12.2. Respiration
A subsection of Biology, 9700, through 12. Energy and respiration
Listing 10 of 158 questions
Chemiosmosis is the term used to describe the synthesis of ATP using a proton gradient across a membrane in a mitochondrion or chloroplast. It was first demonstrated by Peter Mitchell in 1961. • In some of his experiments, Peter Mitchell used mitochondria that had been isolated from cells. • The mitochondria were kept in liquid, in glass dishes, to which ADP, Pi and other substances were added. • The temperature, pH and water potential were kept constant. • After a period of time he checked for the presence of ATP. The contents of some of the dishes are shown in the table below. Complete the table using a tick (3) if ATP was produced and a cross (7) if no ATP was produced. dish contents ATP produced mitochondria + ADP + Pi + acetyl CoA + oxygen mitochondria + ADP + Pi + acetyl CoA mitochondria + ADP + Pi + low concentration of protons (H+) mitochondria + ADP + Pi + high concentration of protons (H+) Explain the consequences to a mitochondrion if the water potential of the liquid in the dishes is higher than the water potential of the mitochondrial matrix. State the specific role of oxygen in the mitochondrion. Name the enzyme used to produce ATP in chemiosmosis. Describe the role of the inner mitochondrial membrane in chemiosmosis.
9700_w17_qp_41
THEORY
2017
Paper 4, Variant 1
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Chemiosmosis is the term used to describe the synthesis of ATP using a proton gradient across a membrane in a mitochondrion or chloroplast. It was first demonstrated by Peter Mitchell in 1961. • In some of his experiments, Peter Mitchell used mitochondria that had been isolated from cells. • The mitochondria were kept in liquid, in glass dishes, to which ADP, Pi and other substances were added. • The temperature, pH and water potential were kept constant. • After a period of time he checked for the presence of ATP. The contents of some of the dishes are shown in the table below. Complete the table using a tick (3) if ATP was produced and a cross (7) if no ATP was produced. dish contents ATP produced mitochondria + ADP + Pi + acetyl CoA + oxygen mitochondria + ADP + Pi + acetyl CoA mitochondria + ADP + Pi + low concentration of protons (H+) mitochondria + ADP + Pi + high concentration of protons (H+) Explain the consequences to a mitochondrion if the water potential of the liquid in the dishes is higher than the water potential of the mitochondrial matrix. State the specific role of oxygen in the mitochondrion. Name the enzyme used to produce ATP in chemiosmosis. Describe the role of the inner mitochondrial membrane in chemiosmosis.
9700_w17_qp_43
THEORY
2017
Paper 4, Variant 3
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ATP is needed for many metabolic processes in living organisms. Describe the properties of ATP that make it suitable for its role as the universal energy currency. Suggest why ATP is needed for protein synthesis. is a diagram of mitochondrion. C B A E D diameter 0.72 μm length 5.25 μm Complete Table 6.1 using the letters A to E from . Each letter may be used once, more than once, or not at all. Table 6.1 statement letter the site of the Krebs Cycle a phospholipid bilayer impermeable to H+ ions the site of translation Assume that the mitochondrion in is a cylinder. Calculate the surface area of this mitochondrion. Use the formula: Surface area of cylinder = 2πr 2 + 2πrh Show your working. surface area = µm2 The inner membrane of the mitochondrion has a much larger surface area than the outer membrane because of the presence of cristae. Different cell types vary in the number of cristae present per mitochondrion. Cardiac muscle cells have mitochondria with a very large number of cristae. Suggest and explain why cardiac muscle cells have mitochondria with very large numbers of cristae.
9700_w21_qp_42
THEORY
2021
Paper 4, Variant 2
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Some organisms carry out respiration in anaerobic conditions when oxygen is not available or when there is a low concentration of oxygen. In yeast and some plants, this is called ethanol fermentation. In mammals, it is called lactate fermentation. outlines ethanol fermentation and lactate fermentation. glucose pyruvate D B B A C C ethanol ethanol fermentation lactate fermentation lactate Identify substances A–D. A B C D Explain how processes such as ethanol fermentation and lactate fermentation allow cells to continue to function in the absence of oxygen. The cereal crop rice, Oryza sativa, grows in fields that are flooded with water. The roots of the rice plants are submerged in water that contains very little oxygen. Describe and explain how rice plants are adapted to grow in flooded fields.
9700_w23_qp_42
THEORY
2023
Paper 4, Variant 2
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