4. What Are Proteins?

We know now why we need protein in our diet, but what actually is protein? If you ask the average person what is the first thing that comes into his mind when you say "protein," he will most likely respond with "meat." Is protein simply meat or eggs or nuts?

Protein is one of the three categories for all foods, the other two being carbohydrates and fats. Proteins are highly complex compounds of carbon, hydrogen, nitrogen, oxygen and small amounts of sulphur or iodine. They are present in the protoplasm of every living cell and are involved in every organic activity of an organism.

4.1 Principal Proteins and Their Chemical Compositions

There are many different types of proteins within the bodies of animals and plants. For example, all plants have at least two different types of protein, and within the human body are over 100,000 different kinds of proteins. Although all of these proteins differ in their molecular structure, they all have approximately the same chemical composition of 53% carbon, 22% oxygen, 17% nitrogen, 7% hydrogen and 1% sulphur, iodine, etc.

The principal vegetable proteins are albumin (found in fruits and vegetables), gluten (in wheat and cereals), legumin (in peas and beans), globulin (in nuts) and mucleo-protein (in peas and beans), globulin (in nuts) and muco-protein (in seeds). Some of the animal proteins are casein (found in milk and dairy products), gelatin (in bones and tendons), fibrin (in blood) and myosin (in the flesh of animals).

All of these proteins are composed of amino acids. An amino acid is simply a substructure of a protein compound. You can think of protein as being chains of amino acids that are linked together to form one structure.

For example, a protein compound known as globulin exists in pumpkin seeds. It is composed of the following elements:

Element	Number of Atoms in the Molecule
Carbon	292
Hydrogen	481
Nitrogen	90
Oxygen	83
Sulphur	2

Within this globulin protein molecule are chains of amino acids that make up the compound.

In the following example, an amino acid called isoleucine is contained within this protein molecule. It is composed of the following elements:

Element	Number of Atoms in the Amino Acid
Carbon	6
Hydrogen	13
Nitrogen	1
Oxygen	2

4.2 Amino Acids Are the Building Blocks

You can see that many amino acids are necessary to form one protein compound. In many cases, several different types of amino acids are in the same protein molecule. It is these amino acids that are important to the body, and this is what the body uses protein for.

When you hear the word "protein" now, you should think of "amino acids."