There will be an optimal point when all the active sites are filled, at this point the reaction will stop, as all the hydrogen peroxide will have been broken down leaving only Catalase, water and oxygen. I predict the more you increase the surface area of Catalase, the more oxygen produced, because the hydrogen peroxide has more surface area to collide with, causing a faster rate of reaction. Apparatus/equipment needed Size 6 hole borer A tile 2 x measuring cylinders Conical flask Bung + delivery tube Knife Potatoes Stop watch Hydrogen peroxide Boss + clamp + stand Water Plastic container
Method 1. Put on safety glasses 2. Set up equipment as shown above 3. Use the hole borer and bore out pieces of potato then cut into 2cm lengths. 4. Put 1x2cm piece of potato in the conical flask with 50ml of hydrogen peroxide. Replace bung immediately and start stopwatch for 5 minutes. 5. After 5 minutes pull out bung, read the measurement on the upside down measuring cylinder. Record your results 6. Empty and rinse conical flask. 7. Refill upside down measuring cylinder with water 8. Repeat steps 3-7 another 4 times but in step 4 add another 2cm piece of potato each time.
Perform the experiment three times 10. Take the room temperature at the start middle and end of the experiment 11. Repeat the steps 3-7 this time omit the potato, this gives the control result. You only need do this once. RESULTS Oxygen levels SURFACE AREA OF POTATOE Control 0 1X2CM 7. 39cm? 2X2CM 14. 78cm? 3X2CM 22. 17cm? 4X2CM 29. 56cm? 5X2CM 36. 95cm? 1ST results 4ml 4ml 9ml 10ml 13ml 2ND results 4ml 6ml 8ml 10ml 12ml 3RD results 3ml 5ml 9ml 12ml 14ml I collected extra results from 2 class members.
They do this by reducing the amount of activation energy that’s needed, making reactions happen at a lower temperature. Enzymes are effective in the body, because they lower the amount of energy required for a reaction to happen All enzymes have an active site. (Johnson 2013) This is where another molecule can bind with the enzyme. This molecule is known as the substrate. When the substrate binds with the enzyme, it converts the substrate into one or more products. Enzymes are specific to their substrate, because the shape of their active site will only fit the shape of their substrate.
It is said that the enzymes active site is complimentary to their substrate. This is known as the lock and key theory. If the substrate’s shape doesn’t match the active site shape, then reaction won’t be catalysed. Another theory is the Induced fit theory it is when the substrate and enzyme fit together but the enzyme-substrate complex changes shape a little to complete the fit. This locks the substrate even more tightly to the enzyme. They are 2 types of inhibitors that can affect the rate of enzyme action. Competitive inhibitors which have a similar shape to the normal substrate.
The competitive inhibitor can form a complex with the enzymes active site preventing the normal substrate binding, so normal reaction cant take place. The second is the non competitive inhibitor which distorts the shape of the active site. The inhibitor molecule binds to the enzyme, changing its shape and the shape of the active site, meaning the normal substrate can’t bind. Enzymes have an optimum temperature and ph level at which they work best. If the temperature is too high or the ph level is too high or too low, the enzyme becomes denatured.
Enzymes are globular proteins, with a complex tertiary structure, in which polypeptides are curled up into a ball shape; they are compact and soluble so they are easily transported around the blood. The 3d shape of the enzyme molecule is important, as if the shape is changed, the enzyme cannot bond with the substrate. The enzyme shape is maintained by hydrogen bonds and ionic forces. Catalase is a globular protein molecule that is found in all living cells. (Bowness 2009) Catalase breaks down hydrogen peroxide into harmless water and oxygen gas.
Hydrogen peroxide is a highly reactive chemical often used for bleaching and cleaning minor wounds. Hydrogen peroxide is continually formed as a by product of a chemical reaction in living cells, however is highly poisonous and must be removed or broken down immediately by the cells. Hydrogen peroxide is converted into two harmless substances, oxygen and water with the help of the enzyme catalase, which speeds up the reaction. The more substrate molecules present, the more collisions happen, and more enzyme activity until all the active sites are full causing the reaction to slow down.
The more enzymes present the reaction speeds up The more active sites available for more collisions Random movement of the substrate speeding up the reaction until only the enzyme and by products left. From my table of results and graphs I can clearly see that the more surface area of catalase the more oxygen created in the 5 minute periods. This is because the more surface area of catalase the more active sites available to bind with the substrate Hydrogen peroxide, meaning more collisions breaking down the substrate faster.
I could only half prove my theory because I stopped adding enzyme at a surface area of 36. 95cm? so there was still an adequate amount of substrate to enzyme to fill active sites If I was to repeat the experiment. I would use a different method of using the enzyme. I would extract the enzyme from the potato using a centrifuge, because even though the potato pieces were all cut using a borer and were all measured to exactly 2cm in length, you can’t be sure the amount of catalayse in each piece was exactly the same.
One piece could have had twice as much as another piece. Using a centrifuge would mean you could use the exact amount of catalase each time. I wouldn’t change any think else because I feel I obtained true and accurate results proving my theory right. References: Johnson. M. D(2013)Human biololgy:concepts and current issues 7th edition, Benjamin cummings publishing Bowness. E. (2009)A2-LEVELBiology:coordination group publications LTD