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How does temperature effect the rate of enzymes?

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Sana Javed T11EP Biology Coursework How does temperature effect the rate of enzymes? Aim I am going to investigate the effect of temperature on enzymes, using a potato as a catalyst. The potato contains the catalyst CATALASE. An enzyme is a protein molecule that speeds up chemical reactions in all living things. Without enzymes, these reactions would occur too slowly or not at all, and no life would be possible. They are reusable. Basically they are like biological catalysts. Enzymes are classified into several categories, such as hydrolytic, oxidising, and reducing, depending on the type of reaction they control. Hydrolytic enzymes speed up reactions in which a substance is broken down into simpler compounds through reaction with water molecules. Oxidising enzymes, known as oxidises, speed up oxidation reactions; reducing enzymes speed up reduction reactions, in which oxygen is removed. Catalase is present in the peroxisomes of nearly all-aerobic cells. Peroxisomes break down fatty acids and amino acids. These reactions produce hydrogen peroxide that could harm cells if it were allowed to persist. The enzyme (catalase) breaks down the hydrogen peroxide to water and oxygen, both of which can be used by the cell. It serves to protect the cell from the toxic effects of hydrogen peroxide by catalysing it into oxygen and water. The reaction we will be doing is: Catalase Hydrogen Peroxide ---> Water & oxygen Enzymes work by joining the substances together to make the reaction work faster. ...read more.


For a mammal this is around 35-37 c. as the temperature gets higher the rate of reaction will start to decrease because the enzyme is becoming denatured. The structure of the enzyme is changing and the active site will become destroyed as the temperature increases, then the substrate (hydrogen peroxide) will no longer be able to fit into the active site and the reaction will then stop (lock & key mechanism). This is shown in the graph below. The rate initially goes up as the temperature increases this is because the temperature changes the rate, as the temperature rises, the movement of enzyme molecules and substrate molecules increases. This causes more collisions between enzyme and substrate, and the result is the formation of more product, as the rate of reaction increases. Then the temperature rises beyond a certain point and the enzyme activity declines gradually because the heat, which destroys the active site so the lock and key mechanism cannot take place, as it denatures the enzyme. Also, if I apply twice as much heat there will be twice as much particle vibration therefore the reaction will happen twice as quickly. This is the kinetic theory. In the graph above we can see that the enzyme activity has increased quite quickly and as It reaches the optimum temperature which is 37 around this temperature the activity starts to fall as the enzyme has reached the temperature where it works best and now it is starting to become denatured as the temperature starts to cook the active site which is ...read more.


The anomalous results which I found could have been caused by many things such as the losing of gas during the experiment e.g. the bung might not have been tight enough which could of let some of the gas given off into the temperature rather than into the burette. Also as I said before the temperature wasn't as accurate as I could have been this could have caused there to be anomalous results. If I look at my graph I can see two main anomalous results, which are at 50 and 60, they were firstly too close together showing that the gas given off was mostly the same amount, this may be due to that temperature was not correct or gas was given off into the atmosphere. Though my results are in line with those that I predicted. The graph indicates the rise in temperature up to a point leads to an increase in oxygen production. This is in lint with the kinetic theory. However it is very clear that after a certain temperature is reached the enzyme actually stops and starts to decrease this supports my theory of lock & key fit. Overall, due to reliable repeats and in general predictions being confirmed I feel my results are reliable. Further experiments that I could do, would be to change the catalase used. Also, I would have done the experiment with a piece of liver too, just to make sure that the catalyse activity is the same in the liver as the potato. Although, I already know from what I have been taught, that the liver would give similar results to the potato. Sana Javed T11EP 02/05/2007 ...read more.

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