Question 1

Which of the following best describes the main function of bacteriorhodopsin in halophilic archaea?

Accepted Answer

It acts as a light-driven proton pump to generate a proton motive force.

Question 2

In the oxygenic Z pathway of photosynthesis, what is the ultimate electron donor and what is the ultimate electron acceptor?

Accepted Answer

Water is the electron donor and NADP+ is the electron acceptor.

Question 3

Which process is responsible for generating ATP in both phototrophic and respiratory electron transport systems?

Accepted Answer

ATP synthase driven by the proton motive force

Question 4

A bacterium living in an anaerobic environment uses nitrate as a terminal electron acceptor. Which of the following reduction reactions is most likely to occur?

Accepted Answer

$$\mathrm{NO_3$^- \rightarrow NO_2$^-}$$

Question 5

Which of the following equations correctly represents the relationship between the electrical potential and pH difference components of the proton motive force?

Accepted Answer

$$\Delta p = \Delta \Psi - 60 \Delta pH$$

Question 6

Which of the following is NOT a function driven by the proton motive force in bacteria?

Accepted Answer

Synthesis of ribosomal RNA

Question 7

A mutation disables the cytochrome component of a bacterium’s electron transport system. Which of the following is the most immediate consequence?

Accepted Answer

The cell cannot efficiently transfer electrons to the terminal electron acceptor.

Question 8

Which of the following best explains why metal-reducing bacteria form electrically conductive pili (nanowires)?

Accepted Answer

To transfer electrons to insoluble or distant electron acceptors such as Fe(III) oxides.

Question 9

In cyclic photophosphorylation (as seen in Photosystem II of purple nonsulfur bacteria), what is the fate of the excited electron?

Accepted Answer

It returns to bacteriochlorophyll after passing through the electron transport system.

Question 10

Which of the following is a correct sequence of events in the bacterial respiratory electron transport system?

Accepted Answer

Substrate dehydrogenase transfers electrons to quinone, which then transfers electrons to a terminal oxidase complex.

Question 11

A bacterial fuel cell is constructed using a biofilm of Geobacter species. What is the primary role of the anode in this system?

Accepted Answer

It receives electrons from the bacteria, creating a charge separation.

Question 12

Which of the following statements about anaerobic respiration in prokaryotes is TRUE?

Accepted Answer

It uses terminal electron acceptors other than oxygen, such as nitrate or sulfate.

Question 13

Which of the following best describes the role of NADH in the electron transport system?

Accepted Answer

It donates electrons to the substrate oxidoreductase, initiating electron flow.

Question 14

A bacterium is found in a lake sediment where oxygen is depleted but nitrate is available. Which process is most likely to occur?

Accepted Answer

Denitrification, reducing nitrate to nitrogen gas

Question 15

Which of the following is a direct product of the terminal oxidase complex in aerobic respiration?

Accepted Answer

$$\mathrm{H_2O}$$

Question 16

Which of the following best explains why the proton motive force is essential for bacterial survival?

Accepted Answer

It powers ATP synthesis and drives essential cellular processes such as nutrient uptake and flagellar rotation.

Question 17

Which of the following is a plausible consequence if a bacterium’s environment becomes depleted of all terminal electron acceptors?

Accepted Answer

The electron transport system will halt, and ATP synthesis via oxidative phosphorylation will cease.

Question 18

Which of the following is a correct description of the function of quinone in the bacterial electron transport system?

Accepted Answer

It acts as a mobile electron carrier between protein complexes.

Question 19

Which of the following best describes the process of denitrification?

Accepted Answer

The sequential reduction of nitrate to nitrogen gas.

Microbial Electron Flow and Metabolism: Phototrophy, Respiration, and Bioelectricity

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