Enzymes

• Enzymes are large globular proteins with complex 3D shapes, primary to at least tertiary structure (possibly quaternary); they act as biological catalysts (speed up chemical reactions in cells without being used up or changed in the reaction)
• Increase a product’s rate of formation in a biological reaction (up to a million times faster) each enzyme only catalyse one reaction (specificity) as substrate binding occurs at the active site which has a complementary shape to that of the substrate
• The binding of substrate to specific enzyme forms an enzyme-substrate complex (ESC); when the ESC is formed, the groups on the substrates form temporary (e.g. hydrogen) bonds to the R groups of the amino acids which make up the active site
• The active site is small compared to the rest of the enzyme; from 3-12 AA residues; the rest of the enzyme molecule is involved in maintaining the active site
• Products are released from the active site since they are no longer complementary in shape (also charges may have changed) and the enzyme is recycled to catalyse the same reaction with another substrate molecule
• Some enzyme reactions are anabolic, where 2 or more substrates are combined to form a product (ie they build up molecules) and other enzyme reactions are catabolic, where a substrate is broken down to form 2 or more products