There are twenty main amino acids in proteins, and any one protein may contain several hundred or over a thousand amino acids, so an enormous variety of different proteins occur in nature, i.e. in foods and our bodies.
Proteins are constituents of all living cells and are dietary essentials.
Chemically they are distinguished from fats and carbohydrates by containing nitrogen. They are composed of carbon, hydrogen, oxygen, nitrogen, sulphur, and sometimes phosphorus. A Dictionary of Food and Nutrition 2. enzyme A Dictionary of Food and Nutrition 3. enzyme Oxford Paperback Encyclopedia 4. All rights reserved.