Mitochondria MCQ Questions and Answers for Practice

1. In the mitochondria NADH and QH₂ are essentially oxidized by ...............since it is the terminal electron acceptor.

1. carbon dioxide
2. ozone
3. hydrogen peroxide
4. oxygen

2. The................is between the inner and outer membranes of the mitochondria.

1. ATP synthase complex
2. intermembrane space
3. matrix
4. intracellular fluid

3. Oxidative phosphorylation requires all of the items listed below except

1. the flow of electrons from NADH and QH₂ in the membrane.
2. a matrix more positively charged than the intermembrane space.
3. a terminal electron acceptor which is H₂O in mitochondria.
4. ATP synthase in the correct position in the membrane.

4. ATP synthase is located in the...................of the mitochondrion.

1. intermembrane space
2. outer membrane
3. matrix
4. inner membrane

5. The inner mitochondrial membrane contributes to the formation of a proton gradient mainly because it

1. is rich in proteins.
2. is not rich in proteins.
3. is the location of specific transporter proteins.
4. is a barrier to protons.

6. The chemiosmotic theory is a concept that

1. the transport of Na⁺ and K⁺ across cell membranes is by active transport
2. explains how transport by facilitated diffusion reaches a saturation limit
3. a proton gradient that drives the formation of ATP
4. explains the blood-brain barrier

7. The protonmotive force is a result of

1. the flow of protons within the inner mitochondrial membrane
2. a combination of an electrical potential and a chemical potential
3. the flow of electrons from the matrix to the inner membrane space
4. All of the above

8. At one time the uncoupler 2, 4-dinitrophenol was used as a weight reducing drug. Its side-effects, including death, resulted in its discontinued use. How could this drug cause weight loss?

1. The uncoupler is an allosteric activator of ATP synthase. This increases the rate of translocation of H⁺ and the oxidation of fuels, including fats.
2. The uncoupler allows the oxidation of fats from adipose tissue without the production of ATP. This allows the oxidation to proceed continuously and use up the fats.
3. The uncoupler inhibits the transport of pyruvate into the matrix of the mitochondria. Fats are then degraded to glycerol and subsequently to pyruvate to provide the necessary energy. Thereby depleting fat stores.
4. The uncoupler causes ATP to be produced at a much higher rate than normal and this causes weight loss.

9. What feature of cytochromes makes them valuable in electron transport systems?

1. aspartate residues in the active site
2. the multiple alpha-helices
3. the porphyrin ring
4. the iron ion

10. Which has the highest reduction potential?

1. complex I
2. O₂
3. complex II
4. NADH

11. To reduce one molecule of O₂, ..............electron(s) must be passed through the electron transport chain and ..............molecule(s) of NADH is(are) oxidized.

1. 1, 1
2. 4, 4
3. 1, 2
4. 4, 2

12. Which is a component of complex I?

1. FMN
2. FAD
3. TPP
4. Q

13. How many protons are translocated across the membrane by complex I for every pair of electrons that are passed from NADH to QH₂?

1. 1
2. 2
3. 3
4. 4

14. Which complex in the electron transport chain does not contribute to the proton gradient?

1. I
2. II
3. III
4. IV

15. The terminal electron acceptor for complex III of the electron transport chain is

1. Fe-S
2. Q
3. FAD
4. cytochrome C