Question 1

Which of the following statements best describes the main function of the citric acid cycle (Krebs cycle) in microbial metabolism?

Accepted Answer

It completely oxidizes pyruvate to CO$_2$ and generates NADH and FADH$_2$ for ATP production.

Question 2

During aerobic respiration in bacteria, what is the total ATP yield per glucose molecule, and which process is responsible for the majority of this ATP?

Accepted Answer

38 ATP, produced mainly by oxidative phosphorylation via the electron transport chain.

Question 3

Which of the following is NOT a possible terminal electron acceptor in anaerobic respiration?

Accepted Answer

Oxygen (O$_2$)

Question 4

In the electron transport chain, what is the main consequence of transferring electrons through a series of carriers with increasingly positive reduction potentials?

Accepted Answer

Protons are pumped across the membrane, creating a proton motive force ($\Delta p$).

Question 5

Which equation correctly represents the oxidation of NADH during cellular respiration?

Accepted Answer

$\mathrm{NADH} \rightarrow \mathrm{NAD}^+ + 2e^- + H^+$

Question 6

A bacterium is growing in an environment where only nitrate (NO$_3^-$) is available as a terminal electron acceptor. Compared to aerobic respiration, what is the expected ATP yield and why?

Accepted Answer

Lower ATP yield because nitrate has a less positive reduction potential than oxygen.

Question 7

Which process is responsible for the majority of ATP synthesis during aerobic respiration in bacteria?

Accepted Answer

Oxidative phosphorylation driven by the proton motive force ($\Delta p$) across the membrane.

Question 8

Which of the following best explains why fermentation yields much less ATP than respiration?

Accepted Answer

Fermentation does not use an electron transport chain or generate a proton motive force.

Question 9

In a competitive environment with limited glucose, which microorganism would likely outcompete the others for energy production?

Accepted Answer

An aerobic bacterium using oxygen as the terminal electron acceptor.

Question 10

Which of the following is a correct summary of the products generated per glucose molecule during the citric acid cycle?

Accepted Answer

6 CO$_2$, 8 NADH, 2 FADH$_2$, 2 ATP

Question 11

What is the role of ATP synthase in bacterial cells?

Accepted Answer

It uses the proton gradient across the membrane to convert ADP and inorganic phosphate into ATP.

Question 12

Which of the following best describes the fate of pyruvate during fermentation?

Accepted Answer

It is reduced to various organic compounds to regenerate NAD$^+$.

Question 13

Which equation represents the overall redox reaction for NAD$^+$ reduction?

Accepted Answer

$\mathrm{NAD}^+ + 2e^- + H^+ \rightarrow \mathrm{NADH}$

Question 14

Which of the following is TRUE regarding substrate-level phosphorylation?

Accepted Answer

It directly transfers a phosphate group from a substrate to ADP to form ATP.

Question 15

Which of the following is a characteristic of the electron transport chain in prokaryotes?

Accepted Answer

It is associated with the cytoplasmic membrane and involves a series of redox reactions.

Question 16

Which of the following best explains why only prokaryotes can perform anaerobic respiration using electron acceptors such as nitrate or sulfate?

Accepted Answer

Eukaryotes lack the necessary enzymes and membrane systems to use these acceptors.

Question 17

A bacterium produces butanol, acetone, CO$_2$, and H$_2$ from hexose fermentation. Which genus is most likely responsible for this metabolic activity?

Accepted Answer

Clostridium acetobutylicum

Question 18

Which of the following is a correct description of chemolithotrophy?

Accepted Answer

It uses inorganic compounds as electron donors for energy production.

Question 19

Which of the following is TRUE about the proton motive force ($\Delta p$) in bacterial cells?

Accepted Answer

It is generated by the movement of protons across the membrane during electron transport.

Question 20

Which of the following statements best distinguishes aerobic respiration from fermentation?

Accepted Answer

Aerobic respiration uses an electron transport chain and a terminal electron acceptor, while fermentation does not.

Microbial Metabolism: Catabolic Pathways and Energy Generation

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