Protein structure

Primary

Primary

Refers to the sequence or of amino acids in the polypeptide chains. These amino acids are linked together by peptide links, primary structure also refers to the number of amino acids in each polypeptide chain

Secondary

Involves further linking of amino acids in the polypeptide chain(s) to give the protein a definite shape which is often in the form of a spiral, structure is caused by cross links; Disulphide, Hydrogen bonds

Disulphide links

Occurs when two sulphurs join within one polypeptide chain or between two

Hydrogen bonds

Formed when the hydrogen in one amino acids joins with an oxygen of another amino acid, bonds are formed within one polypeptide chain or between two

Tertiary

Pattern of folding of the polypeptide chains to give a three dimensional compressed unit, protein chains cross link forming either a fibrous or a globular protein structure

Fibrous proteins

Polypeptide chains are straight, coiled, zigzag, insoluble in water, not easily denatured e.g. keratin, collagen, gluten

Globular proteins

Polypeptide chains are spherical, soluble in water, easily denatured e.g. ovalbumin, lactalbumin