Protein

Proteins form a class of nitrogenous (containing nitrogen) compounds that consist of large molecules of chains of amino acids. Proteins are an essential part of all living organisms, esp. structural components of body tissues such as muscles, hair, skin. They also exist in living bodies as enzymes and antibodies. Proteins are needed for cells to grow. Protein in food gives us calories, four calories in one gram.

Our bodies can make most amino acids. A few amino acids we must get from the food we eat. These are known as 'essential amino acids.'