12.2. Respiration
A subsection of Biology, 9700, through 12. Energy and respiration
Listing 10 of 158 questions
The molecules listed below are all associated with respiration. ATP synthase glucose ATP NAD oxaloacetate pyruvate citrate oxygen From these molecules identify: a phosphorylated nucleotide a 3-carbon compound a coenzyme an enzyme A sample of tree sap, rich in sugars, was found to be contaminated with yeast. This sample was tested for the concentration of ethanol at regular intervals. The results are shown in . ethanol concentration / arbitrary units time / hours Calculate the percentage increase in ethanol concentration between 15 and 45 hours. Show your working. answer % Suggest why the concentration of ethanol decreased after 45 hours.
9700_w15_qp_42
THEORY
2015
Paper 4, Variant 2
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In respiration, most ATP is synthesised during oxidative phosphorylation. Some ATP is made by substrate-linked reactions in glycolysis and Krebs cycle. Describe how ATP is made by substrate-linked reactions. Lipids can be metabolised to provide ATP. • The enzyme lipase hydrolyses lipids to glycerol and fatty acids. • The hydrocarbon chain of the fatty acid breaks down into smaller, 2C compounds. • Each 2C compound reacts with coenzyme A to form acetyl coenzyme A. Name the covalent bond in lipids that is hydrolysed by lipase. State the role of acetyl coenzyme A in respiration. Explain why lipids have a higher energy value than carbohydrates. The respiratory quotient, RQ, is used to show which substrate is being metabolised by cells. It can be determined using the equation below. RQ = molecules of carbon dioxide released molecules of oxygen taken in Lauric acid is a saturated fatty acid found in coconuts and has a chain of 12 carbon atoms. Complete the equation below which outlines the aerobic respiration of lauric acid. C12H24O2 + …….O2 12CO2 + 12H2O Calculate the RQ value for lauric acid. Show your working. Give your answer to 2 decimal places. answer =
9700_w17_qp_42
THEORY
2017
Paper 4, Variant 2
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Structures and compounds involved in respiration in anaerobic conditions include: A – pyruvate F – NAD B – reduced NAD G – ethanal C – ethanol H – lactate D – carbon dioxide I – oxygen E – cytoplasm J – mitochondrion Complete Table 7.1 by matching each description with one letter chosen from A to J to show the correct structure or compound. You may use each letter once, more than once or not at all. Table 7.1 description letter end product of glycolysis cellular location of respiration in anaerobic conditions end product of respiration in anaerobic conditions in yeast cells compound used to reduce pyruvate end product of respiration in anaerobic conditions in muscle cells gas released during alcoholic fermentation Respiration in anaerobic conditions in muscle cells during vigorous exercise can create an oxygen debt. Extra oxygen is breathed in after exercise to pay back the oxygen debt. Explain two ways in which the mammalian body uses this extra oxygen.
9700_w20_qp_41
THEORY
2020
Paper 4, Variant 1
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Structures and compounds involved in respiration in anaerobic conditions include: A – pyruvate F – NAD B – reduced NAD G – ethanal C – ethanol H – lactate D – carbon dioxide I – oxygen E – cytoplasm J – mitochondrion Complete Table 7.1 by matching each description with one letter chosen from A to J to show the correct structure or compound. You may use each letter once, more than once or not at all. Table 7.1 description letter end product of glycolysis cellular location of respiration in anaerobic conditions end product of respiration in anaerobic conditions in yeast cells compound used to reduce pyruvate end product of respiration in anaerobic conditions in muscle cells gas released during alcoholic fermentation Respiration in anaerobic conditions in muscle cells during vigorous exercise can create an oxygen debt. Extra oxygen is breathed in after exercise to pay back the oxygen debt. Explain two ways in which the mammalian body uses this extra oxygen.
9700_w20_qp_43
THEORY
2020
Paper 4, Variant 3
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outlines the first three stages of respiration in aerobic conditions. ATP × 2 ATP × 2 triose phosphate × 2 acetyl coenzyme A × 2 pyruvate × 2 ATP × 4 reduced NAD × 2 reduced NAD × 2 reduced NAD × 6 reduced FAD × 2 Krebs cycle × 2 molecule Y × 2 molecule Y × 4 glucose Name molecule Y in . Explain how shows that glycolysis involves oxidation. At one time it was thought that the oxidative phosphorylation of: • one molecule of reduced NAD results in the synthesis of 3 ATP molecules • one molecule of reduced FAD results in the synthesis of 2 ATP molecules. Using , a theoretical value for the net number of ATP molecules that are synthesised for each molecule of glucose can be calculated. Modern research has shown that the actual net number of ATP molecules synthesised for each glucose molecule respired is much lower than this theoretical value. Using , calculate the theoretical value for the net number of ATP molecules that are synthesised for each molecule of glucose respired in all phosphorylation reactions. Show your working. answer = Suggest two reasons why the actual net number of ATP molecules synthesised is less than the theoretical number. Outline the roles of NAD and FAD in aerobic respiration. Rotenone is used as an insecticide. Rotenone kills insects by inhibiting the transfer of electrons in the electron transport chain of the mitochondrion. Explain how rotenone affects ATP synthesis in the mitochondrion.
