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H — C

NH2

R

COOH

We eat every day, but do you ever pause

to consider what’s actually on your plate? In

general, food is any substance that creatures

scarf down in order to provide their bodies with

nutrition and energy. It comes from two main

sources: plants and animals. Food from plants

takes the form of vegetables, fruits, and seeds,

while we eat the meat, milk, and eggs

of animals.

When we take a closer look at food,

we see that we can break these two groups

down further. Food from plants is usually rich

in carbohydrates, which fuel the body with the

sugar it needs to do its thing! Carbohydrates

are composed of the elements carbon, hydrogen,

and oxygen. Your body easily and quickly

digests simple carbs, such as the fructose and

sucrose found in fruit and candy. Complex carbs,

also called starches, such as bread, crackers,

and pasta, take more time to digest.

Food from animals is commonly rich in

protein. (You can get proteins from the seeds

of plants, too.) This crucial stuff helps your

body build and maintain itself—it’s what your

muscles, organs, bones, skin, and immune

system are all made of. Proteins are strings of

amino acids, molecules of hydrogen, carbon,

oxygen, and nitrogen (plus a bit of sulfur).

There are twenty universal amino acids, but

humans can only make eleven. The other nine

are called essential amino acids since your

body needs to get them from food in order to

keep itself operating in good form.

What Is Food?

Let’s zoom in on mealtime to see

what nutrition is really all about.

Next up are fats. Also called lipids, fats

are made of carbon, hydrogen, and oxygen,

too. But lipid molecules have lots more

hydrogen atoms. Fats stretch out in long

chains, linked by carbon atoms with hydrogen

atoms dangling off each. You may have heard

that fats aren’t good for you, but their bonds

provide energy that your body can use when

it’s low on fuel. We get fats from animals but

also from veggies and nuts.

12

phe

amino group

R group

carboxyl

group

amino acids

Proteins are made up of strings of amino

acids, such as cysteine (cys), serine (ser),

leucine (leu), and phenylalanine (phe),

as shown here.

PRIMARY PROTEIN

STRUCTURE

amino acid

structure

UNSATURATED FAT

leu

ser

cys

The molecular structure of

the simple sugar glucose.