1. Enzyme Quiz 1. What is an enzyme? 2. What is it made from? 3. How does it speed up reactions? 4. What special structure does it have? 5. What is the significance of this structure? 6. What model describes enzyme activity? 7. What factors affect enzyme activity? 8. Name 3 types of enzymes and the reaction they catalyse.

2. Enzymes All enzymes are globular proteins with a tertiary structure They are all catalysts They are specific They have an active site Their activity is affected by pH and temperature

3. Enzymes based reactions regulate metabolic reaction at the cellular level but this can influence the structure and function of the whole organism

4. They may be intracellular or extracellular E.g. catalase is an intracellular enzyme found in hepatocytes (liver cells) that detoxifies hydrogen peroxide to water and oxygen Digestive enzymes such as amylase, pepsin, Trypsin and lipase are secreted into the digestive tract so are extracellular enzymes

5. How do enzymes work? For a reaction to happen, bonds must be broken and new bonds made. The energy required to break the original bonds, so that a reaction can proceed, is called the activation energy. Enzymes speed up reactions by reducing the activation energy. But how do enzymes lower the activation energy needed? Energy is needed to break the original bonds, so that a reaction can occur – activation energy

6. Remember the lock and key hypothesis? Annotate the diagram with your existing knowledge Now compare with the person you are sitting next to and add further annotations in a second colour Finally add any of the following terms that are missing in your explanation: Tertiary structure, specificity, active site, enzyme substrate complex, enzyme product complex, product formed

7. Lock and Key – The original hypothesis

8. Induced Fit – The accepted hypothesis

9. The formation of the enzyme-substrate complex causes conformational changes in the shape of the substrate. This weakens the bonds holding it together. Less (activation) energy is now needed in order to break the bonds and for the reaction to proceed. A product is therefore produced, and it is now referred to as an enzyme-product complex. The products no longer fit into the active site so they move away, allowing the enzyme to be reused. http://highered.mcgraw- hill.com/sites/0072495855/student_view0/chapter2/animation__how_enzymes_wor k.html