Unit 6: Metabolism - Practice Quiz

1 What is the main energy currency of the cell?

2 What type of reaction releases free energy?

3 Which molecule commonly carries high-energy electrons in metabolism?

4 Where does glycolysis occur in a eukaryotic cell?

5 What is the starting molecule of glycolysis?

6 What is the final product of glycolysis under aerobic conditions?

7 Which enzyme catalyzes the major rate-limiting step of glycolysis?

8 Where does the TCA cycle occur in eukaryotic cells?

9 Which molecule enters the TCA cycle by combining with oxaloacetate?

10 How many carbon dioxide molecules are released from one acetyl-CoA during one turn of the TCA cycle?

11 Which molecule is regenerated at the end of the TCA cycle?

12 Where does the pentose phosphate pathway occur?

13 What reducing equivalent is mainly produced by the pentose phosphate pathway?

14 Which five-carbon sugar is produced by the pentose phosphate pathway?

15 Where is the electron transport chain located in mitochondria?

16 What is the final electron acceptor in the electron transport chain?

17 Which enzyme synthesizes ATP during oxidative phosphorylation?

18 Where does most ß-oxidation of fatty acids occur?

19 What two-carbon product is formed during each cycle of ß-oxidation?

20 Where does fatty acid synthesis mainly occur in a eukaryotic cell?

21 A reaction has a positive standard free-energy change but proceeds forward inside a cell. Which explanation is most appropriate?

22 If the concentrations of products increase while reactant concentrations remain constant, what generally happens to the free-energy change of a forward reaction?

23 A cell has a high ATP concentration and a low AMP concentration. Which glycolytic enzyme is most likely inhibited under these conditions?

24 What is the net yield from the anaerobic conversion of one glucose molecule to two lactate molecules?

25 A mutation greatly reduces the activity of pyruvate kinase in a cell. Which immediate metabolic change is most likely?

26 Which TCA-cycle enzyme is directly inhibited by high NADH and activated by ADP, reflecting the cell's energy state?

27 How many NADH molecules are produced in the TCA cycle per acetyl-CoA molecule oxidized?

28 If oxaloacetate becomes severely depleted, what is the most likely effect on acetyl-CoA oxidation?

29 A rapidly dividing cell requires ribose-5-phosphate for nucleotide synthesis but has little need for NADPH. Which pathway strategy is most suitable?

30 Why are red blood cells especially dependent on the pentose phosphate pathway?

31 A deficiency of glucose-6-phosphate dehydrogenase makes erythrocytes more vulnerable to oxidative stress because it reduces production of which molecule?

32 If complex IV is blocked, which immediate effect is expected in the mitochondrial electron transport chain?

33 An uncoupling agent allows protons to cross the inner mitochondrial membrane without passing through ATP synthase. What is the likely result?

34 Why does NADH generally yield more ATP than FADH during oxidative phosphorylation?

35 How many cycles of -oxidation are required to completely degrade a saturated fatty acid containing 16 carbon atoms?

36 A defect in carnitine acyltransferase I would most directly impair which process?

37 Complete oxidation of one palmitoyl-CoA molecule produces how many acetyl-CoA molecules?

38 What is the principal role of malonyl-CoA during fatty acid synthesis?

39 Why does malonyl-CoA inhibit carnitine acyltransferase I during fatty acid synthesis?

40 Which reducing molecule is consumed during the reduction steps of fatty acid synthesis?

41 A reaction has , but its actual concentrations give at . What is the most accurate conclusion?

42 A coupled reaction has and is driven by ATP hydrolysis with . Which statement is correct?

43 A hepatocyte has high ATP and citrate concentrations but low fructose 2,6-bisphosphate. Which glycolytic response is most likely?

44 If glyceraldehyde 3-phosphate dehydrogenase is inhibited while oxygen is abundant, which immediate glycolytic consequence is expected?

45 A muscle cell expresses a pyruvate kinase variant with reduced affinity for phosphoenolpyruvate but normal allosteric regulation. Which change is most likely?

46 A mutation eliminates succinate dehydrogenase activity but leaves the other TCA enzymes intact. Which combination best describes the direct metabolic effects?

47 During intense exercise, a high NADH/NAD ratio inhibits several TCA reactions. Which additional effect most directly limits continued cycle operation?

48 A cell receives uniformly C-labeled acetyl-CoA during one TCA cycle turn. Why is no net labeled oxaloacetate expected after that first turn?

49 A rapidly dividing cell requires ribose 5-phosphate far more than NADPH. Which pathway arrangement best meets this demand?

50 An erythrocyte with severe glucose 6-phosphate dehydrogenase deficiency is exposed to an oxidant. Which event is most likely?

51 If transketolase activity is selectively inhibited, which biochemical requirement becomes especially important for the remaining pathway reactions?

52 A mitochondrial preparation consumes oxygen rapidly, but oxygen consumption is unaffected by oligomycin and ATP synthesis is absent. Which explanation best fits?

53 Rotenone inhibits complex I, but succinate still supports oxygen consumption in isolated mitochondria. Which conclusion is correct?

54 A mitochondrion has an intact electron transport chain but lacks a functional adenine nucleotide translocase. Which immediate effect is expected?

55 Complete mitochondrial oxidation of an even-chain saturated fatty acid containing 16 carbons yields how many acetyl-CoA, NADH, and FADH molecules?

56 A long-chain fatty acid cannot enter the mitochondrial matrix because carnitine palmitoyltransferase I is inhibited. Which process is most directly affected?

57 Oxidation of an odd-chain fatty acid produces propionyl-CoA as its final three-carbon fragment. Which pathway converts this product into a TCA intermediate?

58 A hepatocyte has abundant mitochondrial acetyl-CoA and NADPH but low cytosolic citrate. Which intervention most directly limits fatty acid synthesis?

59 Which change would most strongly increase fatty acid synthesis while simultaneously suppressing mitochondrial fatty acid oxidation?

60 For synthesis of one palmitate molecule from eight acetyl-CoA molecules, what are the required ATP and NADPH investments?