a broken branch. Water birds like herons often have a pale grey colour which makes it harder for a fish to notice that the bird is standing, looking down for something to catch. Water birds, no matter what colour they are on top, are often white underneath, so that when a fish looks up, the bird looks like part of the sky.

Black birds include crows, ravens and male blackbirds. Some birds that are dark colours spend quite a lot of time on the ground, hopping around in the shadows under bushes. Among these birds are the male blackbird and the satin bowerbird which is not black but very dark blue. Crows and ravens often perch high on bare trees in the winter, where their black shape against the sky looks like the dark bare branches.

Noticeable colours

Many birds are not camouflaged, but stand out with vivid colours. They are usually male birds whose females are dull and camouflaged. The function of the colours is two-fold. [8] First, the colours help them get mates, and second, the colours identify them to other males of the same species. Many birds are territorial, especially in the nesting season. They give out territory sounds and are easily seen. This lets other males know they will defend their territory. It sends out a "look elsewhere" signal to their competitors.

Some birds are famous for their colour and are named for it, such as the bluebird, the azure kingfisher, the golden pheasant, the scarlet macaw, the violet wren and the robin.

Many other birds are very brightly coloured, in countless combinations. Some of the most colourful birds are quite common, like pheasants, peacocks, domestic fowl and parrots. Colourful small birds include blue tits, the gold finches, humming birds, fairy wrens and bee eaters (which are also called rainbow birds). Some birds, like those of the bird of paradise in Papua New Guinea have such beautiful feathers that they have been hunted for them.

The peafowl is the best example of a display of colour to attract a mate. Also the male domestic fowl and junglefowl have long shiny feathers above his tail and also long neck feathers that may be a different colour to his wings and body. There are only a very few types of birds (like the eclectus parrot) where the female is more colourful than the male.

''Pied birds'' are black and white. Black and white birds include magpies, pied geese, pelicans and Australian magpies (which are not really magpies at all). Pied birds often have brightly coloured beaks and legs of yellow or red. The silver pheasant, with its long white tail striped with fine bars of black, has a brightly coloured face.

Most birds can fly. They do this by pushing through the air with their wings. The curved surfaces of the wings cause air currents (wind) which lift the bird. Flapping keeps the air current moving to create lift and also moves the bird forward.

Some birds can glide on air currents without flapping. Many birds use this method when they are about to land. Some birds can also hover and remain in one place. This method is used by birds of prey such as falcons that are looking for something to eat. Seagulls are also good at hovering, particularly if there is a strong breeze. The most expert hovering birds are tiny hummingbirds which can beat their wings both backwards and forwards and can stay quite still in the air while they dip their long beaks into flowers to feed on the sweet nectar.

A flock of tundra swans fly in V-formation.

This osprey at Kennedy Space Centre is hovering.

A wandering albatross can sleep while flying.

The large broad wings of a vulture allow it to soar without flapping.

The soft feathers of an owl allow it to fly quietly.

Some birds, such as the quail, live mainly on the ground.

A cassowary cannot fly but can defend itself.

Penguin's flippers are good for swimming.

Types of flight

Different types of birds have different needs. Their wings are adapted to suit the way they fly.

Large birds of prey, such as eagles, that spend a lot of time soaring on the wind have wings that are large and broad. The main flight feathers are long and wide. They help the eagle to stay on rising air currents without using much energy, while the eagle looks at the ground below, to find the next meal. When the eagle sees some small creature move, it can close its wings and fall from the sky like a missile, opening its great wings again to slow down as it comes to land. The world's largest eagle, the Philippine eagle has a wingspan of about 2 m (6.7 ft) wide.

Birds that live in grassland areas or open forests and feed on fruit, insects and reptiles often spend a lot of time flying short journeys looking for food and water. They have wings that are shaped in a similar way to eagles, but rounder and not as good for soaring. These include many Australian birds like cockatoos.

