1. 2. Explain the process of aerobic cellular respiration.
1. Explain the process of aerobic cellular respiration. (Total 8 marks) 2. At the start of glycolysis, glucose is phosphorylated to produce glucose 6-phosphate, which is converted into fructose 6-phosphate. A second phosphorylation reaction is then carried out, in which fructose 6-phosphate is converted into fructose 1,6-bisphosphate. This reaction is catalyzed by the enzyme phosphofructokinase. Biochemists measured the enzyme activity of phosphofructokinase (the rate at which it catalyzed the reaction) at different concentrations of fructose 6-phosphate. The enzyme activity was measured with a low concentration of ATP and a high concentration of ATP in the reaction mixture. The graph below shows the results. Low ATP concentration Enzyme activity High ATP concentration Fructose 6-phosphate concentration (a) (i) Using only the data in the above graph, outline the effect of increasing fructose 6-phosphate concentration on the activity of phosphofructokinase, at a low ATP concentration. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... (2) 1 (ii) Explain how increases in fructose 6-phosphate concentration affect the activity of the enzyme. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... (2) (b) (i) Outline the effect of increasing the ATP concentration on the activity of phosphofructokinase. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... (2) (ii) Suggest an advantage to living organisms of the effect of ATP on phosphofructokinase. ........................................................................................................................... ........................................................................................................................... (1) (Total 7 marks) 2 3. Up to two additional marks are available for the construction of your answers. (2) (a) Draw and label a mitochondrion as seen in electron micrographs. (4) (b) Outline the cellular locations of different named processes in both photosynthesis and cell respiration. (6) (c) Explain the energy flow in a food chain as exemplified by a pyramid of energy. (8) (Total 20 marks) 4. The respiratory quotient (RQ) is a measure of the metabolic activity of an animal. It is the ratio of CO2 produced to O2 consumed. In general, the lower the RQ value the higher the energy yield. The RQ is dependent on the diet consumed by the animal. The following table lists the typical RQ values for specified diets. Diet RQ Lipid 0.71 Carbohydrate 1.00 Protein 0.74 [Source: Walsberg and Wolf, Journal of Experimental Biology, (1995), 198, pages 213–219. Reproduced by permission of The Company of Biologists Ltd] In an experiment to assess RQ values for house sparrows, the birds were fed a diet of pure mealworms (beetle larvae) or millet (a type of grain). 3 The graph below shows the RQ values of a house sparrow fed on a high carbohydrate diet (millet) and a high lipid diet (mealworms). 1.0 Key: Millet Mealworms Respiratory quotient 0.9 0.8 0.7 0.6 0 1 5 3 2 4 Time after feeding / h 6 7 [Source: Walsberg and Wolf, Journal of Experimental Biology, (1995), 198, pages 213–219. Reproduced by permission of The Company of Biologists Ltd] (a) Compare the RQ values for millet and mealworms between 1 hour and 6 hours after feeding. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (2) The expected RQ value for house sparrows metabolizing millet is 0.93. The expected value when metabolizing mealworms is 0.75. 4 (b) Explain why the expected RQ values for millet and mealworms are different. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (2) (c) Suggest reasons for (i) the high initial RQ values for house sparrows fed on millet; ........................................................................................................................... ........................................................................................................................... (1) (ii) the rapid fall in RQ values for house sparrows fed on millet. ........................................................................................................................... ........................................................................................................................... (1) (Total 6 marks) 5. Explain the similarities and differences in anaerobic and aerobic cellular respiration. (Total 8 marks) 5 6. The mitochondrion carries out key reactions in the cells of eukaryotes. A B [Source: D S Friend, Brigham and Women’s Hospital, www.nigms.nih.gov/ news/science_ed/mito1.html] (a) (i) State the name of label A and label B in the photomicrograph above. A: ............................................................................................................... B: ............................................................................................................... (1) (ii) State the processes that occur at label A and label B. A: ............................................................................................................... B: ............................................................................................................... (1) 6 (b) Explain the relationship between the structure of the mitochondrion and its function. ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... (3) (Total 5 marks) 7. Explain the process of aerobic respiration including oxidative phosphorylation. (Total 8 marks) 8. (a) Photosynthesis consists of two sets of reactions. State the names of these two sets. ...................................................................................................................................... ...................................................................................................................................... (1) (b) Outline how one specific limiting factor affects the rate of photosynthesis. ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... (2) 7 (c) Explain the production of ATP by chemiosmosis during photosynthesis. ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... (3) (Total 6 marks) 9. (a) State two products of the process of glycolysis. ..................................................................................................................................... ..................................................................................................................................... (1) (b) Explain the significance of polar and non-polar amino acids within the cell. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (3) (Total 4 marks) 8 10. (a) State two functions of proteins with a named example of each. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (2) (b) Explain chemiosmosis as it occurs during cell respiration. