5. Enzymes
A section of Biology, 0610
Listing 10 of 248 questions
For Examiner's Use A student investigated the effect of changing pH on the rate of reaction of a digestive enzyme. Define the term enzyme. Table 7.1 shows the results of this investigation. Table 7.1 pH rate of reaction / arbitrary units Plot the results as a line graph on . rate of reaction / arbitrary units pH For Examiner's Use Suggest where in the human digestive system this enzyme would have been most active. The investigation at pH 3 was repeated but the enzyme was boiled before its use. Suggest how and why the results would have been different.
0610_s07_qp_2
THEORY
2007
Paper 2, Variant 0
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For Examiner's Use In Sichuan, in China, a sauce is made from broad bean seeds that have germinated and then have been left to ferment. shows a germinating broad bean seed. K L M N Name K to N. K L M N Broad beans contain starch. The germinating beans are colonised by yeasts and other fungi, such as Aspergillus. Aspergillus grows over the surface of beans and digests starch. It has a body made of thin threads that secrete enzymes, such as amylase. Name the thin threads that make up the body of a fungus, such as Aspergillus. For Examiner's Use The action of enzymes is often explained in terms of the ‘lock and key’ model as shown in . substrate enzyme Use the information in to explain how enzymes work to break down nutrient materials, such as starch. For Examiner's Use Enzymes in bean seeds are activated during germination. Some of these enzymes break down protein stored in the seeds. A large number of bean seeds were soaked and germinated. Researchers took samples of germinating seeds over a period of 15 days. The seeds were chopped into small pieces and crushed with water to make an extract. Equal quantities of the extracts were placed into protein solutions at pH 5 and at pH 8. The activity of the enzymes in each extract was determined by recording how quickly the protein was broken down. The results are shown in . time / days enzyme activity / arbitrary units pH 8 pH 5 Describe the activity of the enzymes in the extracts at pH 5 over 15 days. For Examiner's Use The researchers concluded that the beans contained two different enzymes that break down protein. State the evidence from for this conclusion.
0610_s12_qp_31
THEORY
2012
Paper 3, Variant 1
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The digestive system produces enzymes. Define the term enzyme. shows how the reaction rates of two different enzymes, L and M, vary when the pH changes. rate of reaction pH acidic alkaline neutral enzyme L enzyme M Use to state the pH at which each of these enzymes work the fastest. pH for enzyme L: pH for enzyme M: Table 8.1 lists the names of three enzymes found in the alimentary canal. Complete Table 8.1 by writing in the names of the substrate and one end-product for each enzyme. Choose your answers from the list. amino acids cellulose fat fatty acids glucose glycerol maltose protein starch vitamins Table 8.1 name of enzyme substrate one end-product amylase lipase protease
0610_s15_qp_21
THEORY
2015
Paper 2, Variant 1
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Complete the following paragraph about enzymes. Choose words from this list. Use each word only once or not at all. activators catalysts enzymes protein reactions unusual All enzymes are made of molecules. They control the metabolic in living organisms. The enzymes act as as they speed up processes but are not permanently changed. Enzymes are important in chemical digestion. Define the term digestion. In an investigation to measure the effect of pH on enzyme activity, a protease enzyme was mixed with solutions of different pH values. The mixtures were placed in holes cut in the centre of dishes of gelatin. Gelatin is a protein which can be stained with a coloured dye. When the protease digests the gelatin a colourless zone forms. shows a dish at the start of the experiment. shows the dishes after a period of 24 hours. stained gelatin (a protein) hole containing mixture of solution and protease dish at the start pH 2 pH 4 pH 6 pH 8 pH 10 gelatin colourless zone after 24 hours Using , state the optimum pH for the activity of this protease. Suggest the region of the alimentary canal in which this protease carries out its function. Complete the equation to explain how the protease caused the colourless zones to appear. protease The experiment was carried out at 20° C. Suggest what would happen if the experiment was carried out at 30° C.
0610_s15_qp_22
THEORY
2015
Paper 2, Variant 2
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Complete the sentences about enzymes by filling in the gaps. Use words or phrases from the list. catalysts hormones not changed prevent protein slow down speed up used up Enzymes are made of molecules. They function as which means that they chemical reactions. Saliva contains an enzyme that digests starch. A group of students used saliva to investigate the digestion of starch at different pH values. Their results are shown in . time taken for the digestion of starch / min pH At which pH does the enzyme in saliva work the fastest? How long does it take for the starch to be digested at pH 6? min The stomach produces hydrochloric acid. Use the graph to suggest why the enzyme found in saliva does not work inside the stomach. Name the enzyme that digests starch and state where this enzyme is produced. name of enzyme where produced Name one factor, other than pH, which can change the rate of enzyme activity.
0610_s15_qp_23
THEORY
2015
Paper 2, Variant 3
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Questions Discovered
248