Birds such as geese that migrate from one country to another fly very long distances. Their wings are big and strong, because the birds are large and they stock up on food for the long flight. Migrating water birds usually form family groups of 12-30 birds. They fly very high, making use of long streams of air that blow from north to south in different seasons. They are very well organised, often flying in a V pattern. The geese at the back do not have to flap so hard they are pulled on by the wind of the ones at the front. Every so often, they change the leader so that the front bird, who does most work and sets the pace, can have a rest. Geese and swans are the highest-flying birds, reaching 8,000 metres or more when on migration. Geese often honk loudly while they are flying. It is thought that they do this to support the leader and help the young ones.

Birds that fly very quickly, such as swifts and swallows, have long narrow pointed wings. These birds need great speed because they eat insects, catching most of them while they are flying. These birds also migrate. They often collect in huge flocks of thousands of birds that move together like a whirling cloud.

Birds that live in bushes and branches have triangular wings that help the bird change direction. Many forest birds are expert at getting up speed by flapping and then gliding steadily among the trees, tilting to avoid things as they go. Members of the kingfisher family are expert at this type of flying.

Birds such as owls that hunt at night have wings with soft rounded feathers so that they do not flap loudly. Birds that are awake at night are called nocturnal birds. Birds that are awake during the day are diurnal.

A wandering albatross and Arctic tern might spend several years without coming to land. They can sleep while gliding and have wings which, when they are stretched right out, look like the wings of a jet plane.


Flocks of birds can be very highly organised in a way that takes care of all the flock members. Studies of small flocking birds like tree sparrows show that they clearly communicate with each other, as sometimes thousands of birds may fly in close formation and spiral patterns without colliding (or flying into each other).

Two common behaviours in flocking birds are guarding and reconnaissance. When a flock of birds is feeding it is common for one bird to perch on a high place to keep guard over the flock. In the same way, when a flock is asleep, often, one bird will remain awake. It is also common for large flocks to send one or two birds ahead of them when they are flying to a new area. The look-out birds can spy the lie of the land to find food, water and good places to perch. [11]

Flightless birds

Some birds do not fly. These include running birds like ostriches and emus and ocean-living birds, the large penguin family.

Ostriches and emus do not need to fly because although they feed and nest on the ground, their great size and their speed is their protection. Some other ground-feeding birds have not been so lucky. Some birds such as the dodo and the kiwi were ground-feeding birds that lived in safety on islands where there was nothing dangerous to eat them. They lost the power of flight. Kiwis are endangered because European settlement to New Zealand brought animals like cats, dogs and rats which kill kiwis and eat their eggs. However, kiwis and also the rare New Zealand ground parrot have survived. In the case of dodos, they were fat and delicious. They were killed and eaten by sailors until there was none left. Other flightless birds which have disappeared are the great auk and the moa.

Penguins spend a great deal of time at sea, where they are in danger from seals. On land, they usually live in areas where there were few dangers, until the arrival of European settlers with dogs and cats. Their wings have adapted to life in the sea and have become flippers which help them in swimming very fast.

Modern birds do not have teeth, and many swallow their prey whole. Nevertheless, they must break up food before it is digested. First of all, along their throat (oesophagus) they have a crop. This stores food items before digestion. That way a bird can eat several items, and then fly off to a quiet spot to digest them.

Their stomach comes next, with two very different parts. One part is like a straight hollow rod which secretes mild hydrochloric acid and an enzyme to break down protein. The other part of the stomach is the gizzard. This is muscular, and grinds up the contents. In herbivorous birds the gizzard contains some gastroliths (small stones or pieces of grit). Bones of fish will mostly be dissolved by the stomach acid. The partly digested and ground-up food now goes to the intestine, where digestion is completed, and most contents are absorbed. Anything indigestible, for example remains of feathers, is regurgitated via the mouth, not the cloaca.

The system is effective, and carnivorous birds can swallow quite large prey. A blue heron can swallow a fish as large as a carp successfully. [12] Raptors eat by holding the prey down with a foot, and tearing it apart with their beak.