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (2) (Total 4 marks) 9 11. The electron micrographs below show mitochondria in longitudinal section. The mitochondrion in A is from a bat pancreas cell and that in B is from a mouse liver cell. A. B. [Source: Tribe and Whittaker, Chloroplasts and Mitochondria, (1972), 31, pp 28–29] (a) Annotate the micrographs to show two similarities in the structure of the mitochondria. (2) (b) The mitochondria differ in size. State two other differences that are visible in the mitochondria. 1. .......................................................................................................................... 2. .......................................................................................................................... (2) 10 (c) Predict, with two reasons, which of the mitochondria would have been able to produce ATP at a greater rate. .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... (3) (Total 7 marks) 12. (a) (i) Identify the cell organelle shown in the micrograph below. ........................................................................................................................... (1) 11 (ii) Identify the structure labelled I above and explain how it is adapted for the organelle to function efficiently. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... (3) (b) Describe the role of acetyl CoA in the metabolism of lipids. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (2) (Total 6 marks) 13. Anaerobic respiration occurs in the absence of oxygen while aerobic respiration requires oxygen. (a) State one final product of anaerobic respiration. ..................................................................................................................................... (1) 12 (b) Complete the table showing the differences between oxidation and reduction. Oxidation Reduction Electrons gained or lost Oxygen or hydrogen gained or lost (2) (c) The structure of a mitochondrion is shown in the electron micrograph below. Name the parts labelled A, B and C and state the function of each. Part A: Name: .......................................................................................................... Function: ...................................................................................................... Part B: Name: ........................................................................................................... Function: ...................................................................................................... Part C: Name: ........................................................................................................... Function: ...................................................................................................... (3) (Total 6 marks) 13 14. Studies have been carried out on the consumption of oxygen by mammals under different conditions. The graph below shows the oxygen consumption of a pigmy possum (Cercaertus nanus) at various air temperatures. 5 4 Oxygen consumption / ml O 2 g - 1 h - 1 3 2 1 0 0 5 10 15 20 25 Air temperature / C 30 35 40 Knut Schmidt-Nielsen, Animal Physiology, Adaptation and Environment, 5ed (Cambridge: Cambridge University Press, 1997). Reprinted with permission. (a) Estimate the oxygen consumption at 20C. .................................................................................................................................... (1) (b) Outline the effect of temperature on oxygen consumption. .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... (2) 14 (c) An air temperature of 32C is the lower critical temperature for a pigmy possum. Deduce the meaning of lower critical temperature. .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... (1) The graph below shows the metabolic rates of various mammals in relation to air temperatures. Metabolic rate refers to the rate of use of energy by an animal and may be measured indirectly by oxygen consumption. The basal metabolic rate (BMR) for each animal, in the absence of stress, is given the value of 100. This occurs at different temperatures for different animals. The changes in metabolic rate as the temperature falls are expressed as a percentage of the BMR for each animal. [Knut Schmidt-Nielsen, Animal Physiology, Adaptation and Environment, 5ed (Cambridge: Cambridge University Press, 1997). Reprinted with permission.] (d) (i) Identify the mammal with the greatest increase in metabolic rate per degree of temperature, as the temperature decreases. .......................................................................................................................... (1) 15 (ii) Calculate the average change in the metabolic rate, per degree of temperature, of a weasel as the temperature decreases from 17C to –20C. Show your workings. .......................................................................................................................... .......................................................................................................................... .......................................................................................................................... .......................................................................................................................... (2) (e) Suggest one reason for the increase in metabolic rate of mammals at lower temperatures. .................................................................................................................................... .................................................................................................................................... (1) (f) Discuss the differences between tropical and arctic mammals regarding the changes in their metabolic rates as the temperature decreases. .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... (3) 16 Other studies were carried out to see the relationship of the thickness of fur in mammals to its value as an insulator. A good insulator prevents heat loss from the animals to their environment. The graph below shows the relationship of the fur thickness to fur insulation in different mammals. Symbols represent the transfer of heat from fur to air or fur to ice water. 4.0 3.5 white fox 3.0 wolf grizzly bear polar bear red fox reindeer 2.5 rabbit Fur insulation value / W dm–2 dall sheep dog beaver 2.0 1.5 seal lemming squirrel 1.0 seal in ice water weasel 0.5 shrew beaver in ice water polar bear in ice water 0.0 0 10 20 30 40 50 60 70 80 Fur thickness / mm Key : ♦ = the rate of transfer of heat from fur to air ◊ = the rate of transfer of heat from fur to ice water [Source: K Schmidt-Nielsen, Animal Physiology, Adaptation and Environment, (1978), CUP, pp 321] (g) (i) Calculate the difference in fur thickness between a reindeer and a grizzly bear. .......................................................................................................................... .......................................................................................................................... (1) (ii) Suggest a reason for their similar fur insulation value. .......................................................................................................................... .......................................................................................................................... (1) 17 (h) (i) Calculate the change in the insulation value for a beaver when it enters ice water. .......................................................................................................................... .......................................................................................................................... (1) (ii) Suggest an adaptation that allows a mammal to maintain its body temperature while in ice water. .......................................................................................................................... .......................................................................................................................... (1) (i) Discuss the relationship between metabolic rate and fur thickness in mammals. .