Question 1

Which of the following best describes the role of the terminal electron acceptor in microbial respiration?

Accepted Answer

It accepts electrons from the electron transport chain, becoming reduced in the process.

Question 2

During aerobic respiration of glucose in E. coli, which molecule acts as the electron donor and what is its oxidized waste product?

Accepted Answer

Glucose; carbon dioxide

Question 3

Which of the following equations correctly relates the change in Gibbs free energy ($$\Delta G) to $$standard free energy change ($$\Delta G^\circ) $$and the activity quotient ($$Q$$)?

Accepted Answer

$$\Delta G = \Delta G^\circ + RT \ln(Q)$$

Question 4

A chemolithotroph is defined as an organism that:

Accepted Answer

Uses inorganic compounds as electron donors for energy.

Question 5

Which of the following statements about anaerobic respiration is TRUE?

Accepted Answer

It uses a terminal electron acceptor other than oxygen.

Question 6

In the context of the redox tower, which combination would yield the most energy for a microorganism?

Accepted Answer

Using a strong electron donor and a strong electron acceptor.

Question 7

Which of the following is NOT a synonym for the electron donor in respiration?

Accepted Answer

Oxidant

Question 8

A bacterium in an anoxic marine sediment is using sulfate ($$SO_4$$^{2-}$$) as its terminal electron acceptor. This process is best described as:

Accepted Answer

Anaerobic respiration

Question 9

Which of the following best explains why chemical gradients form in microenvironments such as sediments?

Accepted Answer

Because the rates of biogeochemical processes often exceed the rates of diffusion, leading to steep gradients.

Question 10

Which of the following is a correct example of a chemolithotrophic reaction?

Accepted Answer

$$H_2$$ + \frac{1}{2}$$O_2$$ \rightarrow H_2O$$

Question 11

Which of the following is TRUE regarding the products of assimilatory versus dissimilatory metabolism of inorganic compounds?

Accepted Answer

Dissimilatory metabolism produces reduced products that are excreted.

Question 12

A microorganism oxidizes hydrogen gas ($$H_2) $$and reduces nitrate ($$NO_3$$^-$$) in the absence of oxygen. Which terms best describe this organism’s metabolism?

Accepted Answer

Chemolithotroph performing anaerobic respiration

Question 13

Which of the following is a plausible reason why hydrogen gas ($$H_2) is a $$common electron donor for chemolithotrophs in hydrothermal vent ecosystems?

Accepted Answer

Hydrogen gas is produced abiotically and is highly diffusive, making it readily available.

Question 14

Which of the following best describes the function of hydrogenase in hydrogen-oxidizing bacteria?

Accepted Answer

It splits $$H_2$$ into $$2H^+$$ and $$2e^-$$, enabling electron flow into the electron transport chain.

Question 15

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

Accepted Answer

Oxygen ($$O_2)$$

Question 16

A microorganism is found to use $$Fe^{2+} as an $$electron donor and $$O_2 as a $$terminal electron acceptor. Which of the following best describes its metabolism?

Accepted Answer

Chemolithotrophic aerobic respiration

Question 17

Which of the following statements about the redox tower is correct?

Accepted Answer

The best electron acceptors are found at the bottom left of the tower.

Question 18

In a scenario where both oxygen and nitrate are available as terminal electron acceptors, which will a facultative anaerobe use first and why?

Accepted Answer

Oxygen, because it is a stronger electron acceptor and yields more energy.

Question 19

Which of the following best explains why anaerobic respiration is important in sediment environments?

Accepted Answer

Oxygen is rapidly depleted, so microorganisms must use alternative terminal electron acceptors.

Respiration in Microorganisms: Chemolithotrophy & Anaerobic Respiration

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