Question 1

Which of the following best describes the Calvin cycle's role in photosynthesis?

Accepted Answer

It fixes carbon dioxide into organic molecules, producing glucose and regenerating ribulose bisphosphate.

Question 2

Under what condition does oxygenic photophosphorylation switch from noncyclic to cyclic electron flow?

Accepted Answer

When the cell requires more ATP than NADPH.

Question 3

Why do facultative anaerobes like Escherichia coli grow faster in aerobic conditions compared to anaerobic conditions?

Accepted Answer

Aerobic respiration produces more ATP per glucose molecule than anaerobic respiration.

Question 4

How do Cyanobacteria impact the nitrogen cycle in aquatic environments?

Accepted Answer

They fix atmospheric nitrogen into bioavailable forms, supporting primary production.

Question 5

What is the likely effect of extensive tilling on ammonium-based nitrogen fertilizer in soil?

Accepted Answer

It increases the conversion of ammonium to nitrate, making nitrogen more prone to leaching.

Question 6

Which metabolic pathway is favored when electron acceptors are absent?

Accepted Answer

Fermentation

Question 7

The Glyoxylate shunt is important for which metabolic function?

Accepted Answer

Allowing cells to synthesize glucose from fatty acids by bypassing decarboxylation steps of the TCA cycle.

Question 8

Which of the following equations correctly represents the calculation of standard free energy change for a redox reaction?

Accepted Answer

$$\Delta G^\circ' = [-nF] \cdot [\Delta E'^o]$$

Question 9

If $$\Delta G^\circ'$$ for a reaction is negative, what does this imply about the reaction?

Accepted Answer

The reaction is exergonic and will proceed spontaneously.

Question 10

What is the Great Plate Count Anomaly?

Accepted Answer

The observation that most microbes in the environment cannot be cultured using standard laboratory techniques.

Question 11

Which group of bacteria is responsible for anoxygenic photosynthesis using hydrogen sulfide as an electron donor?

Accepted Answer

Purple sulfur bacteria

Question 12

Which process is described by the conversion of atmospheric nitrogen ($$N_2) $$into ammonia ($$NH_3) by $$specialized prokaryotes?

Accepted Answer

Nitrogen fixation

Question 13

Which of the following is an example of an anaplerotic reaction?

Accepted Answer

Conversion of pyruvate to oxaloacetate by pyruvate carboxylase

Question 14

In the context of the redox tower, which reaction would yield the most energy (most negative $$\Delta G^\circ'$$)?

Accepted Answer

Oxidation of $$H_2$$ with $$NO_3$$^-$$ as the electron acceptor

Question 15

Which of the following best describes the difference between exergonic and endergonic reactions?

Accepted Answer

Exergonic reactions release energy ($$\Delta G^\circ'  0)$$

Question 16

Which of the following is a strategy used by microbial ecologists to circumvent the Great Plate Count Anomaly?

Accepted Answer

Using culture-independent methods such as DNA sequencing to assess microbial diversity

Question 17

Which of the following statements about dissimilative sulfur reducers and sulfur oxidizers is correct?

Accepted Answer

Sulfur oxidizers use hydrogen sulfide as an electron donor and produce sulfate.

Question 18

In the light reactions of photosynthesis, what is the primary function of the electron transport chain shown in the diagram?

Accepted Answer

To generate a proton gradient across the thylakoid membrane for ATP synthesis

Question 19

Which label in the photosynthetic electron transport chain diagram corresponds to the site where water is split to release oxygen?

Accepted Answer

Label 4

Question 20

Which of the following best explains why nitrate ($$NO_3$$^-$$) is a more effective electron acceptor than fumarate in anaerobic respiration, as shown in the redox tower?

Accepted Answer

$$NO_3$$^-$$ has a higher (more positive) standard reduction potential (E$$'^o$$) than fumarate, resulting in a larger negative $$\Delta G^\circ'$$ when reduced.

Microbio lecture midterm pt.1

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