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... (3) (Total 18 marks) 18 15. The eastern oyster (Crassostrea virginica) is a marine mollusc that lives in estuaries. The environmental surroundings of the eastern oyster, such as the temperature and concentration of trace elements, are constantly changing. The trace element cadmium affects the mitochondria and prevents them from carrying out their function efficiently. Investigators isolated mitochondria from the oysters to study how the respiration rate changed while varying the water temperature and the cadmium ion concentration. 3.0 Key: 2.5 Respiration rate / arbitrary units 15 °C 25 °C 35 °C 1.5 1.0 0.5 0.0 0 1 5 10 15 Cadmium ion concentration / µ mol 20 dm–3 [Source: I M Sokolova, (2004), The Journal of Experimental Biology, 207, pages 2639–2648. With permission of the Company of Biologists Ltd.] (a) State the relationship between the concentration of cadmium ions and respiration rate at 35C. ..................................................................................................................................... ..................................................................................................................................... (1) (b) Compare the respiration rate of the mitochondria at cadmium ion concentrations of 0mol dm–3 and 50mol dm–3. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (2) 19 (c) Suggest one other environmental property of the water, apart from temperature and mineral concentration, that may show daily changes. ..................................................................................................................................... (1) (d) The investigators concluded that seasonal and global warming might make the eastern oysters more likely to suffer from trace element poisoning. Using the data, evaluate this hypothesis. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (3) (Total 7 marks) 20 Mitochondrial electron transport defects (called mitochondrial myopathy) causes tiredness at low levels of exercise and varies from mild to severe. Scientists measured oxygen delivery to cells and oxygen use in cells of thirty-five patients with mitochondrial myopathy. The results were compared to a control group of thirty-two healthy individuals. The results are shown in the two charts below. Oxygen delivery to cells Oxygen use in cells 400 50 45 350 40 Rate/ml Kg–1min –1 Rate/ml Kg–1min –1 16. 300 250 200 35 30 25 20 15 10 150 5 Key: mitochondrial myopathy group control group [Source: adapted from T. Taivassalo and R. G. Haller, (2006), ‘Exercise and training in mitochondrial myopathies’, Medicine and Science in Sports and Exercise, 37 (12) 2094-2101, © Lippincott Williams & Wilkins, USA] (a) State the mean value for oxygen delivery to cells in patients suffering from mitochondrial myopathy. ...................................................................................................................................... (1) (b) Calculate the percentage difference of the oxygen use in cells by the control group compared to oxygen use in cells of patients with mitochondrial myopathy. ................ % (1) 21 (c) Discuss why people with mitochondrial myopathy tire more easily than healthy individuals. ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... (3) (Total 5 marks) 17. The diagram below shows possible pathways for the breakdown of glucose in various cells. Glucose A Process Q (no oxygen present) B (a) C+D Process R (oxygen present) D+E State the names of processes Q and R. Q: ........................................................................................................................... (1) R: ........................................................................................................................... (1) (b) Deduce the names of substances A and D. A: ........................................................................................................................... (1) D: ........................................................................................................................... (1) 22 (c) State the organelle in which process R takes place. ..................................................................................................................................... (1) (Total 5 marks) 18. Fruits remain alive for a period of time after harvesting. Cellular respiration continues and it can greatly influence the maturation (ripening) process in the fruits. The rate of respiration depends on many factors such as the type, quality, degree of ripeness and water content of the fruits, temperature and air composition. Respiration that continues after harvesting may sometimes lead to the over-ripening and eventual loss of an entire cargo of fruit during transport. Studies of the maturation process in bananas are summarized in the following graph. Relative rate green green/yellow yellow Time/arbitrary units (showing colour changes in bananas) Key: chlorophyll breakdown starch breakdown water release CO 2 formation Sugar formation [Source: www.containerhandbuch.de/chb_e/scha/index.html?/chb_e/scha/scha_15_02_03_02.html] (a) (i) State two chemical products released as gases during cellular respiration. 1 ........................................................................................................................ 2 ........................................................................................................................ (1) (ii) State one non-chemical product of respiration. ........................................................................................................................... (1) (b) Using the data, analyse the events that occur when maturation begins in bananas. 23 ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (2) (c) Suggest, giving reasons, two ways in which transport conditions can be controlled to minimize over-ripening. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (2) (Total 6 marks) 24
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