Cellular Respiration Practice Exam with Answers


A 23-questions practice exam with answers on cellular respiration steps including glycolysis, the citric acid cycle and the electron transport chain.

Question 1

List the standard reduction potential values, including appropriate signs and units.

(A)  Cytochrome f (Fe3+) / Cytochrome f (Fe2+)

(B)  Ferredoxin (Fe3+) / Ferredoxin (Fe2+)

(C)  Cytochrome b (Fe3+) / Cytochrome b (Fe2+)

Question 2

Each redox couple listed in Question #1 is written as oxidized/reduced (oxidized form on the left and reduced form on the right).

True /False

Question 3

Which chemical listed in Question #1 has the greatest electron affinity?

Question 4

If, under standard biochemical conditions, cytochrome b donated an electron to ferredoxin, then (select any/all answers that apply):

  • the coupled redox reaction would be exergonic.
  • the coupled redox reaction would be endergonic.
  • the coupled redox reaction would have a negative ΔG’° value.
  • cytochrome b (Fe3+) would become reduced to cytochrome b (Fe2+) during the coupled redox reaction.
  • cytochrome b (Fe2+) would become oxidized to cytochrome b (Fe3+) during the coupled redox reaction.

Question 5

Which of the following species could potentially act as an electron donor? Select any/all answers that apply.

  • cytochrome b (Fe2+)
  • cytochrome b (Fe3+)
  • cytochrome f (Fe2+)
  • cytochrome f (Fe3+)
  • ferredoxin (Fe2+)

Question 6

Which of the following species is in an oxidized form?  Select any/all answers that apply.

  1. cytochrome b (Fe2+)
  2. cytochrome b (Fe3+)
  3. cytochrome f (Fe2+)
  4. cytochrome f (Fe3+)
  5. ferredoxin (Fe2+)

Question 7

Use two of the given redox couples to create a complete, balanced redox reaction for which ΔG’° is the most exergonic it can be (for the forward reaction).

(A)  Cytochrome f (Fe3+) / Cytochrome f (Fe2+)
(B)  Ferredoxin (Fe3+) / Ferredoxin (Fe2+)
(C)  Cytochrome b (Fe3+) / Cytochrome b (Fe2+)

Question 8

Calculate the ΔE’° value for the redox reaction you’ve just created in Question #7. Show all mathematical work and indicate appropriate units.

Question 9

Now calculate the ΔG’° value for your redox reaction.  Show all mathematical work and indicate appropriate units.

Question 10

Now calculate the K’eq for your redox reaction.  Show all mathematical work and indicate appropriate units.

Question 11

Your calculated values for ΔE’°, ΔG’°, and/or K’eq mean that the redox reaction you originally wrote (Question #7) will proceed spontaneously in the forward direction.

True /False

Question 12

Suppose you’re in charge of creating a “mock mitochondrial electron transport chain”.  Your synthetic mitochrondria will exploit the same ATP synthesis strategy that endogenous mitochondria do, except that the only electron carriers you have at your disposal are the three redox couples listed in Question #1.  Electrons will be initially handed over to your mock transport chain via a new universal electron carrier, called NOVA, that has a standard reduction potential (E’°) of -0.566 volts.  As usual, the final electron acceptor will be molecular oxygen.  Assuming standard biochemical conditions, we would expect electrons to move in the following order:

Cytochrome f (Fe3+) / Cytochrome f (Fe2+)           0.365 V

Cytochrome b (Fe3+) / Cytochrome b (Fe2+)       0.077 V

Ferredoxin (Fe3+) / Ferredoxin (Fe2+)                 -0.432 V

Nova (ox) /Nova (red)                                            -0.566 V

begins by donating one electron to , which then transfers that electron to , which then transfers that electron to , which then hands off that electron to .

Per this scenario,  electrons (simply indicate the total number) must be carried down the chain in order for one molecule of O2 to be reduced to two molecules of water.

Question 13

Anabolic processes commonly use the free energy provided by __________ and/or __________ in order to drive the synthesis of biological macromolecules.

  • Pi; NADPH
  • ADP; NADP+
  • ATP; NAD+

 Question 14


  • transfers electrons in reductive biosynthesis.
  • in its oxidized form is NADH.
  • accepts 2 electrons and 2 hydrogen ions.
  • accepts 2 electrons and 1 hydrogen ion.
  • accepts 1 electron and 1 hydrogen ion.

Question 15

Which of the following processes results in the net production of ATP or GTP? Select any/all answers that apply.

  • cycling of the F0F1-ATP synthase
  • citric acid cycle
  • glycolysis
  • gluconeogenesis
  • glycogenesis

Question 16

Which of the following processes harnesses free energy in the form of reducing equivalents? Choose all answers that apply.

  • pentose phosphate pathway
  • citric acid cycle
  • glycolysis
  • gluconeogenesis
  • glycogenesis

Question 17

Which species would most readily donate its electron(s)?

  • Water
  • ubiquinol
  • H2
  • NADH

Question 18

Name one allosteric activator of the glycolytic enzyme PFK-1 (phosphofructokinase-1): ____

Name one enzymatic step of the gluconeogenic pathway wherein universal reducing equivalents are lost: ___
Name one enzyme of the gluconeogenic pathway that catalyzes a hydrolysis reaction:
Name one enzyme of the TCA cycle that catalyzes a substrate-level phosphorylation: ___
Name one enzyme complex of the electron transport chain that uses iron-sulfur centers to shuttle electrons: ____

Question 19

Name one enzyme of glycolysis that catalyzes an essentially irreversible step:
Name one enzymatic step of the gluconeogenic pathway that constitutes a phosphoryl group transfer: ____
Name one enzymatic step of the TCA cycle wherein a universal electron carrier (in its reduced form) is a product of the reaction: _____

Question 20

Questions #20 & 21 refer to Step #10 of glycolysis (catalyzed by pyruvate kinase) and Step #5 of the TCA cycle (catalyzed by succinyl-CoA synthetase).
These two metabolic steps are similar in that (select any/answers that apply):

  • both are redox reactions.
  • both are essentially irreversible under typical cellular conditions.
  • both are hydrolysis reactions.
  • both are substrate-level phosphorylations.
  • both harness energy in the form of universal reducing equivalents.

Question 21

Which of the following species acts as the phosphoryl group donor in one or both metabolic steps?  Select any/all answers that apply

  • succinyl-CoA
  • GDP
  • succinate
  • pyruvate
  • phosphoenolpyruvate

Question 22

The enzyme _____ is the only membrane-bound enzyme of the TCA cycle that is also a component of the mitochondrial electron transport chain.

Question 23

Fill in the blanks about each of the following sequential steps of the electron transfer chain (ETC) of the inner mitochondrial membrane.
The initial electron donor of the ETC is ___, which hands its two electrons off to FMN, within Complex I.

Electrons from both Complex I and Complex II are ultimately donated to the same molecule _____.

Within Complex III, electrons from ubiquinol are ultimately donated to ____, which then passes those electrons on to Complex IV. ____ is the final electron acceptor of the ETC. The downhill movement of electrons through the ETC creates a proton gradient across the inner mitochondrial membrane. The ___ subunit of the ATP synthase creates a channel that allows for the downhill movement of protons from the inter-membrane space to the matrix; the concomitant release of free energy drives the synthesis of ATP by the ___ subunit of that same protein.

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