Proteins contain carbon, hydrogen and oxygen but also nitrogen. Many proteins also contain sulphur and some proteins contain phosphorus.
Proteins are polymers, and they are made up of thousands of repeating monomers called amino acids. There's about 20 different amino acids, therefore there is thousands of combinations that are possible, proteins are very varied molecules. The arrangment of the amino acids in a protein determines it's shape, and this determines its function.
When you join two amino acids together, a dipeptide is formed. Polypeptides are formed when more than two amino acids joined together. The type of bond that joins amino acids together is called a peptide bond, it is a covalent bond. The monomers join together in a condensation reaction, the end result is more condensed that the component parts and also water is producde as a by-product.
When amino acids join together they line up in a linear sequence, the amino groups of one amino acids reacts with the carboxyl group of another amino acid, producing water. When a polypeptide folds up into a 3D structure a protein is made. You can recognize a polypeptide as it has the backbone NCCNCCNCC...
Amino acid structure
All amino acids have the same general structure:
- They have an amino group (NH2) which is basic (alkaline)
- They have a carboxyl group (COOH) which is acidic
- They have an R group which differs…