Question 1

Which of the following best describes the main function of the electron transport chain in cellular respiration?

Accepted Answer

To transfer electrons from NADH and FADH$_2$ to oxygen, creating a proton gradient used to generate ATP

Question 2

During oxidative phosphorylation, what is the primary role of the proton gradient across the inner mitochondrial membrane?

Accepted Answer

To drive the synthesis of ATP by ATP synthase

Question 3

Which of the following is NOT a possible fate of an electron after it is excited by light energy in a photosynthetic organism?

Accepted Answer

Direct conversion into ATP

Question 4

In the nitrogen cycle, which process is responsible for converting atmospheric N$_2$ into ammonia (NH$_3$)?

Accepted Answer

Nitrogen fixation

Question 5

Which of the following best explains why purple sulfur bacteria do NOT generate oxygen during photosynthesis?

Accepted Answer

They use hydrogen sulfide (H$_2$S) as an electron donor instead of water

Question 6

Which of the following is a correct description of cyclic photophosphorylation?

Accepted Answer

Electrons cycle back to the same photosystem, generating ATP but not NADPH or O$_2$

Question 7

A patient is infected with a bacterium that can survive in the presence of oxygen but does not use it for growth. Which term best describes this organism?

Accepted Answer

Aerotolerant anaerobe

Question 8

Which of the following bacterial structures is most directly involved in conjugation and horizontal gene transfer?

Accepted Answer

Pilus

Question 9

Which of the following is a high-level disinfectant that can inactivate spores with prolonged exposure?

Accepted Answer

Chlorine compounds

Question 10

A hospital is choosing a disinfectant for surfaces that may be contaminated with Mycobacterium tuberculosis. Which property is most important for the disinfectant to have?

Accepted Answer

Ability to disrupt mycolic acids in cell walls

Question 11

Which of the following best describes the role of ATP synthase in the electron transport chain?

Accepted Answer

It uses the proton gradient to synthesize ATP from ADP and inorganic phosphate

Question 12

Which of the following is a common terminal electron acceptor in anaerobic respiration?

Accepted Answer

NO$_3^-$ (nitrate)

Question 13

Which of the following statements about denitrification is correct?

Accepted Answer

It reduces nitrate to nitrogen gas, returning nitrogen to the atmosphere

Question 14

A researcher is studying a bacterium that can use both organic and inorganic electron donors for energy. Which term best describes this organism?

Accepted Answer

Mixotroph

Question 15

Which of the following is a reason why Gram-negative bacteria are generally more resistant to disinfectants than Gram-positive bacteria?

Accepted Answer

They possess an outer membrane that limits entry of many chemicals

Question 16

Which of the following best explains why green sulfur bacteria cannot use water as an electron donor?

Accepted Answer

They lack the necessary enzymes to split water

Question 17

A sample is treated with a disinfectant that destroys lipid membranes but does not inactivate spores. Which level of disinfection is this?

Accepted Answer

Intermediate-level disinfection

Question 18

Which of the following is a unique feature of Mycobacterium species that makes them resistant to many disinfectants?

Accepted Answer

High lipid content (mycolic acids) in their cell wall

Question 19

Which of the following best describes the process of ammonification in the nitrogen cycle?

Accepted Answer

Conversion of organic nitrogen to ammonia

Question 20

A bacterium is found to use Fe$^{2+}$ (ferrous iron) as an electron donor and O$_2$ as an electron acceptor. Which type of metabolism is this?

Accepted Answer

Chemoautotrophy (chemolithotrophy)

Microbiology Study Guide: Bioenergetics, Nitrogen Cycle, and Disinfection

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