What are proteins?
In a strand of your hair, in the lens of your eye or in a cell of a leaf — wherever you look, you will find proteins. There is no living cell without protein. It is a component that every cell simply cannot do without.
The main chemical difference between carbohydrates and proteins comes down to one element.
The elements in a protein molecule
In every protein: Carbon (C) · Hydrogen (H) · Oxygen (O) · Nitrogen (N)
Only in some proteins: Sulphur (S)
Telling proteins apart
Nitrogen, which is not found in carbohydrates at all, is always found in proteins. The tests used to identify proteins are also based on this nitrogen.
About 17% of the human body is made of protein material
About 17% of an adult human body is made up of protein material. In a person weighing 60 kilograms, about 10 kilograms is protein. By mass, protein is second only to water in the body.
A protein is a chain of molecules
A protein molecule is a long, complex chain made when a great many small, simple molecules called amino acids join together. This is not a new idea for you — do you remember how, in polysaccharides, a small unit joined again and again to make a large molecule? The only difference with proteins is that the unit is an amino acid instead of glucose.
Protein-rich foods
- Meat
- Fish
- Egg white
- Pulses such as dhal (lentils), mung bean and cowpea
- Milk and milk products