Biochemistry Test Bank – Topic 13In every slide, you will find a question with 2 – 5 choices.

The answers of the questions will be in the last slide, so don’t forget to write your answers (To check them 💪).

1. Citrate is converted to isocitrate by aconitase which contains:

A. Ca++.

B. Fe++.

C. Zn++.

D. Mg++.

2. The reaction succinyl COA to succinate requires:

A. CDP.

B. ADP.

C. GDP.

D. NADP+.

3. The carrier of the citric acid cycle is:

A. Succinate.

B. Fumarate.

C. Malate.

D. Oxaloacetate.

4. Pyruvate dehydrogenase complex and α-ketoglutarate dehydrogenase complex require the following for their oxidative decarboxylation:

A. CoA-SH and Lipoic acid.

B. NAD+ and FAD.

C. CoA-SH and TPP.

D. CoA-SH, TPP,NAD+,FAD, Lipoate.

5. Oxidative decarboxylation of pyruvate requires:

A. NADP+.

B. Cytichromes.

C. Pyridoxal phosphate.

D. CoA-SH.

6. Tricarboxylic acid cycle to be continuous requires the regeneration of:

A. Pyruvic acid.

B. Oxaloacetic acid.

C. Oxoglutaric acid.

D. Malic acid.

7. Dehydrogenation of succinic acid to fumaric acid requires the following hydrogen carrier:

A. NAD+.

B. NADP+.

C. Flavoprotein.

D. Glutathione.

8. The number of molecules of ATP produced by the total oxidation of acetyl CoA in TCA cycle is:

A. 6.

B. 8.

C. 10.

D. 12.

9. Substrate level phosphorylation in TCA cycle is in step:

A. Isocitrate dehydrogenase.

B. Malate dehydrogenase.

C. Aconitase.

D. Succinate thiokinase.

10. One molecule of glucose gives ______ molecules of CO2 in TCA cycle.

A. 1.

B. 2.

C. 3.

D. 4.

11. Before pyruvic acid enters the TCA cycle it must be converted to:

A. Acetyl CoA.

B. Lactate.

C. α-ketoglutarate.

D. Citrate.

12. The formation of citrate from oxaloacetate and acetyl CoA is:

A. Oxidation.

B. Reduction.

C. Condensation.

D. Hydrolysis.

13. We can get ____ ATP in the succinate dehydrogenase step.

A. 1.

B. 2.

C. 3.

D. 4.

14. Out of 24 mols of ATP formed in TCA cycle, 2 molecules of ATP can be formed at “substrate level” by which of the following reaction ?

A. Citric acid → Isocitric acid.

B. Isocitrate → Oxaloacetate.

C. Succinic acid → Fumarate.

D. Succinylcat→ Succinic acid.

15. Which of the following statements regarding T.C.A cycle is true?

A. It is an anaerobic process.

B. It occurs in cytosol.

C. It contains no intermediates for Gluconeogenesis.

D. None of the above.

16. An allosteric enzyme responsible for controlling the rate of T.C.A cycle is:

A. Malate dehydrogenase.

B. Isocitrate dehydrogenase.

C. Fumarase.

D. Aconitase.

17. Electron transport and phosphorylation can be uncoupled by compounds that increase the permeability of the inner mitochondrial membrane to:

A. Electrons.

B. Protons.

C. Uncouplers.

D. All of the above.

18. An uncoupler of oxidative phosphorylation:

A. Inhibits electron transport and ATP synthesis.

B. Allow electron transport to proceed without ATP synthesis.

C. Inhibits electron transport without impairment of ATP synthesis.

D. Specially inhibits cytochrome b.

19. All of the following statements about the enzymic complex that carries out the synthesis of ATP during oxidative phosphorylation are correct except:

A. It is located on the matrix side of the inner mitochondrial membrane.

B. It is inhibited by oligomycin.

C. It can exhibit ATPase activity.

D. It can bind molecular O2.

20. The conversion of pyruvate to acetyl CoA and CO2:

A. Is reversible.

B. Involves the participation of lipoic acid.

C. Depends on the coenzyme biotin.

D. Occurs in the cytosol.

21. All enzymes of the TCA cycle reside in the mitochondrial membrane.

A. True.

B. False.

22. Which of the following is also known as Krebs cycle?

A. Electron transport chain.

B. Glycolysis.

C. TCA cycle.

D. DNA Replication.

23. How many reactions that occur in the TCA cycle transfer electrons from a substrate to an electron accepting enzyme?

A. 1.

B. 2.

C. 3.

D. 4.

24. Acetyl-CoA is a _____________ carbon compound.

A. 1.

B. 2.

C. 3.

D. 4.

25. In the TCA cycle, which of the following combines with Acetyl CoA to form a 6 carbon compound?

A. Oxaloacetate.

B. Glucose.

C. Pyruvate.

D. Thiamine.

26. The enzyme aconitase is responsible for ________________.

A. Polymerization.

B. Degradation.

C. Assembly.

D. Isomerization.

27. For each molecule of glucose, how many times does the TCA cycle proceed?

A. 1.

B. 2.

C. 3.

D. 4.

28. Which of the following is the prosthetic group of NADH dehydrogenase?

A. NADH.

B. FAD.

C. NADPH.

D. FMN.

29. If 2, 4-dinitrophenol (Uncoupler) is added to tightly coupled mitochondria that are actively oxidizing succinate ____________.

