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# Determine the effect of temperature upon respiration of Yeast.

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Introduction

Group number: 2 Yeast Investigation PLAN Aim: To determine the effect of temperature upon respiration of Yeast. Prediction: I predict that the respiratory rate of the yeast will increase in speed as the temperature of the water increases. However, it may reach a peak, and slowly decline as the temperature increases further. My reason for the above prediction is that, anyone who has cooked, knows that yeast is supposed to respond in warm water, so I believe that the warmer the water, the more bubbles of CO� produced. Also, the oxygen produced in the initial stages of the experiment will allow the speed of reaction, of converting glucose to energy, to increase additionally. It will decrease once all the material has reacted, and/or because the temperature is too high for the yeast to respire as the heat has denatured the yeast's enzymes and they can no longer fit their substrate, and therefore decreasing their capability to work. Method: The yeast is put into a glucose solution, this is because the glucose provides the energy for the yeast to respire. We will take 7 readings of heated water (starting with 10�c), each with a 10�c interval, and observe how many bubbles of CO� each temperature allows the yeast, placed in the beaker of water, to produce. ...read more.

Middle

If we had continued with the experiment using higher temperatures, we wouldn't have had any CO� bubbles being produced. Between the temperatures of 10�C and 40�C, the graph shows that the yeast respires rapidly , producing more CO� than between the temperatures of 40�C and 70�C, where the level of CO� produced decreases.� Therefore, the yeast respires at its best, proved by our results, when the solution of yeast and glucose is at 40�C. There is a big difference between the amount of CO� produced between 10�C-20�C and 20�C-30�C. There is a lower rate of reaction for the first process of the experiment, this could be because there is not enough energy given for the enzymes to work as the temperature is too low. The change in the second process of the experiment is caused by the oxygen produced in the initial (first process) stages of the experiment. It allowed the speed of reaction, of converting glucose to energy, to increase as the glucose molecules became more plentiful as the concentration increased, so the probability that the yeast enzymes will come into contact and react with the molecules is higher. Before 40�C the rate of reaction increases gradually :- all the enzymes are protein chains of amino acids, along the chains, there are active sites where contact between the enzyme and its substrate take place. ...read more.

Conclusion

We handled the experiment carefully and with detail so that we could be satisfied with what results we would obtain. Factors that had an affect on the experiment were: doing the whole experiment in several days, the room temperature or apparatus used could have been different and so, not making it a fair test. Also, the percentage of glucose in the yeast affected the experiment because, on different days, there might have been more/less glucose than in the former experiment, which had been performed on a different day. The depth of the test tube in the beaker affected how many bubbles could be released. To improve this and thus, our results, we should have done the experiment in one day, using the same apparatus throughout. We could have made sure that the test tube was at the same, certain depth in the beaker of water for each experiment and made sure that the solution of yeast and glucose had been properly mixed. Also to check all results, performing the experiment even more times and in better circumstances away from being disturbed would increase the certainty of the results produced. I think that further research on Yeast and how the experiment should have been performed and carried through in class would have helped me to understand exactly how the experiment worked and what could be obtained from it, hence, making me more confident concerning my attitude towards the experiment and understanding exactly what to do. ...read more.

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