Although birds are warm-blooded creatures like mammals, they do not give birth to live young. They lay eggs as reptiles do, but the shell of a bird's egg is hard. The baby bird grows inside the egg, and after a few weeks hatches (breaks out of the egg).

Birds in cold climates usually have a breeding season once a year in the spring. Migratory birds can have two springs and two mating seasons in a year.

When the breeding season arrives, the birds choose partners.

Ninety-five per cent of bird species are socially monogamous. These birds pair for at least the length of the breeding season. In some cases this arrangement lasts until the death of one of the pair. [13] Monogamy helps where females need males' help to raise a brood successfully. [14]

Many birds mate for life, like married couples. These birds include pigeons, geese, and cranes. Other birds look for new partners each year.

For birds that choose new mates, part of the breeding season is display. The male bird will do all sorts of things to attract females. These include singing, dancing, showing off the feathers and building a beautiful nest. Some male birds have splendid feathers for attracting females. The most famous is the peacock who can spread the feathers above his tail into a huge fan.

Biology Food Experiments

We found TONS of super clever and unique biology experiments you can make with food! Whether you make an edible cell, make a candy neuron model, or try growing gummy bear – these science experiments are sure to leave an impression!

    from My Joy-Filled Life. What a delicious hands on way to learn about the life cycle of a butterfly. from Teach Beside Me. Here is another delicious life cycle model. from 123 Homeschool 4 Me. These amazing models are a great way to teach kids about the different structures of the eye and skin. from 123 Homeschool 4 Me. I love this hands on idea for learning about DNA cells. from 123 Homeschool 4 Me. Who knew you could make a human spine out of food! from Farmer’s Daughter. Learn about what is under the ground with this yummy snack. from 123 Homeschool 4 Me. Practice being a geologist and take a core sample from a cupcake! from The Chaos and The Clutter. There are lots of cool jello experiments in this article but my favorite is the enzymes vs protein biochemistry experiment. from Left Brain Craft Brain. Who knew you could learn all about single cell microorganisms (aka yeast) while making bread! from Journey to Excellence. What a clever way to learn about the structure of a cell. from Adventures in Mommydom. This is a simple way to learn about the basic structures of animals cells. from Big Red Kitchen. Learn about blood then drink the experiment! from Connections Academy. This is a great hands on way to learn about the structures of the heart. from All Things Beautiful. Learn about the respiratory system with this edible model. from A School of Fish. This is a yummy way to learn all about neurons.

Challenging Projects

Coin Game Find out whether a simple game is rigged or not! Try to cheat your friends!
Related fields: Mathematics (Game Theory) Conductors, Semiconductors, Insulators, and Superconductors Let's investigate more about the materials that enabled us to have computers and other wonderful electronics.
This is not a full project guide, but provides multiple ideas.
Related fields: Materials Science Galileo's Gravity Experiment Repeat the experiment that Galileo used to measure the acceleration of gravity.
Related fields: Physics (Kinematics) Lights and Sounds of Logic How to implement logic operations using simple circuitry that produces light and sound.
Related fields: Mathematics (Logic)/Physics (Electronics) Measuring Characteristics of Planets You don't need to take a ruler to space to know how far and big planets are!
This is not a full project guide, but provides multiple ideas.
Related fields: Physics (AstroPhysics) Platonic Solids Investigate the five platonic solids.
Related fields: Mathematics (Geometry) Randomization Is it really possible to make something really random?
This is not a full project guide, but provides multiple ideas.
Related fields: Mathematics Tic Tac Toe Analysis Study the game of tic-tac-toe and try to develop an optimal strategy.
Related fields: Mathematics (Game Theory) Winning Strategy Play a simple counting game and develop a winning strategy.
Related fields: Mathematics (Game Theory)

Physicians' Continuing Medical Education Program
Resources for talking to patients about using the Nutrition Facts label to make healthy food choices.

