Enzymes

• Enzymes are biological catalysts
• ‘Biological’ because they function in living systems
• ‘Catalysts’ because they speed up the rate of chemical reactions without being used up or undergoing permanent change
• Enzymes are globular proteins with complex tertiary structures
• Some are formed from a single polypeptide, whilst others are made up of two or more polypeptides and therefore have a quaternary structure
• Intracellular enzymes are produced and function inside the cell
• Extracellular enzymes are secreted by cells and catalyse reactions outside cells