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1. (a) is a diagram of the digestive system.
Each letter may be used once, more than once or not at all. State the letter of the part shown in Fig. 1.1:
that produces bile ..........................................
that produces gastric juice .............................
that produces urea .........................................
where maltose is digested .............................
where trypsin acts. .........................................
[5]
(b) A student investigated the effect of bile on the digestion of fat in milk. They set up three different test tubes:
- test-tube A contained milk and bile
- test-tube B contained milk and lipase
- test-tube C contained milk, lipase and bile.
They used an indicator that is pink in alkaline solutions and colourless in acidic solutions. They added the same volume of indicator to each test-tube. The student observed and recorded the colour of the contents of each test-tube at 0 minutes, 20 minutes and 40 minutes. [Table_1]
(i) Explain the results for test-tubes B and C in Table 1.1.
[4]
(ii) Explain the purpose of test-tube A in Table 1.1.
[2]
(c) The action of lipase is affected by temperature.
shows the axes for a graph of the effect of temperature on the activity of lipase. Complete the graph by:
- drawing a line to show the expected effect of temperature on the activity of lipase
- adding a label line and a label to show the point at which all the lipase has been denatured.
[2]
(d) Explain why lipase cannot be used to catalyse the breakdown of proteins.
[3]
577
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582
2. (a) A student investigated osmosis in potato plant cells. He immersed cubes of potato tissue in water and different concentrations of sucrose solution for 30 minutes. The masses of the potato cubes were measured before and after immersion. The percentage changes in mass were calculated. [Table_2]
(i) Using the information in Table 2.1, calculate the percentage change in mass at 1.00 mol dm–3. Give your answer to two decimal places.
[3]
(ii) Using the information in Table 2.1, explain the difference in the results between the 0.6 mol dm–3 and the 0.8 mol dm–3 sucrose solutions. Use the term water potential in your answer.
[5]
(iii) Describe the expected appearance of a cell from a potato cube that has been immersed in distilled water for 30 minutes.
[2]
(b) Describe how the process of active transport differs from the process of osmosis.
[3]
(c) State the type of plant cells that use active transport to absorb mineral ions from the environment.
[1]
(d) Explain the effect of a lack of magnesium ions on the colour of plant leaves.
[2]
537
502
558
3. (a) is a photomicrograph of some cells lining the trachea.
(i) Describe the role of goblet cells.
[2]
(ii) Explain how the cell labelled X in Fig. 3.1 is adapted for its function.
[2]
(iii) State the name of one other part of the body where the type of cell labelled X in Fig. 3.1 is found.
[1]
(b) [Table_3] contains some features of the breathing system. Complete Table 3.1 to show the actions of each feature of the breathing system that occur to cause inspiration.
[5]
(c) State the name of the gas that is excreted by the breathing system.
[1]
(d) Good ventilation is one feature of gas exchange surfaces. State two other features.
[2]
(e) State the name of the gas exchange surface in humans.
[1]
503
591
527
4. (a) shows the effect of light intensity on the rate of photosynthesis at different temperatures and concentrations of carbon dioxide. Describe and explain the reasons for the shape of lines B and C in Fig. 4.1.
[6]
(b) C6H12O6 is one of the products of photosynthesis. State the chemical formula of the other product.
[1]
(c) Outline how the carbohydrates made during photosynthesis are used in plants.
[4]
507
576
542
5. (a) shows the stages involved in protein synthesis. State the names of the parts labelled X, Y and Z in Fig. 5.1.
[3]
(ii) State what determines the sequence of the amino acids in the protein that is produced.
[1]
(iii) Explain why the sequence of amino acids is important in the production of receptor molecules for neurotransmitters.
[2]
(b) Explain why body cells can have different specialised functions even though they contain the same genes.
[2]
(c) Allele frequency in a population can be changed by natural selection and artificial selection. State the meaning of the term allele.
[1]
(d) Describe how artificial selection differs from natural selection.
[3]
(e) Mutation causes formation of new alleles which increases genetic variation. State two other sources of genetic variation in populations.
[2]
549
599
542
6. (a) A scientist monitored the changes in the pH in muscles before, during and after two minutes of vigorous exercise. The changes in pH are caused by the production of lactic acid. Complete the sentences to describe and explain the results in Fig. 6.1.
The pH decreases from ............................................... to ............................................... during vigorous exercise.
There is not enough ............................................... supplied to the muscles.
The body respires anaerobically. The lactic acid produced builds up in the muscles causing an ............................................... debt.
It takes ............................................... minutes for the muscle pH to return to its initial level after exercise.
The pH value increases after vigorous exercise has ended, as lactic acid is transported in the ............................................... to the ............................................... .
During this time the breathing rate and ............................................... rate remain high.
[6]
(b) Yeast can respire anaerobically.
(i) Complete the balanced chemical equation for anaerobic respiration in yeast. C6H12O6 ......................................................................................................................
[2]
(ii) Yeast belongs to the kingdom fungus. State one cell component that is present in yeast cells but is absent in animal cells.
[1]
563
501
588
