BIOC 384 EXAM 4 QUESTION AND
ANSWERS RATED A+ 2025/2026
Explain why a mutation in pyruvate carboxylase that blocks its ability to be
regulated by acetyl-CoA results in lower rates of energy conversion via the Citrate Cycle. - correct
answer ✔Oxaloacetate becomes limiting, reducing the rate of acetyl-CoA oxidation, which inhibits
citrate cycle flux.
To make high levels of citrate for the production of commercial grade citric acid, Pfizer modified
culture conditions and used a special strain of Aspergillus niger to maximize fermentation. What two
processes need to be inhibited in order to ensure the rate of citrate secretion exceeds citrate
catabolism? - correct answer ✔citrate cycle flux and the citrate lyase reaction
The figure at the right shows the iron-sulfur cluster in the enzyme aconitase
that facilitates the conversion of citrate to isocitrate in reaction 2 of the citrate cycle. Which
of the following statements is true regarding this Fe-S cluster? - correct answer ✔The Fe-S cluster
coordinates an OH removal and a hydration reaction
Identify the correct order of electron
transfers in the electron transport system starting
with FADH2. Answers are shown to the right. - correct answer ✔Complex II--> Complex III-->
Cytochrome C--> Complex IV
Which one of the statements below
best describes the mechanism of proton
translocation by the Electron Transport System using a redox loop mechanism exemplified by the Q
cycle? - correct answer ✔A redox reaction separating protons and electrons within complex III of the
electron transport system,
, with the protons translocated to the inter-membrane space and the electrons used to reduce Q.
Which protein in the electron transport system listed in the
box to the right functions as diffusible soluble protein? - correct answer ✔Cytochrome C
Given a pH gradient differential measured across the inner
mitochondrial membrane of an aquatic animal is found to be 25 times lower inside the mitochondrial
matrix as compared to the inter-membrane space, what is the energy
requirement (DG) to transport 1 H+ across the membrane, from the mitochondrial matrix
side to the inter-membrane space, at 10ºC with a membrane potential of 50 mV? - correct answer
✔+12.4 kJ/mol
What mechanism moves electrons from cytosolic NADH to the mitochondrial matrix? - correct answer
✔malate-aspartate shuttle
What is another physiological reaction that is catalyzed by the cytochrome c oxidase complex of
the electron transport system besides the oxidation of cytochrome c? - correct answer ✔Reduction of
molecular oxygen to H2O
A pressurized insecticide sprayer works by building up internal pressure using a
hand pump to fill the airtight container with air. The spray nozzle distributes liquid by holding
down the control button, which opens the nozzle. To clean out the sprayer, you must release
the internal pressure by opening the release valve on the side. Choose the best term from the
box to answer the questions below.
(a) The proton gradient is the insecticide solvent.
(b) The ATP synthase is the spray nozzle.
ANSWERS RATED A+ 2025/2026
Explain why a mutation in pyruvate carboxylase that blocks its ability to be
regulated by acetyl-CoA results in lower rates of energy conversion via the Citrate Cycle. - correct
answer ✔Oxaloacetate becomes limiting, reducing the rate of acetyl-CoA oxidation, which inhibits
citrate cycle flux.
To make high levels of citrate for the production of commercial grade citric acid, Pfizer modified
culture conditions and used a special strain of Aspergillus niger to maximize fermentation. What two
processes need to be inhibited in order to ensure the rate of citrate secretion exceeds citrate
catabolism? - correct answer ✔citrate cycle flux and the citrate lyase reaction
The figure at the right shows the iron-sulfur cluster in the enzyme aconitase
that facilitates the conversion of citrate to isocitrate in reaction 2 of the citrate cycle. Which
of the following statements is true regarding this Fe-S cluster? - correct answer ✔The Fe-S cluster
coordinates an OH removal and a hydration reaction
Identify the correct order of electron
transfers in the electron transport system starting
with FADH2. Answers are shown to the right. - correct answer ✔Complex II--> Complex III-->
Cytochrome C--> Complex IV
Which one of the statements below
best describes the mechanism of proton
translocation by the Electron Transport System using a redox loop mechanism exemplified by the Q
cycle? - correct answer ✔A redox reaction separating protons and electrons within complex III of the
electron transport system,
, with the protons translocated to the inter-membrane space and the electrons used to reduce Q.
Which protein in the electron transport system listed in the
box to the right functions as diffusible soluble protein? - correct answer ✔Cytochrome C
Given a pH gradient differential measured across the inner
mitochondrial membrane of an aquatic animal is found to be 25 times lower inside the mitochondrial
matrix as compared to the inter-membrane space, what is the energy
requirement (DG) to transport 1 H+ across the membrane, from the mitochondrial matrix
side to the inter-membrane space, at 10ºC with a membrane potential of 50 mV? - correct answer
✔+12.4 kJ/mol
What mechanism moves electrons from cytosolic NADH to the mitochondrial matrix? - correct answer
✔malate-aspartate shuttle
What is another physiological reaction that is catalyzed by the cytochrome c oxidase complex of
the electron transport system besides the oxidation of cytochrome c? - correct answer ✔Reduction of
molecular oxygen to H2O
A pressurized insecticide sprayer works by building up internal pressure using a
hand pump to fill the airtight container with air. The spray nozzle distributes liquid by holding
down the control button, which opens the nozzle. To clean out the sprayer, you must release
the internal pressure by opening the release valve on the side. Choose the best term from the
box to answer the questions below.
(a) The proton gradient is the insecticide solvent.
(b) The ATP synthase is the spray nozzle.
