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Use of a Redox Indicator to show Dehydrogenase Activity

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Introduction

Use of a Redox Indicator to show Dehydrogenase Activity Hypothesis: As the temperature increases, the time taken for the colour change to occur will decrease. Introduction: Triphenyl tetrazolium chloride (also known as T.T.C) is an example of an artificial hydrogen acceptor. It is a redox indicator which is colourless when oxidised, however when reduced, it produces a red, insoluble precipitate called 'formazans'. T.T.C can therefore be used to investigate the enzyme activity of dehyrogenase enzymes by showing a colour change when they are present. The purpose of this experiment is to see what effect temperature has on the activity of dehydrogenase enzymes within yeast cells. Materials/Apparatus: * Actively respiring yeast suspension. This is prepared by adding 10g of dried yeast to 1dm3 of distilled water, followed by mixing in 50g of glucose. This mixture should be allowed to stand for 24 hours before the experiment takes place. ...read more.

Middle

Allow all solutions to reach the same colour before removing them from the water baths. Method: Prepare a solution of yeast cells by adding 10g of dried yeast to 1dm3 of distilled water, followed by mixing in 50g of glucose. This mixture should be allowed to stand for 24 hours before the experiment takes place. Once the yeast suspension has been allowed to stand for 24 hours, the froth should be removed and discarded. Set up a water bath by adding ice cubes to cold water, until the water has reached 10degrees. Continue to measure the temperature with a thermometer ensuring that the temperature is maintained. Set up separate incubators at 30, 40, 50 and 60 degrees. Using a syringe, place 5cm of yeast suspension into three separate test tubes and place in the incubator. Leave for several minutes and then add 0.5cm of T.T.C into each solution and place them back into the incubator set at 30degrees. ...read more.

Conclusion

The temperature at which the dehydrogenase enzymes worked at their quickest was 50 degrees. This indicates that 50 degrees is the optimum temperature for the enzyme activity to take place as the colour change took slightly longer when placed in a water bath set at 60 degrees. This may be due to the fact that some of the dehydrogenase enzymes could have been denatured due to the high temperature. However, it is not quite clear whether 50 degrees is the optimum temperature for the enzyme activity to take place because this experiment took place using a limited amount of temperature ranges. If this investigation was to be repeated, a wider range of temperatures could be used so that an optimum temperature could be established. Overall, the results from this experiment support the hypothesis and therefore have provided successful and sufficient data which have confirmed the predictions that were made prior to the investigation taking place. ?? ?? ?? ?? ...read more.

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Response to the question

The candidate answers the question well. They could have increased the scientific depth of knowledge used to explain their hypothesis by for example including facts about collision theory and temperature. Their assessments and layout of the experiment are done ...

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Response to the question

The candidate answers the question well. They could have increased the scientific depth of knowledge used to explain their hypothesis by for example including facts about collision theory and temperature. Their assessments and layout of the experiment are done very well.

Level of analysis

The candidate makes a good hypothesis and explanation in their introduction, but they do not account for when the temperature becomes too high that the enzyme denatures, so the reaction will not proceed at the fast speed they anticipate. The apparatus needed is explained well although the colour change expected should be better explained as this is open to interpretation which may be wrong. The method is explained well, but would be clearer and easier to follow in given steps/bullet points. Their conclusion is adequate because it describes their results well using scientific knowledge. Their evaluation is too brief, and should be stand alone, not within the conclusion for the candidate to show true assessment of how the experiment went.

Quality of writing

Punctuation, grammar and spelling all to a good level. Tone and layout overall to a high clear to read standard.


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Reviewed by skatealexia 16/09/2012

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