Amino acid

A condensation reaction

Haemoglobin is a protein.This means that haemoglobin is a polymer and the monomers are amino acids. Every Amino acid has a carboxylic acid group and an amino group. There are 20 different amino acids each having a different R group. Two amino acids are joined together to form a dipeptide. In this reaction two hydrogen atoms and one oxygen Atom are removed. This kind of reaction is called a condensation reaction because water is produced as a waste product. The bond formed is called a peptide bond. many amino acids joined together are a polypeptide.  

The primary structure of a protein is the number and sequence of amino acid in the polypeptide chain. Haemoglobin is a very complex protein. It is made up of four polypeptide chains. Two are identical and are called alpha chains. The other two are also the same as each other and are called beta chains. each chain has over 100 amino acids in it.

The polypeptide chains are so long they can twist or coil to form different shapes. weak bonds called hydrogen bonds form between different peptide bonds in different parts of the chain. The shape a polypeptide chain folds into is called a secondary structure of the protein. Two common kinds of secondary structure are the alpha helix and the beta pleated sheet.. 

The polypeptide chains can fold again to produce a complex three dimensional shape. the overall shape is called the tertiary structure. this is held in place by bonds that form between the R groups of amino acids in the chain. several different kinds of bonds, these include: weak hydrogen bonds, and much stronger bonds called disulfide bonds.

The functional protien is made up of more than one polypeptide chain. The chains are held together by bonds between R groups as in the Tertiary structure.