12. Energy and respiration
A section of Biology, 9700
Listing 10 of 192 questions
All cells need ATP for energy-requiring processes in the body. shows the molecular structure of ATP. O– O O– P O O O– P O O O O O– P OH OH Y X N N N N H2N Name the base labelled X. Name the sugar labelled Y. State three reasons why ATP is ideal as an energy currency in all living organisms. ATP is produced in three stages of aerobic respiration. Complete the table below to show two products of each stage, other than ATP. stage products glycolysis 1. 2. Krebs cycle 1. 2. oxidative phosphorylation 1. 2. Carbohydrates and lipids are both used as respiratory substrates. Table 7.1 shows the energy values of carbohydrates and lipids. Table 7.1 respiratory substrate energy value / kJ g−1 carbohydrate 15.8 lipid 39.4 Explain why lipids have a higher energy value than carbohydrates. Respiration can be investigated by calculating the respiratory quotient (RQ). State how the RQ is calculated. Give the typical RQ values obtained from the respiration of carbohydrates and lipids. carbohydrate lipid Suggest what happens to the RQ value when respiration in yeast becomes anaerobic.
9700_s15_qp_42
THEORY
2015
Paper 4, Variant 2
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At the end of glycolysis in mammalian muscle tissue, pyruvate is formed. Pyruvate can be further metabolised along two different pathways, pathway 1 and pathway 2. outlines the two pathways. pyruvate acetyl CoA lactate pathway 1 pathway 2 NAD reduced NAD reduced NAD NAD X State the condition under which pyruvate would be metabolised along pathway 2. Name compound X. Name the two types of reaction that are involved in pathway 1. Suggest a cell in a mammal that cannot carry out pathway 1. Give a reason for your answer. ATP is synthesised during glycolysis. Name the process by which ATP is synthesised. The rufous hummingbird, Selasphorus rufus, feeds on the nectar produced by flowers. Nectar is a liquid containing sugars. Hummingbirds hover to maintain a position next to a flower while they feed. This requires a lot of energy. is a rufous hummingbird. Hummingbirds that have not fed for some time have a respiratory quotient (RQ) value of 0.7. After feeding their RQ value is 1.0. Define the term respiratory quotient. Explain why a hummingbird that has not fed for some time has an RQ value of 0.7, while a hummingbird that has fed has an RQ value of 1.0. When animals exercise they can respire substrates obtained directly from their diet, as well as respiring substrates from energy stores. An investigation worked out the percentage of respiration that used substrates obtained directly from the diet of humans and hummingbirds as they exercised. shows the results of this investigation. human hummingbird percentage of respiration that used substrates obtained directly from the diet animal shows that hummingbirds have a higher percentage of respiration that uses substrates obtained directly from the diet. Calculate how many times greater this figure is for hummingbirds compared to humans. Show your working and write your answer to two decimal places. answer = Suggest the benefits to a hummingbird of obtaining most of its respiratory substrates from its diet while exercising.
9700_s20_qp_41
THEORY
2020
Paper 4, Variant 1
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shows part of the process of respiration in a mitochondrion. ETC A D C B NAD reduced NAD Krebs cycle water ATP ADP + Pi e– e– H+ H+ H+ H+ With reference to , name: area A process B substance C State the type of chemical compound that is represented by D. State the process by which ATP can be synthesised directly during glycolysis or the Krebs cycle. The elephant seal, Mirounga angustirostris, spends most of its life in the ocean. is an elephant seal. Elephant seals can stay underwater for up to two hours. During this time, respiration continues. shows the mass of blood in the body, as a percentage of total body mass, for the elephant seal and for three other mammals. elephant seal mass of blood as a percentage of total body mass dog mammal human cow shows that elephant seals have a higher mass of blood as a percentage of total body mass than humans. Calculate how many times greater this figure is for elephant seals compared to humans. Show your working and write your answer to two decimal places. answer Suggest why an elephant seal needs such a large mass of blood as a percentage of total body mass. Elephant seals have a very thick layer of adipose tissue under their skin. Adipose cells are rich in fat molecules. Suggest why 1 g of fat will produce more ATP than 1 g of carbohydrate as a respiratory substrate in aerobic respiration. Adipose tissue plays an important role in thermoregulation in elephant seals. State the role of adipose tissue in thermoregulation. The hypothalamus in the brain is the control centre for thermoregulation. Outline how a change in temperature of the external environment results in an impulse arriving at the hypothalamus. When the blood temperature of a mammal decreases, one response is that its body secretes more adrenaline. Suggest how an increase in adrenaline results in an increase in blood temperature.
9700_s20_qp_43
THEORY
2020
Paper 4, Variant 3
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Outline the role of oxygen in aerobic respiration. Table 3.1 shows the results of some measurements of the energy released by different respiratory substrates and the water produced in the process. Table 3.1 respiratory substrate energy released / kJ mass of water produced / g per g of substrate per dm3 of oxygen consumed per g of substrate carbohydrate 17.4 20.9 0.56 lipid 39.3 19.6 1.07 protein 17.8 18.6 0.45 Describe and explain the differences in energy released by the three respiratory substrates. Suggest why more water is produced from the metabolism of lipid than from the other two substrates.
9700_w13_qp_43
THEORY
2013
Paper 4, Variant 3
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The respiratory quotient (RQ) values for different respiratory substrates can be calculated. Table 5.1 shows: • the formulae of four respiratory substrates • the number of oxygen molecules (O2) needed to completely respire each substrate to carbon dioxide and water. Table 5.1 respiratory substrate formula number of oxygen molecules needed for respiration beta-hydroxybutyric acid C4H8O3 4.5 glucose C6H12O6 6.0 malic acid C4H6O5 3.0 oleic acid C18H34O2 25.5 Using Table 5.1, name the respiratory substrate with the highest RQ and the respiratory substrate with the lowest RQ. respiratory substrate with the highest RQ respiratory substrate with the lowest RQ In anaerobic conditions, the production of ATP in mammals and yeast involves glycolysis and fermentation. Describe the similarities and differences between fermentation in mammals and in yeast.
9700_w23_qp_41
THEORY
2023
Paper 4, Variant 1
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The respiratory quotient (RQ) values for different respiratory substrates can be calculated. Table 5.1 shows: • the formulae of four respiratory substrates • the number of oxygen molecules (O2) needed to completely respire each substrate to carbon dioxide and water. Table 5.1 respiratory substrate formula number of oxygen molecules needed for respiration beta-hydroxybutyric acid C4H8O3 4.5 glucose C6H12O6 6.0 malic acid C4H6O5 3.0 oleic acid C18H34O2 25.5 Using Table 5.1, name the respiratory substrate with the highest RQ and the respiratory substrate with the lowest RQ. respiratory substrate with the highest RQ respiratory substrate with the lowest RQ In anaerobic conditions, the production of ATP in mammals and yeast involves glycolysis and fermentation. Describe the similarities and differences between fermentation in mammals and in yeast.
9700_w23_qp_43
THEORY
2023
Paper 4, Variant 3
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Questions Discovered
192