Pediatricians' Continuing Medical Education Program
Resources for talking to parents and patients about using the Nutrition Facts label to make healthy food choices.

The psychology of food cravings

Swimsuit season is almost upon us. For most of us, the countdown has begun to lazy days lounging by the pool and relaxing on the beach. However, for some of us, the focus is not so much on sunglasses and beach balls, but how to quickly shed those final five or ten pounds in order to look good poolside. It is no secret that dieting can be challenging and food cravings can make it even more difficult. Why do we get intense desires to eat certain foods? Although food cravings are a common experience, researchers have only recently begun studying how food cravings emerge.

Psychological scientists Eva Kemps and Marika Tiggemann of Flinders University, Australia, review the latest research on food cravings and how they may be controlled in the current issue of Current Directions in Psychological Science, a journal of the Association for Psychological Science.

We've all experienced hunger (where eating anything will suffice), but what makes food cravings different from hunger is how specific they are. We don't just want to eat something instead, we want barbecue potato chips or cookie dough ice cream. Many of us experience food cravings from time to time, but for certain individuals, these cravings can pose serious health risks. For example, food cravings have been shown to elicit binge-eating episodes, which can lead to obesity and eating disorders. In addition, giving in to food cravings can trigger feelings of guilt and shame.

Where do food cravings come from? Many research studies suggest that mental imagery may be a key component of food cravings -- when people crave a specific food, they have vivid images of that food. Results of one study showed that the strength of participants' cravings was linked to how vividly they imagined the food. Mental imagery (imagining food or anything else) takes up cognitive resources, or brain power. Studies have shown that when subjects are imagining something, they have a hard time completing various cognitive tasks. In one experiment, volunteers who were craving chocolate recalled fewer words and took longer to solve math problems than volunteers who were not craving chocolate. These links between food cravings and mental imagery, along with the findings that mental imagery takes up cognitive resources, may help to explain why food cravings can be so disruptive: As we are imagining a specific food, much of our brain power is focused on that food, and we have a hard time with other tasks.

New research findings suggest that that this relationship may work in the opposite direction as well: It may be possible to use cognitive tasks to reduce food cravings. The results of one experiment revealed that volunteers who had been craving a food reported reduced food cravings after they formed images of common sights (for example, they were asked to imagine the appearance of a rainbow) or smells (they were asked to imagine the smell of eucalyptus). In another experiment, volunteers who were craving a food watched a flickering pattern of black and white dots on a monitor (similar to an untuned television set). After viewing the pattern, they reported a decrease in the vividness of their craved-food images as well as a reduction in their cravings.

According the researchers, these findings indicate that "engaging in a simple visual task seems to hold real promise as a method for curbing food cravings." The authors suggest that "real-world implementations could incorporate the dynamic visual noise display into existing accessible technologies, such as the smart phone and other mobile, hand-held computing devices." They conclude that these experimental approaches may extend beyond food cravings and have implications for reducing cravings of other substances such as drugs and alcohol.

Story Source:

Materials provided by Association for Psychological Science. Note: Content may be edited for style and length.

How our bodies turn food into energy

All parts of the body (muscles, brain, heart, and liver) need energy to work. This energy comes from the food we eat.

Our bodies digest the food we eat by mixing it with fluids (acids and enzymes) in the stomach. When the stomach digests food, the carbohydrate (sugars and starches) in the food breaks down into another type of sugar, called glucose.

The stomach and small intestines absorb the glucose and then release it into the bloodstream. Once in the bloodstream, glucose can be used immediately for energy or stored in our bodies, to be used later.

However, our bodies need insulin in order to use or store glucose for energy. Without insulin, glucose stays in the bloodstream, keeping blood sugar levels high.

