Biology: Experiment- The Effect of Temperature on the Enzyme Rennin

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Aim: The aim of the experiment is to test the effect temperature has on the activity of the enzyme rennin.

Hypothesis: I believe the rate of reaction will speed up as the temperature increases until it reaches about 37oC, which is the body temperature, where it will begin to slow down and stop reacting. I believe this will occur because enzymes have a temperature range at which they work best in and once the temperature goes out of this range the enzyme will stop working.

Introduction:Enzymes are made up of proteins which are produced within living cells and act as catalysts which speed up chemical reactions. They are made up of long chains of amino acids containing carbon, hydrogen, oxygen and nitrogen. Enzymes are structured to be unique to a few but often only one substrate therefore being specific to one type of reaction. A substrate is the molecule that an enzyme acts upon. An enzyme has an active site which is shaped for a specific shaped substrate. The substrate and the enzyme bind together at the active site and form an enzyme-substrate complex. This then breaks down to form the products, releasing the enzyme. During the reaction the enzyme does not undergo change.

Most organisms can only survive within certain temperature ranges. For reactions to occur substances must collide with the correct orientation and necessary amount of energy, called the activation energy. The role of the enzyme is to lower the activation energy which therefore allows chemical reactions to take place inside organisms without the temperature having to be so high as well as speeding up the reaction. Every enzyme has a certain temperature range where it can work most efficiently with an optimal temperature at about 37.5 0C for most enzymes within the body. Once the temperature goes above the enzymes temperature range, the enzyme will begin to denature as intermolecular and intramolecular bonds begin to break as the kinetic energy intensifies as the temperature increases. Once the enzyme in denatured it cannot be reversed.

Rennin is a protein digesting enzyme which is produced in the stomach of mammals such as cows. In the cows fourth stomach its function is to extend the amount of time the milk remains in the stomach by thickening it. It is used in this experiment as it catalyses the conversion of the protein of milk called caseinogen to produce the compound casein. The casein will curdle the milk making it lumpy. As rennin is an enzyme it will be specific to a certain temperature therefore the rate at which the milk goes lumpy will demonstrate the effect different temperatures will have on enzymes.

Materials:-6 Test tubes-Full cream milk-Stop watch-Junket powder-Saucepan-Water-Thermometer-100ml Measuring cup-2 x 10ml Measuring cups-Tea spoon-Ice cubesMethod:1.Set up apparatus. Pour water into a saucepan and place on stove top.

2.Pour 5 ml of milk into six test tubes and keep in fridge.

3.Make enzyme mixture by measuring 25ml of water with the 100ml measuring cup and mixing in 1 level teaspoon of junket powder and set aside.

4.Heat water in saucepan to 30oC using a thermometer. Once the water in saucepan has reached the desired temperature turn off the stove.

5. Get two test tubes with the milk and place in sauce pan making sure they sit so no water can enter the test tubes. Wait for the milk to reach 30 oC, using the thermometer.

6.Stir then pour 2.5ml of the enzyme mixture using the 10ml measuring cup into one of the test tubes still not allowing any water from the saucepan into the test tubes. The test tube without the enzyme mixture is the control.

7.Start the stopwatch and time how long it takes to clot*. Constantly check temperature, and turn up the heat if the temperature starts to drop.

8.Record time in table.

9.Repeat steps 4 7 two times changing the temperature to 40oC and 50oC.

10.Using the same saucepan, fill with water and ice cubes until it has reached 10oC, using a thermometer....
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