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5.4 TCA Cycle β Test 1
Q1. Which two enzymes are glyoxylate-cycle-specific?β Isocitrate lyase and malate synthase
Q2. Which two enzymes are glyoxylate-cycle-specific? (variant)β Isocitrate lyase and malate synthase
Q3. The enzyme responsible for the conversion of citrate to isocitrate in the TCA cycle is:β Aconitase
Q4. The function of mitochondrial aconitase in the TCA cycle is:β Isomerisation
Q5. In the Krebs cycle, Ξ±-ketoglutarate dehydrogenase catalyses which reaction?β Oxidation and decarboxylation
Q6. The tricarboxylic acid cycle has:β Both catabolic and anabolic functions
Q7. In the Krebs cycle, two moles of glucose produce how many moles of ATP/GTP by substrate-level phosphorylation within the cycle?β 4 moles
Q8. The pyruvate dehydrogenase reaction involves all the following cofactors EXCEPT:β Biotin
Q9. In the Krebs cycle, citrate loses two of its six carbons as COβ. Which two carbons are lost?β C1 and C6
Q10. In the Krebs cycle, citrate loses two of its six carbons as COβ during conversion to oxaloacetate. Which two carbons are lost? (variant)β C1 and C6
Q11. A redox reaction in the citric acid cycle that does NOT use NADβΊ to accept electrons is the oxidation of:β Succinate
Q12. Which enzyme cannot carry out a reversible reaction in the citric acid cycle?β Citrate synthase
Q13. Which enzyme of the Krebs cycle is found in the inner mitochondrial membrane?β Succinate dehydrogenase
Q14. The last step in the Krebs cycle is the breakdown/conversion of:β Malate
Q15. The matrix of mitochondria contains:β Citric acid cycle intermediates
Q16. Which one of the following biochemical reactions is an oxidative decarboxylation?β Pyruvate to acetyl-CoA
Q17. Which enzyme system does NOT perform oxidative decarboxylation?β Succinate dehydrogenase
Q18. Biological oxidation in the Krebs cycle ultimately involves which molecule as the final electron acceptor (via the ETC)?β Oβ
Q19. Which one of the following is a stoichiometric (not catalytic) cofactor of the pyruvate dehydrogenase complex?β Coenzyme A
Q20. Pyruvate dehydrogenase is a multi-enzyme complex. Which is NOT a cofactor for PDH?β Glutathione (GSH)
5.4 TCA Cycle β Test 2
Q21. Pyruvate dehydrogenase is a multi-enzyme complex requiring many cofactors. Which is NOT a cofactor for PDH? (variant)β Glutathione (GSH)
Q22. The formation of acetyl-CoA from pyruvic acid is the result of:β Oxidative decarboxylation
Q23. Which enzyme is crucial for a cell to ensure balanced supplies of oxaloacetate and acetyl-CoA for citrate biosynthesis?β Pyruvate carboxylase
Q24. Which enzymatic reaction in the citric acid cycle produces a high-energy phosphate compound?β Succinyl-CoA synthetase
Q25. Only one step in the citric acid cycle yields a high phosphoryl-transfer-potential compound by substrate-level phosphorylation. It is catalyzed by:β Succinyl-CoA synthetase
Q26. In which step of the Krebs cycle does FAD participate as an electron acceptor?β Succinate to fumarate
Q27. In glycolysis and the citric acid cycle, the only dehydrogenase to use FAD as a cofactor is:β Succinate dehydrogenase
Q28. Succinate dehydrogenase is located in which compartment of the animal cell?β Mitochondria
Q29. In the Krebs cycle, GTP/ATP is released between:β Succinyl-CoA β succinate
Q30. Which one of the following is NOT true of the Krebs cycle (per glucose)?β Three molecules of NADH are produced per molecule of glucose
Q31. The main function of the Krebs cycle is to:β Generate electron carriers (NADH, FADHβ) for the electron transport chain
Q32. Put the compounds in correct order during the citric acid cycle: I. Oxaloacetate II. Fumarate III. Malate IV. Succinateβ IV, II, III, I
Q33. Which of the following is NOT a product of the Krebs cycle?β cAMP
Q34. The energy-rich fuel molecules produced in one turn of the TCA cycle are:β 1 GTP, 3 NADH and 1 FADHβ
Q35. When 3 molecules of acetyl-CoA are fed into the TCA cycle, the products are:β 3 GTP, 6 COβ, 9 NADH, 3 FADHβ
Q36. Identify the correct sequence(s) of reactions in the citric acid cycle: (i) pyruvate β citrate β oxaloacetate (ii) citrate β Ξ±-ketoglutarate β isocitrate (iii) citrate β aconitate β isocitrate (iv) succinate β fumarate β malateβ iii & iv
Q37. Identify the correct sequence(s) of reactions in the citric acid cycle (variant): (i) pyruvate β citrate β oxaloacetate (ii) citrate β Ξ±-ketoglutarate β isocitrate (iii) citrate β aconitate β isocitrate (iv) succinate β fumarate β malateβ iii & iv
Q38. Which of the following are key regulatory enzymes of the citric acid cycle?β Isocitrate dehydrogenase and Ξ±-ketoglutarate dehydrogenase
Q39. The conversion of succinate to fumarate in the TCA cycle can be described as:β Oxidation (dehydrogenation)