The rate of reaction of Succinate dehydrogenase :: GCSE Chemistry Coursework Investigation

The rate of reaction of Succinate dehydrogenase Introduction: Enzymes are protein molecules that function as biological catalysts that can help break larger molecules into smaller molecules while remaining unchanged themselves. They speed up the chemical reactions by lowering the energy of activation barrier, are specific to one molecule. The enzyme’s specificity arises from its active site, an area with a shape corresponding to the molecule with which it reacts (the substrate). The shape of the enzyme where the chemical binds only allows the binding of that particular chemical, or inhibitor substrates that are structually similar to the substrate, competing for the active site. The enzyme and the substrate slot together (like a key for a lock, or by induced fit) forming an enzyme–substrate complex that allows the reaction to take place. An enzymes activity is affected by its environment. Each enzyme has a temperature and pH level at which its activity is greatest and the reaction it catalyses proceeds at its fastest rate. The rate of enzyme-catalysed reactions increases as the temperature and pH balances approach its optimum level. At higher or lower temperatures and pH balances, the enzyme molecules become damaged or 'denatured'. They cannot catalyse the reaction very well, if at all, and the damage is usually permanent (Campbell, et al, 2006). The aim of this study was to investigate the rate of reaction of succinate dehydrogenase, an enzyme extracted from chicken hearts. The rate of reaction was analysed considering two factors: pH and temperature. The ability for the enzyme succinate dehydrogenase to oxidise two alternative substrates (malonate and propionate) will also be examined. Materials and Method Part 1. Effect of pH on enzyme activity Blender 50 grams of fresh chicken hearts - 2 days old purchased from local butcher: Rays meats Sorrento. Chicken hearts were kept in fridge until prepared the evening of purchase. 3 test tubes Distilled water 0.2M Na2HPO4 with 100ml distilled water (solution 1) 0.2M NaH2PO4 with 100ml distilled water (solution 2) 0.1M succinate with 100ml distilled water 0.0003 M DPIP with 100ml distilled water BUFFERS pH 5 buffer – 1ml solution 1 to 49ml of solution 2, mix – add 50 ml distilled water pH 7.3 buffer – 75ml solution 1 to 25ml solution 2, mix – add 100ml distilled water pH 9 buffer - 10ml solution 1 to 10ml distilled water Stopwatch Enzyme preparation: (Wright, 2005) Chicken hearts were prepared according to notes in Lab (Wright 2005). This liquid formed the enzyme. A rack containing 3 test tubes were arranged containing: tube 1 – 5.8 ml pH5 buffer 1 ml 0.1M succinate .2 ml enzyme tube 2. - 5.8 ml pH7.3 buffer 1 ml 0.1M succinate .2 ml enzyme tube 3. - 5.8 ml pH9 buffer 1 ml 0.