Protein

Protein the principal material of which animals are made. Proteins also play an important role in the life of plants and other living things; for example, all the enzymes that control chemical reactions in organisms are proteins. Thousands of kinds of protein are known, and more are constantly being discovered.

Proteins are composed of carbon, hydrogen, oxygen, and nitrogen; it is the presence of the last of these which distinguishes proteins from the other materials of life. There is often also a little sulphur and phosphorus. Proteins are highly complex substances with huge molecules containing thousands or millions of atoms. Each molecule is a long chain made up of smaller molecules known as amino acids. These are joined by a link called a ‘peptide bond’, which is fairly weak and easy to break.