pH - Enzymes function at different pH values. In neutral conditions the amount of oxygen gas given of in an enzyme-catalysed reaction will increase.
Concentration - In concentrated solution there are more collisions between each particle, so the reaction occurs more quickly.
Temperature - Reactions go faster as temperature rises. The rate of reaction also increases as the temperature rises, but with enzyme-catalysed reactions the reaction rate starts to decrease when the temperature is above 40 C. This is because enzymes are proteins and their structures start to damage above 40 C.
Surface Area - Reactions can react faster when solids are cut into smaller pieces. This is because there is more surface area which is exposed. The more surface area there is, the more collisions that take place between particles so the reaction rate is much quicker.
Enzymes are biological molecules that catalyze many different chemical reactions. With few exceptions, all enzymes are proteins and each enzyme is specific to a certain chemical reaction. Enzymes must maintain a specific three dimensional structure in order to function properly. If an enzyme's structure is altered (by heat or harsh chemicals) it may not function at all. This breakdown (denaturation) of an enzyme's structure may be fatal (your body cannot withstand a fever over 108 degrees for very long). The enzyme I used in this experiment is amylase, which is commonly found in saliva and germinating seeds. It catalyzes the breakdown of starch. When amylase reacts with starch, it cuts off the disaccharide maltose (two glucose molecules linked together). As the reaction progresses, less starch will be present and more sugar (maltose) will be present. In lab, the activity of amylase was observed by using iodine. Iodine reacts with starch to form a dark brown/purple color. As amylase breaks down starch, less and less starch will be present and the color of the solution (if iodine is added) will become lighter and lighter.
Hypothesis
Apparatus
- Amylase solution, 0.1 per cent
- Starch solution, 1.0 per cent
- Distilled water
- Iodine in potassium iodide solution
- White tile and glass rod
- Pipettes
- Test tube and rack
- Water bath
- Thermometer
- Stopwatch
Method
Firstly, prepare four different concentrations of enzyme solution:
Set up water bath at 35°C. Then pipette 5cm³ of undiluted enzyme solution and 5cm³ of starch solution into another test tube. Stand both tubes in the water bath and leave for several minutes to reach the temperature of the water bath. Take the tubes out and mix the two solutions together, then replace the mixture into the water bath and start the stopwatch. At intervals of one minute, remove a drop of the mixture in the water bath and test it with iodine solution on a white tile. Continue the experiment until the mixture fails to give a blue-black colour with iodine solution. Repeat this procedure with the other concentrations of amylase, using the same amount of each solution.
Results