Q1.Catalase is an enzyme found in many different tissues in plants and animals.it speeds up the rate of the following reaction.

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1 ENZYMES. DIGESTIVE SYSTEM. Thnton College NAME.. Q.Catalase is an enzyme found in many different tissues in plants and animals.it speeds up the rate of the following reaction. hydrogen peroxide water + oxygen Figure shows a 25-day-old broad bean seedling. Some students investigated whether different parts of bean seedlings contained different amounts of catalase. The students: put hydrogen peroxide into five test tubes added a different part of a bean seedling to each tube recded the results after half a minute. If there was catalase in part of the seedling, oxygen gas was given off. When oxygen gas is given off, foam is produced in the tubes. Figure 2 shows the results. Page

2 Thnton College The students made the following conclusions: most parts of a bean seedling contain catalase the seed contains a lot of catalase stems and roots have quite a lot of catalase the leaves have a little bit of catalase the seed coat has hardly any catalase. The students teacher said that the students needed to improve their investigation in der to make valid conclusions. (a) In this question you will be assessed on using good English, ganising infmation clearly and using specialist terms where appropriate. Describe how you would carry out an investigation to compare the amounts of catalase in different parts of bean seedlings. You should include details of how you would make sure your results give a valid comparison of the amounts of catalase. Page 2

3 Thnton College (6) (b) Scientists investigated the effect of ph on the activity of the enzyme catalase in a fungus. The table below shows the scientists results. ph Enzyme activity in arbitrary units Test Test 2 Test 3 Test 4 Test 5 Mean (i) Calculate the mean enzyme activity at ph 5.0. Mean =... arbitrary units (2) (ii) On the graph paper in Figure 3, draw a graph to show the scientists results. Remember to: add a label to the vertical axis plot the mean values of enzyme activity draw a line of best fit. Figure 3 Page 3

4 Thnton College (4) (iii) At what ph does the enzyme wk best?... () (iv) Predict the activity of the enzyme at ph arbitrary units () (v) Suggest why the enzyme s activity at ph 3.0 is zero. () (Total 5 marks) Q2.Lipase is an enzyme that digests fat. Page 4

5 (a) (i) Complete the equation to show the digestion of fat. Thnton College Use the crect answer from the box. glucose glycerol glycogen fat fatty acids +... () (ii) Name one gan that makes lipase. () (b) Some students investigated the effect of bile on the digestion of fat by lipase. The students: mixed milk and bile in a beaker 2 put the ph sens of a ph meter into the beaker 3 added lipase solution 4 recded the ph at 2-minute intervals 5 repeated steps to 4, but used water instead of bile. Suggest two variables that the students should have controlled in this investigation (2) (c) The graph shows the students results. Page 5

6 Thnton College (i) Why did the ph decrease in both investigations? () (ii) Bile helps lipase to digest fat. What evidence is there in the graph to suppt this conclusion? () (iii) Suggest one reason why the contents of both beakers had the same ph at the end of the investigations. () (Total 7 marks) Page 6

7 Q3.Fresh milk is a mixture of compounds including lipid, protein and about 5% lactose sugar. Lactose must be digested by the enzyme lactase, befe the products can be absbed. Lactase can be added to fresh milk to pre-digest the lactose. This makes lactose-free milk, which is suitable f people who do not produce enough lactase of their own. A student investigated the effect of changing ph and temperature on the digestion of lactose in milk. The results are shown in Tables and 2. Thnton College Table Effect of ph Table 2 Effect of temperature ph Time taken to digest lactose in minutes Temperature in C Time taken to digest lactose in minutes No digestion (a) The label on a carton of lactose-free milk states: Lactase is nmally produced in the stomach of mammals. The results in Table suggest that this statement is not true. Explain how. (2) (b) Explain, as fully as you can, the results shown in Table 2. Page 7

8 Thnton College (3) (c) Bile is produced in the liver and is released into the small intestine. Bile helps the digestion of lipid in the milk. Describe how. (2) (Total 7 marks) Page 8

9 Thnton College M.(a) Marks awarded f this answer will be determined by the Quality of Communication (QC) as well as the standard of the scientific response. Examiners should also refer to the infmation in the Marking guidance and apply a best-fit approach to the marking. 0 marks No relevant content. Level ( 2 marks) The method described is weak and could not be used to collect valid results, however does show some understanding of the sequence of an investigation. Level 2 (3 4 marks) The method described could be followed and would enable some valid results to be collected, but lacks detail. Level 3 (5 6 marks) The method described could be easily followed and would enable valid results to be collected. Examples of the points made in the response: bean seedlings of same age cut material from same part of each gan (f repeats) e.g. top cm of stem / a whole cotyledon / seed equal mass of each gan accept weight f mass grind / homogenise in equal amounts of water / buffer equal volumes of hydrogen peroxide solution equal concentrations of hydrogen peroxide solution same temperature temperature maintained in water bath quantitative measure of gas production eg height of foam in mm / collect gas in graduated syringe in cm 3 f same time period repetitions (3+ times) calculate mean f each. 6 (b) (i) crect answer: 40 mark f 45 as the anomalous result has been included in the calculation mark f 2 (ii) vertical axis crectly labelled: Page 9

10 Enzyme activity in arbitrary units allow ecf from (b)(i) points plotted crectly ± mm deduct mark f each increct plot suitable line of best fit not feathery, not point to point Thnton College 2 (iii) 6.0 / 6 allow ± 0. if 6.0 not given, allow crect f candidate s graph ± 0. (iv) in range 0 to 4 units allow crect f candidate s graph (v) enzyme denatured / enzyme (active site) shape changed allow substrate no longer fits (active site) igne reference to temperature do not allow enzyme dies [5] M2.(a) (i) glycerol (ii) pancreas / small intestine accept duodenum / ileum igne intestine unqualified (b) any two from: type of milk volume / amount of milk vol. bile equals vol. water volume of lipase concentration of lipase temperature igne time interval igne solution unqualified do not allow ph Page 0

11 igne starting ph igne volume / amount of bile / water igne concentration of bile accept amount of lipase if neither volume n concentration given Thnton College 2 (c) (i) fatty acid (production) (ii) faster reaction / digestion (with bile) ph decreases faster (with bile) takes less time (with bile) steeper fall / line (with bile) allow use of data igne easier (iii) all fat / milk digested same amount of fatty acids present (lower ph) denatures the enzyme / lipase allow all reactants used up igne reference to neutralisation allow enzyme won t wk at low ph do not allow enzyme killed [7] M3.(a) stomach is acidic / has low ph allow any ph below 7 igne stomach is not alkaline lactase wks best / well in alkali / high ph / neutral / non-acidic conditions allow any ph of 7 and above accept wks slowly in acid conditions allow figures from table with a comparison igne reference to temperature Page

12 Thnton College (b) any three from: (below 40( C)) increase in temperature increases rate / speed of reaction reference to molecules moving faster / colliding faster / harder / me collisions enzyme optimum / wks best at 40 C allow value(s) in range igne body temperature unless qualified high temperatures (above 40 C) / 45 C / 50 C enzyme denatured allow synonyms f denaturation, but do not allow killed denaturation at high and low temperature does not gain this mark igne references to time / ph 3 (c) any two from: acid neutralised conditions made neutral / alkali accept bile is alkaline (allow) emulsification / greater surface area (of lipid / fat) allow description of emulsification eg fat broken down / broken up into droplets do not accept idea of chemical breakdown lipase / enzymes (in small intestine) wk me effectively / better allow better f enzymes igne reference to other named enzymes 2 [7] Page 2