12. Energy and respiration
A section of Biology, 9700
Listing 10 of 192 questions
ATP is synthesised from ADP and Pi in a phosphorylation reaction. State the two different ways in which this phosphorylation reaction occurs in aerobic respiration. Coenzymes are important in all four stages of aerobic respiration. Describe and explain the role of the coenzymes NAD and FAD in aerobic respiration. The enzyme pyruvate dehydrogenase catalyses the link reaction. Pyruvate dehydrogenase is inhibited when the ratio of acetyl coenzyme A to coenzyme A increases. Suggest the importance of this inhibition to the functioning of the cell.
9700_s22_qp_43
THEORY
2022
Paper 4, Variant 3
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Glycolysis is a biochemical pathway that occurs in the cytoplasm of cells. In glycolysis, a molecule of glucose is metabolised to two molecules of pyruvate. The process is outlined in . pyruvate triose phosphate glucose fructose 1, 6-bisphosphate 2ATP 2ADP 2ATP 2ADP reduced NAD NAD pyruvate triose phosphate 2ATP 2ADP reduced NAD NAD Explain why glucose is phosphorylated at the beginning of glycolysis. Suggest one use of the reduced NAD that is produced in glycolysis. Name the type of phosphorylation reaction by which ATP is made during glycolysis. Pyruvate can enter the mitochondrion by active transport. Describe the main conditions that are required for pyruvate to enter the mitochondrion by active transport. Pyruvate is involved in the link reaction in the matrix of the mitochondrion. Describe the link reaction.
9700_s23_qp_42
THEORY
2023
Paper 4, Variant 2
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outlines some of the steps of glycolysis. glucose step 1 step 2 glucose 6–phosphate fructose 6–phosphate fructose 1, 6–bisphosphate triose phosphate triose phosphate pyruvate pyruvate step 3 step 4 step 5 State the precise location of glycolysis in the cell. With reference to : state the steps where phosphorylation occurs state the step where oxidation occurs name the type of reaction by which ATP is made during step 5. Some cancer cells have different metabolic requirements from normal cells. These cancer cells obtain most of their ATP from glycolysis, even if oxygen is available. State how the glucose and oxygen requirements of these cancer cells differ from normal cells.
9700_w18_qp_41
THEORY
2018
Paper 4, Variant 1
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outlines some of the steps of glycolysis. glucose step 1 step 2 glucose 6–phosphate fructose 6–phosphate fructose 1, 6–bisphosphate triose phosphate triose phosphate pyruvate pyruvate step 3 step 4 step 5 State the precise location of glycolysis in the cell. With reference to : state the steps where phosphorylation occurs state the step where oxidation occurs name the type of reaction by which ATP is made during step 5. Some cancer cells have different metabolic requirements from normal cells. These cancer cells obtain most of their ATP from glycolysis, even if oxygen is available. State how the glucose and oxygen requirements of these cancer cells differ from normal cells.
9700_w18_qp_43
THEORY
2018
Paper 4, Variant 3
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The results of investigations carried out on mitochondria show how the structure of a mitochondrion is related to its role in aerobic respiration. • Intact mitochondria (not damaged) were removed from cells. • A technique was used to remove the outer mitochondrial membrane, leaving the inner membrane intact. • The inner mitochondrial membrane was separated from the contents of the matrix so that both could be analysed. The removal of the outer membranes of mitochondria involves placing the organelles in pure water. This results in the rupture of the outer membrane. The inner mitochondrial membrane does not rupture and remains intact. Suggest and explain why the inner membrane of a mitochondrion remains intact when the organelle is placed in pure water. Name three molecules, other than coenzymes, that are found in the mitochondrial matrix and explain their role in aerobic respiration. The inner membrane contains a very high proportion of the molecule cardiolipin. Cardiolipin makes the membrane impermeable to some ions. Suggest why the inner membrane contains a very high proportion of cardiolipin. In further experiments it was found that, in an intact mitochondrion: • there is a membrane potential across the inner mitochondrial membrane, with the matrix having a negative charge • the transport of ATP, ADP and inorganic phosphate (Pis driven by the membrane potential across the inner membrane. shows the location of some inner membrane carrier proteins. + + + + + + + + + + + + + + + + + + + + + + + + – – – – – – – – – – – – – – – – – – – – – – ADP ADP ATP H+ intermembrane space carrier protein matrix outer membrane (freely permeable to ATP, ADP + Pinner membrane Pi Pi H+ ATP Reduced NAD and reduced FAD transfer hydrogen atoms to carriers located in the inner mitochondrial membrane. Explain how hydrogen atoms from reduced NAD and reduced FAD lead to a membrane potential forming across the inner mitochondrial membrane during oxidative phosphorylation. Suggest and explain how Pi is transported across the inner membrane of the mitochondrion into the matrix. Suggest the advantages of linking ATP transport to ADP transport across the inner membrane of the mitochondrion.
