12.2. Respiration
A subsection of Biology, 9700, through 12. Energy and respiration
Listing 10 of 158 questions
is an outline diagram of the Krebs cycle. A two carbon acetyl group enters the cycle by combining with a molecule of oxaloacetate. A molecule of citrate is formed which is decarboxylated and dehydrogenated to regenerate the oxaloacetate. The letters P to V are steps in the cycle. fatty acids acetyl (2C) CoA CoA citrate (6C) intermediate (5C) intermediate (4C) intermediate (4C) intermediate (4C) intermediate (4C) oxaloacetate (4C) P Q R S T V NAD reduced NAD β – oxidation Explain what is meant by the following terms: decarboxylation dehydrogenation Using the letters in the cycle, state where decarboxylation is taking place. shows that fatty acids can be converted into acetyl coenzyme A (acetyl CoA) by a process known as oxidation. Both this process and the Krebs cycle require NAD. The hydrogen atoms released reduce the NAD molecules. State the number of reduced NAD molecules that are formed in the Krebs cycle from one acetyl group that enters the cycle from acetyl CoA. State where the reduced NAD molecules are re-oxidised and describe what happens to the hydrogen atoms. Describe the role of reduced NAD in respiring yeast cells in the absence of oxygen. Describe how the production of lactate in muscle tissue differs from anaerobic respiration in yeast.
9700_s10_qp_42
THEORY
2010
Paper 4, Variant 2
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is an outline diagram of the Krebs cycle. A two carbon acetyl group enters the cycle by combining with a molecule of oxaloacetate. A molecule of citrate is formed which is decarboxylated and dehydrogenated to regenerate the oxaloacetate. The letters P to V are steps in the cycle. fatty acids acetyl (2C) CoA CoA citrate (6C) intermediate (5C) intermediate (4C) intermediate (4C) intermediate (4C) intermediate (4C) oxaloacetate (4C) P Q R S T V NAD reduced NAD β – oxidation Explain what is meant by the following terms: decarboxylation dehydrogenation Using the letters in the cycle, state where decarboxylation is taking place. shows that fatty acids can be converted into acetyl coenzyme A (acetyl CoA) by a process known as oxidation. Both this process and the Krebs cycle require NAD. The hydrogen atoms released reduce the NAD molecules. State the number of reduced NAD molecules that are formed in the Krebs cycle from one acetyl group that enters the cycle from acetyl CoA. State where the reduced NAD molecules are re-oxidised and describe what happens to the hydrogen atoms. Describe the role of reduced NAD in respiring yeast cells in the absence of oxygen. Describe how the production of lactate in muscle tissue differs from anaerobic respiration in yeast.
9700_s10_qp_43
THEORY
2010
Paper 4, Variant 3
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Complete the following passage about ATP by writing in the missing words. All living organisms use energy. The most common immediate source of energy is adenosine triphosphate (ATP) which is used in every cell for the movement of ions against a concentration gradient, known as . ATP is known as the universal currency of energy. ATP is a phosphorylated nucleotide which is known as a ‘high energy’ molecule. It is made of an organic base, adenine, a 5 carbon sugar named and three phosphate groups. ATP is very soluble in and easily transported within the cell. The removal of the outer phosphate group by the process of releases energy. The energy released as a result of this reaction can be channelled directly into other reactions in the cell. A certain proportion of this energy is lost as . ATP is continually broken down and is reformed at a fast rate by the process of respiration. During a sporting event an athlete may have to carry out anaerobic respiration in addition to aerobic respiration to produce sufficient ATP. outlines both processes in a muscle cell and shows how a liver cell is linked to these processes. Liver cell Muscle cell glucose additional oxygen blood lactate blood glucose glucose lactate glycolysis ATP pyruvate link reaction acetyl coA Krebs cycle carbon dioxide oxidative phosphorylation ATP water You may refer to in answering questions to below. Glucose produced in the liver cell can be released into the blood to maintain blood glucose concentration. State one use of glucose within the liver cell. Suggest why anaerobic respiration is said to be less efficient than aerobic respiration. Complete the table to indicate, within the muscle cell, the precise locations of glycolysis, the link reaction, the Krebs cycle and oxidative phosphorylation. process precise location glycolysis link reaction Krebs cycle oxidative phosphorylation Glucose is phosphorylated at the start of glycolysis in the muscle cell. Suggest why this phosphorylated glucose does not diffuse out of the cell into the surrounding tissue fluid. Additional oxygen is required in the metabolic pathways involved in the conversion of lactate to glucose. State the term given to this additional oxygen.
