Question 1

Which of the following best describes the role of the electron transport chain (ETC) in bacterial cells?

Accepted Answer

It transfers electrons from NADH and FADH2 to oxygen, creating a proton gradient used to generate ATP.

Question 2

During oxidative phosphorylation, what is the primary function of ATP synthase?

Accepted Answer

To use the proton motive force to synthesize ATP from ADP and inorganic phosphate ($$ADP + P_i \rightarrow ATP).$$

Question 3

Which of the following is NOT a component of the proton motive force (PMF) in bacteria?

Accepted Answer

Concentration gradient of sodium ions ($$Na^+)$$

Question 4

A bacterium is unable to generate enough ATP because its electron transport chain is disrupted. Which of the following is the most likely consequence?

Accepted Answer

The cell will accumulate NADH and lack sufficient NAD$$^+$$ for glycolysis.

Question 5

In cyclic photophosphorylation, which molecule acts as the final electron acceptor?

Accepted Answer

The original reaction center chlorophyll

Question 6

Which process allows bacteria to survive in environments lacking oxygen by regenerating NAD$$^+$$ from NADH?

Accepted Answer

Fermentation

Question 7

A mutation disables Complex IV in the mitochondrial electron transport chain. What is the most direct effect?

Accepted Answer

Electrons cannot be transferred to oxygen, halting ATP production via oxidative phosphorylation.

Question 8

Which of the following best explains why bacteria use alternative electron acceptors in anaerobic respiration?

Accepted Answer

To allow ATP production when oxygen is unavailable by transferring electrons to molecules like nitrate ($$NO_3$$^-$$) or sulfate (SO_4$^{2-}).$$

Question 9

Which of the following is a unique characteristic of nitrogen-fixing bacteria?

Accepted Answer

They convert atmospheric nitrogen ($$N_2) $$into ammonia ($$NH_3) $$using the enzyme nitrogenase.

Question 10

In the nitrogen cycle, which process is responsible for converting ammonia ($$NH_3) $$into nitrate ($$NO_3$$^-$$)?

Accepted Answer

Nitrification

Question 11

A farmer applies nitrogen fertilizer to a field. Which group of bacteria is primarily responsible for converting this ammonia into nitrate, making it available to plants?

Accepted Answer

Nitrifying bacteria

Question 12

Which of the following is a consequence of excessive denitrification in agricultural soils?

Accepted Answer

Loss of nitrogen to the atmosphere as $$N_2$$ gas, reducing soil fertility.

Question 13

Which of the following is TRUE regarding the role of decomposer bacteria in the nitrogen cycle?

Accepted Answer

They break down organic matter, releasing ammonia ($$NH_3) $$into the soil.

Question 14

A patient is diagnosed with iron-deficiency anemia. Which microbial process could be affected in pathogens infecting this patient?

Accepted Answer

Electron transport chain activity, as iron is a cofactor in cytochromes.

Question 15

Which of the following best describes the difference between cyclic and non-cyclic photophosphorylation in photosynthetic bacteria?

Accepted Answer

Cyclic photophosphorylation involves electrons returning to the original reaction center, producing only ATP; non-cyclic transfers electrons to NADP$$^+$$, producing both ATP and NADPH.

Question 16

Which of the following is a common electron donor in bacterial electron transport chains?

Accepted Answer

NADH

Question 17

A bacterium is growing in an environment with limited oxygen and switches to using sulfate ($$SO_4$$^{2-}$$) as its terminal electron acceptor. What type of respiration is this?

Accepted Answer

Anaerobic respiration

Question 18

Which of the following is a direct result of the proton gradient established by the electron transport chain?

Accepted Answer

Synthesis of ATP via ATP synthase ($$ADP + P_i \rightarrow ATP)$$

Question 19

In the nitrogen cycle, which process returns nitrogen to the atmosphere?

Accepted Answer

Denitrification

Microbial Bioenergetics and Nitrogen Cycle: Study Notes

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