1 markGlycolysis is the first stage of cellular respiration. This process occurs in the cytoplasm and can happen in both aerobic and anaerobic conditions. Which of the following statements about glycolysis is correct?
Pyruvate produced during glycolysis remains in the cytoplasm.
NADPH, pyruvate and ATP are products of glycolysis.
Electrons transferred during glycolysis enter the electron transport chain.
Glycolysis can occur in the absence of NAD+.
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1 markElectron transport chain inhibitors are molecules that disrupt the electron transport chain in cells. Some electron transport chain inhibitors function as uncouplers, breaking the connection between the electron transport chain and ATP synthase. Which of the following is the most likely effect of an uncoupler on oxidative phosphorylation?
Oxygen will still be used up but less ATP will be produced.
Oxygen use and ATP production will both decrease.
Fewer protons will be pumped across the inner mitochondrial membrane.
Less heat is generated.
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1 markThe Krebs cycle, also known as the citric acid cycle, is a series of reactions that occur in the mitochondrial matrix. It uses acetyl-CoA as a substrate and produces high-energy electron carriers, which are then used in the electron transport chain. Figure 1 shows a representation of the Krebs cycle.
Which of the following descriptions of the Krebs cycle shown in Figure 1 are correct?
Oxidation of coenzymes occurs at stages 3, 4, 6 and 8.
Phosphorylation occurs at stage 5.
Carbon dioxide is a Krebs cycle reactant.
NADH is the only reduced coenzyme produced by the Krebs cycle.
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1 markA researcher investigated respiration in yeast cells. They set up an airtight container with yeast and a suitable respiratory substrate. The oxygen, carbon dioxide and ethanol concentrations in the container were measured over 10 hours. The results of this experiment are shown in Figure 1 below.
Which of the following claims is best supported by the data in Figure 1?
Yeast cells begin alcohol fermentation when oxygen concentration drops below a certain level.
Yeast cells rely on alcohol fermentation to produce ATP.
Yeast cells switch from aerobic respiration to alcohol fermentation when oxygen concentration drops below a certain level.
Yeast cells can only respire aerobically.
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1 markThe electron transport chain consists of a series of protein complexes embedded in the inner mitochondrial membrane. Protein complexes I, II, III and IV are illustrated in Figure 1 below, along with some of the events that occur on complexes I and II.
Amobarbital is an example of an oxidative phosphorylation inhibitor. It binds to complex I in the electron transport chain. Which of the following describes a consequence of exposure to amobarbital?
An increased proton concentration inside the intermembrane space.
An increased ratio of NADH to NAD+.
Increased phosphorylation of ADP.
Increased oxygen consumption.
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