9700_w22_qp_41
THEORY
2022
Paper 4, Variant 1
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The results of investigations carried out on mitochondria show how the structure of a mitochondrion is related to its role in aerobic respiration. • Intact mitochondria (not damaged) were removed from cells. • A technique was used to remove the outer mitochondrial membrane, leaving the inner membrane intact. • The inner mitochondrial membrane was separated from the contents of the matrix so that both could be analysed. The removal of the outer membranes of mitochondria involves placing the organelles in pure water. This results in the rupture of the outer membrane. The inner mitochondrial membrane does not rupture and remains intact. Suggest and explain why the inner membrane of a mitochondrion remains intact when the organelle is placed in pure water. Name three molecules, other than coenzymes, that are found in the mitochondrial matrix and explain their role in aerobic respiration. The inner membrane contains a very high proportion of the molecule cardiolipin. Cardiolipin makes the membrane impermeable to some ions. Suggest why the inner membrane contains a very high proportion of cardiolipin. In further experiments it was found that, in an intact mitochondrion: • there is a membrane potential across the inner mitochondrial membrane, with the matrix having a negative charge • the transport of ATP, ADP and inorganic phosphate (Pis driven by the membrane potential across the inner membrane. shows the location of some inner membrane carrier proteins. + + + + + + + + + + + + + + + + + + + + + + + + – – – – – – – – – – – – – – – – – – – – – – ADP ADP ATP H+ intermembrane space carrier protein matrix outer membrane (freely permeable to ATP, ADP + Pinner membrane Pi Pi H+ ATP Reduced NAD and reduced FAD transfer hydrogen atoms to carriers located in the inner mitochondrial membrane. Explain how hydrogen atoms from reduced NAD and reduced FAD lead to a membrane potential forming across the inner mitochondrial membrane during oxidative phosphorylation. Suggest and explain how Pi is transported across the inner membrane of the mitochondrion into the matrix. Suggest the advantages of linking ATP transport to ADP transport across the inner membrane of the mitochondrion.
9700_w22_qp_43
THEORY
2022
Paper 4, Variant 3
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Isolated mitochondria were used to investigate respiration. • Mitochondria were extracted from respiring mammalian cells and incubated in a buffer solution. • Pyruvate and inorganic phosphate (Pwere added at time zero. • ADP was added one minute later. • The oxygen concentration of the buffer solution containing mitochondria was monitored throughout the investigation. The results of the investigation are shown in . time / min phase A phase B phase C pyruvate and Pi added ADP added oxygen concentration of buffer solution containing mitochondria Suggest why the line of the graph in is steeper during phase B than during phase A. Suggest why the line of the graph starts to level out in phase C. Some plants, such as rice, grow with their roots submerged in water. shows a group of rice plants. Explain how rice is adapted to grow with its roots submerged in water.
9700_m19_qp_42
THEORY
2019
Paper 4, Variant 2
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Questions Discovered
192