A. Electron flow will continue but ATP synthesis will not occur.

B. Electron flow will continue but ATP synthesis will be increased.

C. Electron flow will cease but ATP synthesis will continue.

D. Both electron flow and ATP synthesis will be ceased.

30. If the oxidative phosphorylation was uncoupled in the mitochondria then there is a/an ____________.

A. Decreased concentration of ADP in the mitochondria.

B. Decreased oxidative rate.

C. Increased inorganic phosphate in the mitochondria.

D. Decreased production of heat.

31. Which of the following takes place in substrate level phosphorylation?

A. Oxidation of one molecule of substrate is linked to synthesis of more than one ATP molecule.

B. High energy intermediate compounds cannot be isolated.

C. Only mitochondrial reactions participate in ATP formation.

D. Substrate reacts to form a product containing a high energy bond.

32. Chemiosmotic hypothesis does not involve ____________.

A. Only proton transport is strictly regulated, other positively charged ions can diffuse freely across the

mitochondrial membrane.

B. ATPase activity is reversible.

C. Proton flow into the mitochondria depends on the presence of ADP and Pi.

D. Electron transport by the respiratory chain pumps protons out of the mitochondria.

33. Which of the following accepts only one electron?

A. Cytochrome b.

B. Coenzyme Q.

C. FMN.

D. FAD.

34. ATP synthesis by chemiosmosis is by ____________.

A. ATP dehydrogenase.

B. Gyrase.

C. ATP synthase.

D. Dehydrogenase.

35. The measure of potential energy stored as a combination of proton and voltage gradients across membrane is termed as ____________.

A. Proton motive force.

B. Electron motive force.

C. Molecule motive force.

D. Ion motive force.

36. The acetyl-CoA formed in the cytosol is transported to ____________.

A. Mitochondrial matrix.

B. Microsomes.

C. ER.

D. Remains in cytosol.

37. Membrane potential and the proton gradient ____________.

A. Cancel one another when uncouplers are present.

B. Reinforce one another when respiratory inhibitors are present.

C. Are sufficient, separately to make ATP from ADP + Pi.

D. Are required to make ATP.

38. The regulation of oxidative phosphorylation depends on ____________.

A. Magnitude of ion motive force.

B. Magnitude of electron motive force.

C. Magnitude of proton motive force.

D. None of the mentioned.

39. Where does oxidative phosphorylation take place?

A. Ribosomes.

B. Nucleus.

C. Mitochondria.

D. Cell membrane.

40. NADP+ in its reduced form is ____________.

A. NAD.

B. NADH.

C. NADPH.

D. DPH.

41. Products of glucose oxidation essential for oxidative phosphorylation are:

A. Pyruvate.

B. Acetyl co-A.

C. NADPH and ATP.

D. NADH and FADH2.

42. Which effects the increased levels of hydrogen ions in the inter-membrane space of the mitochondria?

A. Increase ATP production.

B. Decreased levels of oxidative phosphorylation.

C. Increased levels of water in inter-membrane space.

D. Decreased levels of chemiosmosis.

43. Protein that contains a nucleic acid derivative of riboflavin is called _________.

A. Nucleic acid.

B. Amino acid.

C. Flavoprotein.

D. None of the above.

44. A lipid-soluble benzoquinone with a long isoprenoid side chain is?

A. Ubiquinone.

B. Cytochrome b.

C. Cytochrome c.

D. Cytochrome a.

45. Complex 1 is also called _________.

A. NADH dehydrogenase.

B. Succinate dehydrogenase.

C. Cytochrome bc1 complex.

D. Cytochrome oxidase.

The key answers

Question No. Answers Question No. Answers Question No. Answers Question No. Answers Question No. Answers

1. B 10. D 19. D 28. D 37. D

2. C 11. A 20. B 29. A 38. C

3. D 12. C 21. B 30. C 39. C

4. D 13. B 22. C 31. D 40. C

5. D 14. D 23. D 32. A 41. D

6. B 15. D 24. B 33. A 42. A

7. C 16. B 25. A 34. C 43. C

8. D 17. B 26. D 35. A 44. A

9. D 18. B 27. B 36. A 45. A