- Proteins differ from carbohydrates and lipids in that in addition to carbon, hydrogen and oxygen, they contain nitrogen. Many proteins also contain sulphur and sometimes phosphorous.
- Proteins are large compounds builts up of sub-units called amino acids. About 20 different amino acids are used to make up proteins. There are thousands of different proteins and their shape is determined by the specific sequence of amino acids in the chain.
- All amino acids have the same basic structure in that each possesses an amino group, -NH2, at one end of the molecule, and a carboxyl group, -COOH, at the other end. However, each amino acid has a different R group
Formation of a peptide bond
Proteins are built up from a linear sequence of amino acids. The amino group of one amino acid reacts with the carboxyl group of another with the elimination of water. The bond that is formed is called a peptide bond and the resulting compound is a dipeptide.
Proteins are very large molecules and consist of long chain of many amino acids joined together. These chains are called polypeptides.
This is the sequence of amino acids in a polypeptide chain. As polypeptides have many of the 20 amino acids joined in any sequence, there…