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An investigation into how enzyme concentration (catalyse in a potato) affects the rate of reaction an enzyme catalysed reaction.

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AS BIOLOGY COURSEWORK Investigation into how enzymes concentration affects the rate of reaction Aim: An investigation into how enzyme concentration (catalyse in a potato) affects the rate of reaction an enzyme catalysed reaction. Theory Enzymes are biological catalysts that are composed of globular protein molecules. 'A catalyst is a molecule which speeds up a chemical reaction, but remains unchanged at the end of the reaction.' (Cambridge Biology 1 by Mary Jones.) As an enzyme is a globular protein the molecule is curled up so the non-polar R groups point away from surrounding water into the centre of the molecule. Catalase is an enzyme made up of protein molecules. A catalase speeds up a reaction from the substrate. Catalase is present in the majority of living things including carrot, liver and potato. Hydrogen has the chemical formula of H2O2. It is a colourless liquid used in rocket propellant, bleaching textiles and in the manufacture of other chemicals. Hydrogen peroxide is a toxic and the catalase decomposes it down into the non-toxic water and oxygen. This reaction is important to the cell where it occurs because hydrogen peroxide would poison and kill the cells. The potato enzyme will force the hydrogen peroxide to decompose into water and oxygen. This is a natural process that occurs and will carry on reacting until the substrate runs out. The enzyme does not run out and the surface area of the potato is directly proportional to the amount of enzyme as enzyme is present in every cell of potato. If a substrate finds an enzyme it will try to fix into it's active site, this is called 'complex'. If the enzyme does not fit, it cannot be broken down. When the enzyme fits into the substrate, a reaction will occur .The enzyme chemically rearranges the molecules, and breaks the substrate into small soluble products. If the experiment contains too much acid the Ph level will drop. ...read more.


8ml of hydrogen peroxide and 12ml of water (1.2%) 4ml of hydrogen peroxide and 16ml of water (0.6%) I will measure the rate of the reaction by measuring the amount of bubbles that occur in a tube every 30 seconds for 5 minutes. 2H2O2 catalyse 2H2O + O2 Diagram Method 1. I will find all the equipment shown on page two and put it together, as shown in the diagram above. 2. I will then fill up the bowl approximately half full with water from a tap. 3. I will then clamp the conical flask next to the bowl. 4. I will take the conical flask's tube and place it in the bowl. 5. Next I will fill up the measuring cylinder with water from the bowl. 6. I will place the measuring cylinder over the tube and hold it in place for the rest of the experiment. 7. Then I will use the cork borer to cut the potato, I will do this on the tile. 8. The potato will be cut from size 2 borer. 9. Then using a ruler I will cut the edges of the potato so it is 5 cm long. It is important that each piece of potato has the same surface area exposed, so each test will have the same enzyme present. 10. I will put the potato in the conical flask. 11. Then I will add the weakest dilution first. 12. I will put the cork with the tube on the conical flask. 13. Then I will start the stopwatch. 14. I will record the amount of bubbles that are present in the measuring cylinder every 30 seconds. 15. I will do this for 5 minutes. 16. I will repeat this 3 times, each time, I will use a stronger dilution. The reaction will occur in the conical flask, as the enzyme from the potato will react with the hydrogen peroxide. ...read more.


* Stopwatch - to be able to accurately record the amount of oxygen released every 30 seconds. * Safety goggles - to avoid hydrogen peroxide coming in contact with eyes. * Potato - contains the catalase that show how substrate concentration affects the rate of reaction. * Scalpel - to cut the potato cylinders into exact weight. * Glass rod - to remove from cork borer. * Cork - to prevent oxygen escaping. * Delivery tube - to direct oxygen released. * Clamp and stands - to hold the measuring cylinder used to collect oxygen. * Water - to show how much oxygen has been produced. * Bowl - to hold the water so oxygen can be collected in the measuring cylinder. * Cork borer (size 2/6mm) - to obtain accurate potato cylinders. * Electrical balance - to weigh potato pieces for exact weight. * Thermometer - to make sure the temperature is always 25o C when carrying out the experiment. Diagram Method 1) Set up the experiment as shown in the diagram. Only start the experiment when the temperature is 25oC. Use the 6mm radius potato borer and cut potato cylinders, then use the scalpel, electric balance and the tile, cut the potato cylinder into 3cm in length and weigh so they all weigh the same, place in the test tube making sure there is no skin on the potato. Fill the syringe with the amount of hydrogen peroxide required for the substrate concentration and make sure there is no air in the gas syringe. 2) Inject the hydrogen peroxide into the test tube and start the stopwatch. Record the volume of oxygen collected from the gas syringe every 30seconds for 10 minutes onto an appropriate table. 3) Clean the conical flask. Once dry, repeat the experiment twice more making sure it is done at 25oC with no skin on the potato and with the same age hydrogen peroxide, temperature and surface are of potato. 4) Do the same with the other concentrations of substrate and record the results at the same intervals. ...read more.

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