Iii what conclusions can be drawn from the graph

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Chapter 18 / Exercise 3
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(iii) What conclusions can be drawn from the graph about the effect of temperature on amylase activity? (3 marks) (iv) If you want to store the mixture of crushed grains and water with minimal reaction so that it can be used several days later, what temperature would you choose? Why? (3 marks) (v) Suggest another method to estimate the amylase activity for this investigation. (2 marks) (HKCEE 2000) 5. A kind of Chinese dessert is made by mixing milk with ginger juice so that the milk becomes coagulated. The coagulation of milk is due to the conversion of a soluble milk protein into an insoluble form. To find out the conditions for milk coagulation, a person mixed milk at different temperatures with some fresh ginger juice. The mixtures were observed for 15 minutes to see if coagulation would occur. The results are shown in the table below: The results of the experiment are shown below: (i) Explain why the paper discs rose to the surface of the solution in some of the tubes. (2 marks) (ii) (1) Work out the rate of reaction from the value of T for each tube. Tabulate your answer. (2 marks) (i) Referring to the above results, describe the effect of milk temperature on the rate of milk coagulation by ginger juice. (3 marks) (2) Using the data obtained in (1), plot a graph on graph paper to show the effect of pH on catalase activity. (3 marks) (ii) How would you explain the action of fresh ginger juice in bringing about the coagulation of milk? Give evidence to support your answer. (2 marks) (iii) (1) Based on your graph, estimate the optimum pH of catalase. (1 mark) (iii) Milk protein also coagulates at low pH. In which part of the alimentary canal does this coagulation occur? Based on your biological knowledge, suggest why the coagulation of milk protein can facilitate its digestion in that part of the alimentary canal. (3 marks) (2)In order to get a more accurate estimate of the optimum pH, what further work would you carry out in this experiment? (1mark) (HKCEE 2002) (iv)A sample of bean extract was refrigerated at 4 ° C and then allowed to warm to room temperature. If the experiment was repeated using this sample, would the catalase activity be different from that of the previous experiment? Explain your answer. 6. The following shows the procedure of an experiment to study the effect of pH on the activity of catalase extracted from bean seedlings: (2 marks) (HKCEE 2003) 7. One day, when Keith and Jane walked past a fresh fruit juice shop, Keith noticed that some pears were cut into pieces and stored in a tank of water before use. (a) Keith thought that the shopkeeper stored the cut pears in water in order to extract more juice. Explain the Past HKCEE Questions Cell Activities P. 2 / 8
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Chapter 18 / Exercise 3
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Past HKCEE Questions Cell Activities P. 3 / 8

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