9700_s11_qp_41
THEORY
2011
Paper 4, Variant 1
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Outline the process of glycolysis in a mammalian cell. Within a mammalian cell, ATP can be produced in a number of ways, including: • substrate level phosphorylation during the Krebs cycle • oxidative phosphorylation. Table 7.1 compares both processes. Complete Table 7.1. Use a tick () if the statement is correct or a cross () if the statement is incorrect. The first row has been done for you. Table 7.1 statement substrate level phosphorylation oxidative phosphorylation enzymes are involved   occurs in cytoplasm occurs in mitochondria channel proteins are involved An investigation into the RQ values of germinating maize seeds was carried out. • A sample of maize seeds was soaked in water for one hour. • The mean RQ value of some of the seeds was then calculated and the remaining seeds were then planted in soil. • After 12 hours, the mean RQ value of some of the planted seeds was calculated. • The remaining seeds were allowed to germinate and grow into seedlings. • After 21 days, the mean RQ value of some of the seedlings was calculated. Table 7.2 shows the results of the investigation. Table 7.2 stage of germination and growth mean RQ seeds soaked in water 5.6 seeds after 12 hours in the soil 0.8 seedlings after 21 days 1.0 Suggest an explanation for each of the RQ values shown in Table 7.2. seeds soaked in water seeds after 12 hours in the soil seedlings after 21 days
9700_s15_qp_41
THEORY
2015
Paper 4, Variant 1
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Outline the process of glycolysis in a mammalian cell. Within a mammalian cell, ATP can be produced in a number of ways, including: • substrate level phosphorylation during the Krebs cycle • oxidative phosphorylation. Table 7.1 compares both processes. Complete Table 7.1. Use a tick () if the statement is correct or a cross () if the statement is incorrect. The first row has been done for you. Table 7.1 statement substrate level phosphorylation oxidative phosphorylation enzymes are involved   occurs in cytoplasm occurs in mitochondria channel proteins are involved An investigation into the RQ values of germinating maize seeds was carried out. • A sample of maize seeds was soaked in water for one hour. • The mean RQ value of some of the seeds was then calculated and the remaining seeds were then planted in soil. • After 12 hours, the mean RQ value of some of the planted seeds was calculated. • The remaining seeds were allowed to germinate and grow into seedlings. • After 21 days, the mean RQ value of some of the seedlings was calculated. Table 7.2 shows the results of the investigation. Table 7.2 stage of germination and growth mean RQ seeds soaked in water 5.6 seeds after 12 hours in the soil 0.8 seedlings after 21 days 1.0 Suggest an explanation for each of the RQ values shown in Table 7.2. seeds soaked in water seeds after 12 hours in the soil seedlings after 21 days
9700_s15_qp_43
THEORY
2015
Paper 4, Variant 3
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ATP and coenzyme A both play important roles in respiration. represents the molecular structure of coenzyme A. mercapto - ethylamine P pantothenate P P With reference to , state two structural similarities between coenzyme A and ATP. Describe the role of coenzyme A in respiration. summarises the reactions that take place after glucose has entered a certain type of cell. glycogen phosphorylated glucose glucose other metabolic pathway cell reaction ) reaction * Suggest one type of cell in which the reactions shown in could occur. State the mechanism by which glucose enters the cell. Name the type of reaction occurring at F and the type of reaction occurring at G. F G With reference to , suggest one example of an ‘other metabolic pathway’ for phosphorylated glucose.
9700_s16_qp_42
THEORY
2016
Paper 4, Variant 2
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Questions Discovered
158