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Investigate the effect of temperature on dehydrogenase activity in yeast. At which temperature is tetrazolium chloride (TTC) discoloured most rapidly?

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Introduction

Investigate the effect of temperature on dehydrogenase activity in yeast. At which temperature is tetrazolium chloride (TTC) discoloured most rapidly? Introduction Enzymes are composed of many specialised organic substances, such as polymers of amino acids, which act as catalysts to regulate the speed of the many chemical reactions involved in the metabolism of living organisms. Individual enzymes are naming by adding -ase to the name of the substrate with which they react. There are many types of enzymes such as... hydrolytic, oxidising, and reducing. * Hydrolytic... speed up reactions in which a substance is broken into simpler compounds through reaction with water molecules. * Oxidases... these are oxidising enzymes that speed oxidation reactions. * Reductases... reducing enzymes that accelerate reduction reactions. "Enzymes are highly specific in their actions. Each enzyme catalyses either a single chemical reaction or a group of closely related reactions" Enzymes operate by attaching themselves to their substrate molecule at the active site. The theory that enzymes and substrates bind is called the 'lock and key' hypothesis. As the enzyme (A) and the substrate (B) form a complex (AB), the substrate is raised in energy to a transition state, and then breaks down to products (C) plus an unchanged enzyme (E)... A + B --> AB --> C + E In this experiment the only variable which can be changed is the temperature, to show that it is the only influence on the dehydrogenase activity. ...read more.

Middle

9. I will clean the current apparatus up and repeat the temperature again. 10. I will proceed with the remaining temperatures with their repeats. 11. After all the experiments have been finished with, the apparatus will be put away in its relevant container for cleaning. Fair test I will be ensuring that my experiment is as fair as possible by limiting the variables to just one, temperature. The volume of TTC and respiring yeast solution will be a constant. I will be repeating each temperature to ensure that the original was a valid result, and subsequently I shall be making an average of the result. This will narrow down the margin of error and increase the efficiency of my results. To make sure that I time up to the same colour change in each test I will make up on control test tube and keep it by me throughout the experiment as a point of reference. I will compare the control test tube's colouration with the current test tube to make sure that my timing is accurate and I am timing the same colour change for each temperature. To stop any more discolouration of the control, I will put it in a beaker of ice. This will end any reactions taking place in the test tube and will keep the colour of the solution as a record. ...read more.

Conclusion

There were a few minor details that I feel could have been rectified if possible, but they would not make a big impact on the eventual results. This was the transferring of the TTC solution to the test suspension. I felt that sometimes not the full 1 cm3 was going into the solution of yeast. This could change the time. Maybe for future experiments, the bottle or container of TTC could be put into the water bath/beaker of water to reach its temperature with the test tube of yeast. Then the measurement of 1 cm3 could be taken from the bottle or container directly. This would ensure that the full 1 cm3 went into the mixture. A wider range of data points would increase the accuracy of the results and lead to a much firmer conclusion. Also, if there could be water baths at all the required temperatures hen it would be much fairer. Maybe for a experiment, tests could be done on various types of yeast and what their optimum temperature for discolouration of TTC solution, and how the enzyme activity compares to that of other types of yeast with altering temperature. You could then compare all the data together to come to another conclusion about dehydrogenase activity. I am sure that there will be some differences in time between the different types of yeast. This could definitely be explored further with other yeast; for example, you could to it with brewer's yeast. ...read more.

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A clearly written account of the investigation. The author has a good knowledge and understanding of the background theory. The discussion of trends and results could have been more thorough, however.

Marked by teacher Adam Roberts 05/09/2013

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