How the body makes insulin

Insulin is a hormone made by beta cells in the pancreas. Beta cells are very sensitive to the amount of glucose in the bloodstream. Normally beta cells check the blood's glucose level every few seconds and sense when they need to speed up or slow down the amount of insulin they're making and releasing. When someone eats something high in carbohydrates, like a piece of bread, the glucose level in the blood rises and the beta cells trigger the pancreas to release more insulin into the bloodstream.

Insulin opens cell doors

When insulin is released from the pancreas, it travels through the bloodstream to the body's cells and tells the cell doors to open up to let the glucose in. Once inside, the cells convert glucose into energy to use right then or store it to use later.

As glucose moves from the bloodstream into the cells, blood sugar levels start to drop. The beta cells in the pancreas can tell this is happening, so they slow down the amount of insulin they're making. At the same time, the pancreas slows down the amount of insulin that it's releasing into the bloodstream. When this happens, the amount of glucose going into the cells also slows down.

Balancing insulin and blood sugar for energy

The rise and fall in insulin and blood sugar happens many times during the day and night. The amount of glucose and insulin in our bloodstream depends on when we eat and how much. When the body is working as it should, it can keep blood sugar at a normal level, which is between 70 and 120 milligrams per deciliter. However, even in people without diabetes, blood sugar levels can go up as high as 180 during or right after a meal. Within two hours after eating, blood sugar levels should drop to under 140. After several hours without eating, blood sugar can drop as low as 70.

Using glucose for energy and keeping it balanced with just the right amount of insulin — not too much and not too little — is the way our bodies maintain the energy needed to stay alive, work, play, and function even as we sleep.

Insulin helps our bodies store extra glucose

Insulin helps our cells convert glucose into energy, and it helps our bodies store extra glucose for use later. For example, if you eat a large meal and your body doesn't need that much glucose right away, insulin will help your body store it to convert to energy later.

Insulin does this by turning the extra food into larger packages of glucose called glycogen. Glycogen is stored in the liver and muscles.

Insulin also helps our bodies store fat and protein. Almost all body cells need protein to work and grow. The body needs fat to protect nerves and make several important hormones. Fat can also be used by the body as an energy source.

How diabetes changes the way this works

With diabetes, the body has stopped making insulin, has slowed down the amount of insulin it's making, or is no longer able to use its own insulin very well. When this happens, it can lead to several things.

For example, glucose cannot enter the cells where it's needed, so the amount of glucose in the bloodstream continues to rise. This is called hyperglycemia (high blood sugar).

When blood sugar levels reach 180 or higher, the kidneys try to get rid of the extra sugar through the urine. This makes a person urinate more than usual. It also makes a person feel thirstier because of the water he or she is losing by urinating so much.

When a person loses sugar in the urine, it's the same as losing energy because the sugar isn't available for the cells to use or store. When this happens, a person might feel tired, lose weight, and feel hungry all the time.

Other problems caused by high blood sugar include blurry vision and skin infections or injuries that don't heal. Women might have vaginal yeast infections more often.

When the body doesn't have enough insulin to help convert sugar into energy, it often starts burning body fat instead. This sounds like it might work well, but burning too much fat for energy produces a byproduct called ketones. High levels of ketones can lead to a condition called diabetic ketoacidosis (DKA), which can be life threatening if not treated quickly. DKA is more common in type 1 diabetes because the body has stopped making insulin.

Keep blood sugar levels under control

For a person with diabetes, the main focus of treatment is to control the amount of glucose in the body so that blood sugar levels stay as close to normal as possible.

People with type 1 diabetes need insulin shots as part of their care plan to control their blood sugar levels. Some people with type 2 diabetes can control their blood sugar levels with a healthy diet and exercise. However, many people with type 2 diabetes will need to include diabetes pills, insulin shots, or both in their diabetes care plans.

People with either type 1 or type 2 diabetes need to pay close attention to how blood sugar levels change at various times throughout the day in order to keep them as close to normal as possible. When blood sugar levels are close to normal, it means the body is getting the energy it needs to work, play, heal, and stay healthy.