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5. Enzymes
A section of Biology, 0610
Listing 10 of 248 questions
A student investigated the effect of lactase on three different liquids: • milk • lactose‑free milk • sucrose solution. The student used an indicator to test for the presence of glucose. A sample of each liquid was tested before and after treatment with lactase. The indicator turned brown in the presence of glucose. The indicator remained blue in the absence of glucose. Table 4.1 shows the results of the tests. Table 4.1 liquid colour before treatment with lactase colour after treatment with lactase milk blue brown lactose‑free milk brown brown sucrose solution blue blue Explain the results for the three liquids shown in Table 4.1. The student kept the solutions at a temperature that was close to the optimum during the investigation. Using your knowledge of the effect of temperature on enzyme activity, explain why this was important. As part of a balanced diet, some governments recommend that children drink milk that has vitamin D added to it. Suggest the dietary reasons for this advice. Describe what is meant by a balanced diet.
0610_s24_qp_41
THEORY
2024
Paper 4, Variant 1
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Microorganisms in the soil release enzymes to digest dead leaves. Explain how enzymes catalyse chemical reactions. Protease and cellulase are two enzymes secreted by soil microorganisms. Protease digests protein. Suggest what part of the dead leaf cells are digested by the enzyme cellulase. Table 6.1 shows the results of a study comparing the decomposition of dead leaves at two locations A and B. Table 6.1 location A location B protease activity / µmol min–1 cellulase activity / µmol min–1 soil pH 6.0 3.5 soil water content / % Compare the enzyme activity at location A with the enzyme activity at location B. You will gain credit for using the data from Table 6.1 to support your answer. Suggest possible reasons for any differences in the enzyme activity at location A and location B. Describe how nitrogen in proteins in dead leaves is recycled to be absorbed by plants. Microorganisms also process and convert atmospheric nitrogen to form a nitrogen compound that can be absorbed by plants. Name this process of converting atmospheric nitrogen. Explain how this process happens.
0610_w14_qp_31
THEORY
2014
Paper 3, Variant 1
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Pepsin is a protease enzyme found in the alimentary canal. Name the product formed from the digestion of proteins by protease enzymes. State the organ in the alimentary canal where pepsin is secreted. A biologist performed an experiment to find the optimum pH for the activity of pepsin. The enzyme activity was measured in four test-tubes. Each test-tube contained a 1 cm3 cube of cooked egg white which contains protein. shows the four test-tubes. The biologist measured the time taken for the complete digestion of the cubes of cooked egg white. pH 1 pH 3 pH 5 pH 7 solution of enzyme at a given pH cube of cooked egg white The biologist ensured all the cubes of cooked egg white were exactly the same size. Suggest why. Temperature must be controlled in this experiment. Describe how temperature could be controlled. The same experiment was performed with trypsin, another protease enzyme. Predict the optimum pH for trypsin. Enzymes, such as proteases, are important in digestion. Describe in detail how enzymes function, using other digestive enzymes as examples.
0610_w16_qp_41
THEORY
2016
Paper 4, Variant 1
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Questions Discovered
248