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Does temperature have an effect on the activity of dehydrogenase enzymes in yeast cells?

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Introduction

The Effect Of Temperature On Enzyme Activity Hypothesis: Does temperature have an effect on the activity of dehydrogenase enzymes in yeast cells? Aim: The aim of this experiment is to show the relationship between temperature and the rate of activity of dehydrogenase enzymes in two different yeast types ('Bakers' and 'Brewers'). We can then compare the results of the two different types of yeast to see which type is more affected by changes in temperature. Triphenyl tetrazolium chloride (TTC) is an artificial hydrogen acceptor, or redox indicator. When oxidised, TTC is colourless, but when it is reduced, TTC will form red, insoluble compounds called formazans. This colour change therefore shows the presence of active dehydrogenase enzymes in yeast cells. The temperature of the TTC solution and yeast suspension will affect the rate at which this colour change occurs, which in turn will show how the activity of dehydrogenase enzymes in different yeast cells changes. Background Theory: Enzymes are tertiary protein structures made up of a single polypeptide chain. The polypeptide chain is folded into a precise shape, giving enzymes their specificity. Enzymes maintain this permanent shape by a range of bonds holding them together, including disulphide bridges, ionic bonds and hydrogen bonds. Enzymes are specific to the reactions that they catalyse, so the active site on an enzyme has a particular shape into which a specific substrate will fit. ...read more.

Middle

The rate of reaction will rapidly decrease as the enzymes are given so much kinetic energy, they start to change shape so the substrates don't fit in exactly anymore. They change shape because the bonding becomes irreversibly changed so the active site is permanently damaged. The experiment will eventually reach a temperature where the enzymes will be totally denatured and will have completely changed shape, so the rate of reaction will be zero. Outline Method: This experiment is designed to show the relationship between temperature and the rate of activity of dehydrogenase enzymes in different yeast cells. Triphenyl tetrazolium chloride (TTC) is an artificial hydrogen acceptor, or redox indicator. When oxidised, TTC is colourless, but when it is reduced, TTC will form red, insoluble compounds called formazans. This colour change shows the presence of active dehydrogenase enzymes in yeast cells. The temperature of the TTC solution and yeast suspension will affect the rate at which this colour change occurs, which in turn will show how the activity of dehydrogenase enzymes in different yeast cells changes. What am I going to change? Why? INPUT VARIABLE The temperature of the TTC solution and yeast suspension. The yeast to be used ('bakers' and 'brewers') I am going to change the temperature to determine what sort of effect it has on the activity of dehydrogenase enzymes in yeast cells. By using two different types of yeast, I can see how the rate of reaction differs with varying temperature, between the two different types of yeast. ...read more.

Conclusion

At extreme pH values the enzyme will become denatured, and the shape of the protein molecules are altered as the hydrogen bonds and sulphur bridges are broken or formed. I can control this by using the same pH of enzyme and substrate from the same bottles of their solutions, and double check by using universal indicator paper. ? Volume - I must keep the volume of the yeast suspension and the TTC solution the same. If I put a large volume of TTC into a test tube and react it with the yeast at a set temperature, the rate of this reaction would be faster than if I put a small volume of TTC into a test tube and reacted it with the same yeast at the same temperature. To control this I will measure the volume (in cm3) using a measuring cylinder of each solution. Reliable results: Range of temperatures (oC): 10 oC, 20 oC, 30 oC, 40 oC and 50 oC. (Measured with thermometer) Types of yeast: 'Bakers' and 'Brewers'. Concentration of enzyme and substrate (mol):Kept the same throughout. Recorded at each set temperature. Volume of enzyme and substrate (cm3): Kept the same throughout. Recorded at each set temperature. (Measured with measuring cylinder) pH of enzyme and substrate: Kept the same throughout. Recorded at each set temperature. Number of repetitions of each yeast at the set temperature: 3 Risk Assessment and Ethical Considerations: See 'Material Data Safety Sheet' for TTC. Always wear safety goggles to prevent solutions splashing into eyes. ...read more.

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