Bioenergetic MCQs

By: Prof. Dr. Fazal Rehman | Last updated: May 22, 2025

1. : Which redox couple reacts directly with oxygen?
(A) Cytochrome C
(B) FADH2
(C) Cytochrome a3
(D) Complex V

2. : How many electrons are used by cytochrome oxidase to reduce O₂ in the respiratory chain?
(A) One
(B) Four
(C) Three
(D) Two

3. : When is it proper to write the reaction: ΔG⁰ = -RT lnKeq?
(A) When ΔG = 0
(B) Always
(C) When Keq = 1
(D) When all reactants and products are at unimolar concentrations

4. : Transfer of electrons from NADH to molecular oxygen can generate how much energy (kcal/mol)?
(A) 1.14 kcal/mol
(B) 82.0 kcal/mol
(C) 21.9 kcal/mol
(D) 52.6 kcal/mol

5. : Which statement regarding mitochondria is true?
(A) Calcium ions can freely diffuse through the inner membrane
(B) The inner membrane is folded into cristae to decrease matrix volume
(C) The matrix is a protein-rich gel that contains the enzymes involved in oxidative phosphorylation
(D) Outer membrane is permeable to most molecules, whereas inner membrane is impermeable to most

6. : Which is true for living cells and organisms?
(A) Are closed systems
(B) Exchange energy and material with their surroundings
(C) Exchange energy but not matter with their surroundings
(D) Are at equilibrium with their surroundings

7. : Which vitamin is not a component of the electron transport chain?
(A) Nicotinamide
(B) Riboflavin
(C) Ubiquinone
(D) Biotin

8. : Which redox component has the most negative redox potential (E°)?
(A) NADH
(B) Cytochrome C
(C) FADH2
(D) Coenzyme Q

9. : Which gives the maximum (negative) free energy of hydrolysis?
(A) ATP → ADP + Pi
(B) Phosphocreatine
(C) Phosphoenolpyruvate
(D) 1,3-bisphosphoglycerate

10. : Which one of the following ETC components is not permanently attached to an enzyme or a protein?
(A) Cytochrome oxidase
(B) Cytochrome C
(C) Iron-Sulfur clusters
(D) Ubiquinone

11. : A chemical reaction is more likely to occur spontaneously if:
(A) The products are more complex than the reactants
(B) The products are more disordered than the reactants
(C) The system takes up heat from surroundings
(D) The system gains free energy

12. : Which carbon-containing molecule is most oxidized?
(A) Carbon dioxide
(B) Methane
(C) Carbon monoxide
(D) Ethanol

13. : The free energy change, ΔG:
(A) Is equal to zero at equilibrium
(B) Is directly proportional to the standard free energy change
(C) Can only be calculated when reactants and products are at 1 M concentration
(D) Is equal to -RT lnKeq

14. : What is the voltage difference between cytosolic and matrix sides of the inner mitochondrial membrane during electron transport?
(A) 1.424 V
(B) 0.14 V
(C) 2.3 V
(D) 2.4 V

15. : Under what condition of Keq will the reaction proceed in the forward direction?
(A) If Keq is less than 1
(B) If Keq is 0
(C) If Keq is negative
(D) If Keq is greater than 1

16. : Which is true regarding ATP and ADP in intact cells?
(A) Magnesium binds with ATP only
(B) Manganese binds with ATP only
(C) Manganese binds with ADP and ATP
(D) Magnesium binds with ADP and ATP

17. : Cyanide is a poison because it inhibits respiration by:
(A) Combination with Red Blood cells
(B) Inhibition of Succinate-Q reductase
(C) Inhibition of NADH-Q reductase
(D) Inhibition of cytochrome oxidase

18. : Electrons from pyruvic acid enter the mitochondrial electron transport chain at:
(A) Co-enzyme Q
(B) NADH-Q reductase
(C) QH2-cytochrome reductase
(D) Cytochrome oxidase

19. : Electrons can be transferred from one molecule (electron donor) to another molecule (electron acceptor) by all of the following ways, except:
(A) As a hydrogen atom
(B) As a hydride ion
(C) Directly as an electron
(D) As a proton

20. : Which metal ion is associated with superoxide dismutase?
(A) Zn++
(B) Mn++
(C) Cu
(D) All of these

21. : Which is true for flavin nucleotides?
(A) They act as prosthetic groups
(B) They always accept two electrons
(C) They are utilized by oxygenases
(D) They have no reduction potential unless bound to a protein

22. : Which complex contains FMN?
(A) Cytochrome C
(B) FADH2
(C) NADH-Q Reductase
(D) Complex II

23. : Which is not a function of the mitochondrial electron transport system?
(A) Unidirectional proton pumping out of mitochondrial matrix
(B) Production of metabolic water
(C) ATP synthesis from ADP and Pi
(D) Oxidation of reduced NADH and FADH2

24. : Cytochrome Oxidase is a conjugated protein. It carries which prosthetic group, in addition to the heme group?
(A) Mn
(B) Co
(C) Mg
(D) Cu

25. : Which enzyme can catalyze the conversion of AMP to ADP?
(A) Creatine kinase
(B) Polyphosphate kinase
(C) Adenylate kinase
(D) Nucleoside diphosphate kinase

26. : The flavoproteins of the electron transport chain are complexed with:
(A) Cytochrome a
(B) Iron sulfur proteins
(C) Cytochrome C
(D) Cytochrome Q

27. : Mitochondrial β-oxidation is the oxidation of which of the following?
(A) Cholesterol
(B) Amino acids
(C) Acetyl CoA
(D) Fatty acids