A-level Biology (7401/7402)
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- Bu səhifədəki naviqasiya:
- Hamster age group Number of hamsters in group
- Fast fibres (± SD) Young
- Time / minutes Total volume of gas collected / cm 3
(2) (Total 8 marks) Q7. A scientist investigated the uptake of radioactively labelled carbon dioxide in chloroplasts. She used three tubes, each containing different components of chloroplasts. She measured the uptake of carbon dioxide in each of these tubes. Her results are shown in the table.
(a) Name the substance which combines with carbon dioxide in a chloroplast. ........................................................................................................................
(b) Explain why the results in tube B are similar to those in tube A. ........................................................................................................................ ........................................................................................................................ ........................................................................................................................
(c) Use the information in the table to predict the uptake of radioactively labelled carbon dioxide if tube A was placed in the dark. Explain your answer. ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................
(d) Use your knowledge of the light-independent reaction to explain why the uptake of carbon dioxide in tube C was less than the uptake in tube B. ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................
(e) DCMU is used as a weed killer. It inhibits electron transfer during photosynthesis. The addition of DCMU to tube A decreased the uptake of carbon dioxide. Explain why. ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................
Q8. (a) A student investigated the effect of pH on the activity of the enzyme amylase. She set up the apparatus shown in the diagram.
The tubes were made from Visking tubing. Visking tubing is partially permeable. She added an equal volume of amylase solution and starch to each tube. • She added a buffer solution at pH2 to tube A. • She added an equal volume of buffer solution at pH8 to tube B. After 30 minutes, she measured the height of the solutions in both tubes. She then tested the solutions in tubes A and B for the presence of reducing sugars. Describe how the student would show that reducing sugars were present in a solution. ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ (Extra space) ................................................................................................. ........................................................................................................................ ........................................................................................................................
(b) After 30 minutes, the solution in tube B was higher than the solution in tube A. (i) Explain why the solution in tube B was higher. ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... ...............................................................................................................
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(ii) The student concluded from her investigation that the optimum pH of amylase was pH8. Is this conclusion valid? Explain your answer ............................................................................................................... ............................................................................................................... ...............................................................................................................
Q9.Researchers investigated whether the blood supply to slow and fast muscle fibres in a muscle changes with age. They used diaphragms taken from hamsters (Mesocricetus auratus). The diaphragm is in constant use for breathing. They took diaphragms from groups of young, adult and old hamsters. They removed the diaphragm from each animal and took a sample of muscle tissue.They examined it under an optical (light) microscope. For each sample they selected several fields of view at random. In each field of view, they then counted the number of capillaries associated with each type of muscle fibre. This allowed the researchers to calculate the mean number of capillaries for each type of muscle fibre, for each age group. The table below shows the researchers’ results which include standard deviation (SD).
(a) Give four precautions that the researchers took to make their calculations of mean number of capillaries per fibre reliable. 1 ..................................................................................................................... ........................................................................................................................ 2 ..................................................................................................................... ........................................................................................................................ 3 ..................................................................................................................... ........................................................................................................................ 4 ..................................................................................................................... ........................................................................................................................ (4) (b) The researchers examined the muscle of an animal in the old age group. They found one field of view containing only slow muscle fibres. They counted 69 capillaries in this field of view. (i) Use a calculation to estimate how many slow muscle fibres were visible in this field of view. Show your working.
Number of slow muscle fibres = .......................................................... (2) (ii) The actual number of slow muscle fibres in the field of view was not the same as the number you calculated in question (i). Give one reason why. ............................................................................................................... ............................................................................................................... ............................................................................................................... (1) (c) A student read the report of the researchers’ investigation. She thought that the investigation was unethical but that a conclusion could still be made. (i) Suggest why she thought the investigation was unethical. ............................................................................................................... ............................................................................................................... ............................................................................................................... (1) (ii) She concluded that age had a significant effect on the mean number of capillaries per fibre. Evaluate this conclusion. ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... ...............................................................................................................
(a) Describe how the students would have returned the air bubble to the start of the capillary tube in this investigation. ........................................................................................................................ ........................................................................................................................ ........................................................................................................................
(b) Give two precautions the students should have taken when setting up the potometer to obtain reliable measurements of water uptake by the plant shoot. 1...................................................................................................................... 2...................................................................................................................... (2) (c) A potometer measures the rate of water uptake rather than the rate of transpiration. Give two reasons why the potometer does not truly measure the rate of transpiration. 1...................................................................................................................... 2...................................................................................................................... (2) (d) The students’ results are shown in the table.
Explain the relationship between the number of leaves removed from the plant shoot and the mean rate of water uptake. ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ (Extra space).................................................................................................. ........................................................................................................................ ........................................................................................................................
(a) Explain why a layer of oil is required in this investigation. ........................................................................................................................ ........................................................................................................................ (1) (b) The student’s results are shown in the following table.
(i) Calculate the rate of gas production in cm3 g–1 min–1 during the first 40 minutes of this investigation. Show your working.
Answer = ................... cm3 g–1 min–1 (2) (ii) Suggest why the rate of gas production decreased between 50 and 60 minutes. ............................................................................................................... ............................................................................................................... (1) (iii) Yeast can also respire aerobically. The student repeated the investigation with a fresh sample of yeast in glucose solution, but without the oil. All other conditions remained the same. Explain what would happen to the volume of gas in the syringe if the yeast were only respiring aerobically. ............................................................................................................... ............................................................................................................... ............................................................................................................... ...............................................................................................................
(c) Respiration produces more ATP per molecule of glucose in the presence of oxygen than it does when oxygen is absent. Explain why. ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ (2) (Total 8 marks) Q12.Some mice have diabetes. The diabetes causes the blood glucose concentration to become very high after a meal. Scientists investigated the use of an inhibitor of amylase to treat diabetes. The scientists took 30 mice with diabetes and divided them into two groups, A and B. • Group A was given yoghurt without the inhibitor of amylase each day. • Group B was given yoghurt with the inhibitor of amylase each day. Apart from the yoghurt, all of the mice were given the same food each day. The scientists measured the blood glucose concentration of each mouse, 1 hour after it had eaten. This was done on days 1, 10 and 20 after the investigation started. The following figure shows the scientists’ results.
(a) Group A acted as a control in this investigation. Explain the purpose of this group. ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ Yüklə 294,43 Kb. Dostları ilə paylaş:
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