B2.1.4

• Biological processes need to happen very fast and as a result would demand high pressures and temperatures to occur without enzymes . These conditions are not possible in living cells .
• For reactions to happen molecules must collide in the correct orientation and with enough energy to react .
• Enzymes are biological catalysts meaning they speed up metabolic reactions without being used up . They do this by helping molecules to collide successfully and lowering the activation energy needed for a reaction to occur .
• Define activation energy

  the minimum energy required to start a reaction
• Enzymes are globular proteins that can have a role in both the structure and function of organisms
• Describe the structural role of enzymes

  the synthesis of polymer based components such as collagen , cellulose and contractile fibres are catalysed by enzymes . These are anabolic reactions .
• Describe the functional role of enzymes

  Enzymes catalyse biological processes such as respiration , energy release in metabolic pathways and digestion
• Define an anabolic reaction

  A reaction which constructs molecules from smaller units and requires energy
• Define a catabolic reaction

  A reaction which breaks down molecules into smaller units , releasing energy
• Define metabolism

  The sum of all the different reactions and reaction pathways happening in a cell or organism