Cell Biology Questions and Answers – Aerobic Respiration – Proton Motive Force


This set of Cell Biology Multiple Choice Questions & Answers (MCQs) focuses on “Aerobic Respiration – Proton Motive Force”.

1. The free energy released during electron transport is utilized to move protons from _____________ to inner membrane and cytosol.
a) extracellular environment
b) outer membrane
c) nucleus
d) matrix
View Answer

Answer: d
Explanation: The free energy released in the electron transport moves protons from matrix to inner membrane and cytosol of the mitochondrion.

2. Proton motive force is the net sum of how many gradient components?
a) 1
b) 2
c) 3
d) 4
View Answer

Answer: b
Explanation: Proton motive force is a measure of electrochemical gradient. Because the translocation of protons across the membrane lead to a difference of hydrogen ion concentration and a difference of charge, the energy present in both components of the proton electrochemical gradient are combined and expressed as proton motive force.

3. The contribution made by electric potential versus pH gradient to the proton motive force (Δp) is determined by which property of the mitochondrial membrane?
a) thickness
b) position in the cell
c) permeability
d) number of cristae
View Answer

Answer: c
Explanation: The contribution made by electric potential versus pH gradient is determined by the permeability of the membrane. For example if at a particular instance, membrane is permeable to Cl- ions the electric potential gradient is reduced without affecting the proton gradient.

4. The approximate proton motive force of an actively respiring mitochondrion is ____________ mV.
a) 220
b) 240
c) 260
d) 280
View Answer

Answer: a
Explanation: The approximate proton motive force that an actively respiring mitochondrion generates across its inner membrane is 220 mV. In mammalian mitochondria, 80 percent is represented by the voltage component and 20 percent by proton concentration.

5. The maintenance of proton motive force requires that inner mitochondrial membrane remains permeable to protons.
a) True
b) False
View Answer

Answer: b
Explanation: The inner mitochondrial membrane must remain highly impermeable to protons otherwise the gradient established by electron transport would be quickly dissipated by the leakage of protons back into the matrix.

6. For which organelle proton motive force is also a source of energy?
a) nucleus
b) ribosomes
c) mitochondrion
d) golgi complex
View Answer

Answer: c
Explanation: Other than hydrolysis of ATP, mitochondrion has alternate sources of energy one of which is proton motive force. It drives the uptake of ADP in exchange of ATP; and can also be used to pull calcium ions into the mitochondrion.

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