B2.5 Proteins– their functions and uses Version 2.0 Copyright © AQA and its licensors. All rights reserved.

The diagram shows the human digestive system B2.5 Proteins– their functions and uses BL2FP June 2012 The diagram shows the human digestive system Heartburn is a burning feeling caused when acid enters the oesophagus. The acid comes from the stomach. (i) Which letter on the diagram shows the stomach? (1 mark) (ii) Name the acid the stomach produces. (1 mark) (iii) Medicines taken to treat heartburn contain chemicals that neutralise excess stomach acid. What type of chemical will neutralise stomach acid? (1 mark) Version 2.0 Copyright © AQA and its licensors. All rights reserved.

………………………………………………………………………………………………………. B2.5 Proteins– their functions and uses BL2FP June 2012 (b) Use words from the box and your own knowledge to describe how carbohydrates are digested. ………………………………………………………………………………………………………. ……………………………………………………………………………………………………….. ( 5 marks) (c) Where in the body are the products of digestion absorbed? ................................................................................................................. (1 mark) Version 2.0 Copyright © AQA and its licensors. All rights reserved.

B2.5 Proteins– their functions and uses BL2FP June 2012 mark scheme Version 2.0 Copyright © AQA and its licensors. All rights reserved.

Exampro QSP 2H 08 8 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 1, bile was also added. In Experiment 2, an equal volume of water replaced the bile. In each experiment, the pH was recorded at 2 minute intervals. Version 2.0 Copyright © AQA and its licensors. All rights reserved.

Experiment 2: without bile The results of the two experiments are given in the table. Time in minutes pH Experiment 1: with bile Experiment 2: without bile 9.0 2 8.8 4 8.7 6 8.1 8 7.7 8.6 10 7.6 8.2 8 (a) Milk fat is a type of lipid. Explain why the pH changed in experiment 2.   …………………………………………………………………………………………………………………………………….. …………………………………………………………………………………………………………………………………….. ……………………………………………………………………………………………............................................... …………………………………………………………………………………………….............................................. (2 marks) . Version 2.0 Copyright © AQA and its licensors. All rights reserved.

Show clearly how you work out your final answer. 8 (b) (i) For Experiment 1, 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 (2 marks) 8 (b) (ii) The average rate of fall in pH per minute for Experiment 2 was 0.1 units of pH per minute.   Explain the difference in the rate of fall in pH when bile is present. (1 mark) Version 2.0 Copyright © AQA and its licensors. All rights reserved.

answers extra information 8(a) 1 1 8(b)(i) 8(b)(ii) 1 5 question answers extra information mark 8(a) the enzyme must be lipase since fatty acid produced, which lowered the pH   1 1 8(b)(i) 0.25 or correct answer with / without working if answer incorrect / missing, then evidence of gains 1 mark 8(b)(ii) bile provides optimum / suitable / best pH for enzyme action therefore the rate of the reaction increased 1 Total 5 Version 2.0 Copyright © AQA and its licensors. All rights reserved.

Exampro Q08s 2H 07 1 Enzymes are used in biological detergents. 1 (a) Name the type of enzyme that digests stains containing fats. ............................................................................................................................................. (1 mark) 1 (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. Version 2.0 Copyright © AQA and its licensors. All rights reserved.

existing detergent to remove the stain. 1 (b) (i) Describe the effect of increasing the temperature on the time taken by the existing detergent to remove the stain. …………………………………………………………………………………………………………………………………….. ……………………………………………………………………………………………............................................... (2 marks) 1 (b) (ii) 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. Version 2.0 Copyright © AQA and its licensors. All rights reserved.

1 (c) Neither detergent works well at 60 °C. Explain why. …………………………………………………………………………………………………………………………………….. ……………………………………………………………………………………………............................................... (2 marks) Version 2.0 Copyright © AQA and its licensors. All rights reserved.

Version 2.0 Copyright © AQA and its licensors. All rights reserved.

Version 2.0 Copyright © AQA and its licensors. All rights reserved.