9700_w21_qp_41
THEORY
2021
Paper 4, Variant 1
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outlines the first three stages of respiration in aerobic conditions. ATP × 2 ATP × 2 triose phosphate × 2 acetyl coenzyme A × 2 pyruvate × 2 ATP × 4 reduced NAD × 2 reduced NAD × 2 reduced NAD × 6 reduced FAD × 2 Krebs cycle × 2 molecule Y × 2 molecule Y × 4 glucose Name molecule Y in . Explain how shows that glycolysis involves oxidation. At one time it was thought that the oxidative phosphorylation of: • one molecule of reduced NAD results in the synthesis of 3 ATP molecules • one molecule of reduced FAD results in the synthesis of 2 ATP molecules. Using , a theoretical value for the net number of ATP molecules that are synthesised for each molecule of glucose can be calculated. Modern research has shown that the actual net number of ATP molecules synthesised for each glucose molecule respired is much lower than this theoretical value. Using , calculate the theoretical value for the net number of ATP molecules that are synthesised for each molecule of glucose respired in all phosphorylation reactions. Show your working. answer = Suggest two reasons why the actual net number of ATP molecules synthesised is less than the theoretical number. Outline the roles of NAD and FAD in aerobic respiration. Rotenone is used as an insecticide. Rotenone kills insects by inhibiting the transfer of electrons in the electron transport chain of the mitochondrion. Explain how rotenone affects ATP synthesis in the mitochondrion.
9700_w21_qp_43
THEORY
2021
Paper 4, Variant 3
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is a diagram of a section through a mitochondrion. circular DNA P Q R S Using , state the letter which indicates the site of: • the Krebs cycle • oxidative phosphorylation • decarboxylation. Suggest one function for the circular DNA in . During respiration, exchange of substances takes place between the cytoplasm and the mitochondria. Complete the table below to list three substances that enter the mitochondria and three substances that leave the mitochondria. substance that enters the mitochondria substance that leaves the mitochondria The poison cyanide binds with cytochrome oxidase, one of the carriers in the electron transport system. Suggest how ingestion of cyanide by humans leads to death by muscle failure. Tripalmitin is a triglyceride. The chemical equation for the aerobic respiration of tripalmitin is: 2C51H98O6 + 145O2 102CO2 + 98H2O Calculate the RQ value for tripalmitin. Give your answer to 2 decimal places. Show your working. answer Explain why the usual RQ value for respiration in humans is between 0.7 and 1.0.
9700_m16_qp_42
THEORY
2016
Paper 4, Variant 2
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shows a transmission electron micrograph of a mitochondrion. B On , use the letter A with a label line to show a location where the Krebs cycle occurs. Name the structure labelled B on that forms part of the inner mitochondrial membrane. The inner mitochondrial membrane is the site of oxidative phosphorylation. Explain how the structure of the inner mitochondrial membrane is linked to its function. The activity of succinate dehydrogenase, an enzyme in the Krebs cycle, is used as a measure of the rate of respiration in the mitochondria. The redox reaction catalysed by succinate dehydrogenase is shown in . succinate succinate dehydrogenase fumarate e– The activity of succinate dehydrogenase can be measured using a redox indicator. Name a redox indicator and explain why this indicator can be used to measure the activity of succinate dehydrogenase. shows a ground squirrel, Ictidomys tridecemlineatus. In the winter, the ground squirrel curls into a spherical shape underground and sleeps for long periods. During this time, the ground squirrel switches between two states: • torpor, when the body temperature is maintained at 10 °C • euthermia, when the body temperature is maintained at 37 °C. Scientists used the activity of succinate dehydrogenase to investigate the rate of respiration in the mitochondria of ground squirrels. Mitochondria were extracted from liver and muscle samples of ground squirrels. The rate of respiration was measured at different concentrations of succinate and at temperatures that corresponded to torpor (10 °C) and euthermia (37 °C). The results are shown in . concentration of succinate / mmol dm–3 muscle at 37 °C liver at 37 °C muscle at 10 °C liver at 10 °C key rate of respiration / arbitrary units Describe the trends shown in . Explain the difference in the rates of respiration between liver at 37 °C and muscle at 37 °C. During torpor in ground squirrels, muscle tissue uses more energy than liver tissue. Suggest one reason for this difference.
9700_m21_qp_42
THEORY
2021
Paper 4, Variant 2
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