... (1) Scientists compared the performance of this new detergent with an existing detergent.

Transcription

1 Enzymes (Higher) 5 minutes 5 marks Q. Enzymes are used in biological detergents. (a) Name the type of enzyme that digests stains containing fats () (b) A new detergent is marketed as being environmentally-friendly. Scientists compared the performance of this new detergent with an existing detergent. They measured the time taken by the two detergents to remove a fat stain at different temperatures. The graph shows their results. (i) Describe the effect of increasing the temperature on the time taken by the existing detergent to remove the stain.

2 The new detergent works at a lower temperature than the existing one. Is the new detergent likely to be more environmentally-friendly than the existing detergent? Draw a ring around your answer. Yes / No Explain the reason for your answer. (c) Neither detergent works well at 60 C. Explain why (Total 7 marks) Q. The diagram shows the apparatus used to investigate the digestion of milk fat by an enzyme. The reaction mixture contained milk and the enzyme. In Experiment, bile was also added. In Experiment, an equal volume of water replaced the bile. In each experiment, the ph was recorded at minute intervals.

3 The results of the two experiments are given in the table. Time in minutes Experiment : with bile ph Experiment : without bile (a) Milk fat is a type of lipid. Explain why the ph changed in experiment (b) (i) For Experiment, calculate the average rate of fall in ph per minute, between 4 minutes and 8 minutes. Show clearly how you work out your final answer ph units per minute The average rate of fall in ph per minute for Experiment was 0. units of ph per minute. Explain the difference in the rate of fall in ph when bile is present () (Total 5 marks)

4 Q3. The diagram shows the apparatus used to investigate the digestion of milk fat by an enzyme. The reaction mixture contained milk, sodium carbonate solution (an alkali) and the enzyme. In Experiment, bile was also added. In Experiment, an equal volume of water replaced the bile. In each experiment, the ph was recorded at -minute intervals. Either: Experiment or: Experiment milk (contains fat) sodium carbonate solution bile enzyme milk (contains fat) sodium carbonate solution water enzyme The results of the two experiments are given in the table.

5 (a) Milk fat is a type of lipid. Give the name of an enzyme which catalyses the breakdown of lipids () (b) What was produced in each experiment to cause the fall in ph?..... () (c) (i) For Experiment, calculate the average rate of fall in ph per minute, between 4 minutes and 8 minutes. Show clearly how you work out your final answer.... ph units per minute Why was the fall in ph faster when bile was present? () (Total 5 marks) Q4. A manufacturer of slimming foods is investigating the effectiveness of carbohydrases from different microorganisms. Iodine solution is a pale golden brown, transparent solution. Starch reacts with iodine to form a dark blue mixture. Known concentrations of starch are added to iodine solution. The mixture is placed in a colorimeter which measures the percentage of light passing through the mixture.

6 Graph shows the results. (a) Explain why less light passes through the mixture when the starch is more concentrated () (b) The manufacturer adds carbohydrase from each of three different microorganisms, A, Band C, to starch in flasks at 40 C. Every minute a sample of the mixture is added to iodine solution and placed in the colorimeter. Graph shows these results.

7 (i) When the concentration of starch reaches %, digestion is considered to be sufficient for the next stage in the manufacture of the slimming food. How long does this take for the most effective carbohydrase? Show clearly how you work out your answer.... minutes Explain why the manufacturer carried out the investigation at 40 C. (c) Carbohydrases convert starch into glucose. To complete the manufacture of the slimming food the glucose should be converted into fructose. (i) Name the enzyme which would be used to convert glucose into fructose. () Explain why fructose, rather than glucose, is used in slimming foods. (Total 8 marks)

8 M. (a) lipase allow phonetic spelling allow lipidase (b) (i) fall then rise owtte eg down then up allow faster then slower ignore explanations minimum / least / fastest / best / optimum at 39 4( C) allow it falls to 40( C) if no other marks gained, falls to an optimum gains mark (yes) there is no mark for circling yes maximum mark if No is circled any two from: less heat / energy / electricity / power required /used / wasted ignore lower temperature conserves fuel suppliesor less fuel used less pollution from power stationsowtte accept less global warming or less CO / carbon emissions / greenhouse gases or less SO / acid rain NB only direct effects less pollution only is not enough (c) any two from: max mark for reference to cell enzyme / lipase accept any named enzyme destroyed / denatured allow damaged / broken down not killed reference to (specific) shape changed ignore detergent / it [7]

9 M. (a) the enzyme must be lipase since fatty acid produced, which lowered the ph (b) (i) 0.5 or correct answer with / without working if answer incorrect / missing, then evidence of gains mark bile provides optimum / suitable / best ph for enzyme action therefore the rate of the reaction increased [5] M3. (a) lipase (b) fatty acid ignore glycerol (c) (i) 0.5 or if correct answer ignore working or lack of working for mark fats emulsified or described re. Small droplets or large S.A. (for enzyme action) or fats mix better with water do not allow breakdown / breakup unqualified [5] M4. (a) opaque / less transparent / blue allow mixture becomes dark / black

10 ignore thicker (b) (i) 7 (minutes) or in range 6.7 to 7 award marks for correct answer if answer is incorrect evidence of selection of40(% light intensity) either in working or in graph for mark any two from: slower / takes longer at lower temperatures (40 o C is) optimum / best temperature allow near to 37 o C / body temperature where enzymes work best enzyme denatured / destroyed / damaged at higher temperatures allow description of denaturation (c) (i) isomerase allow phonetic spelling fructose is sweeter than glucose needed in smallerquantities or less is needed [8]