enzymes

• enzymes are biological catalysts
• catalyse metabolic reactions at a cellular level (respiration) and for the organism as a whole (digestion in mammals)
• enzymes are proteins
• have an active site which has a specific shape
• the active site of the enzyme is where the substrate molecules (the substance that enzyme interacts with) bind to
• are highly specific due to their tertiary structure
• enzymes lower the activation energy of a reaction
• activation energy for enzymes is often provided as heat
• enzymes lower the activation energy that a chemical reaction needs before it will start making reactions happen at a lower temperature
• enzymes lower the activation energy of a reaction which speeds up the rate of reaction
• when a substrate fits into the enzyme's active site it forms an enzyme-substrate complex which lowers the activation energy
• if two substrate molecules need to be joined, being attached to the enzyme holds them close together reducing any repulsion between the molecules so that they can bond more easily
• if an enzyme is catalysing a breakdown reaction, fitting into the active site puts a strain on the bonds in the substrate, so the substrate molecule breaks up more easily