Question 1

Which of the following best describes the main purpose of the Calvin cycle in photosynthetic organisms?

Accepted Answer

To fix carbon dioxide into organic molecules and regenerate ribulose bisphosphate

Question 2

During oxygenic photophosphorylation, when does cyclic photophosphorylation occur instead of noncyclic photophosphorylation?

Accepted Answer

When the cell needs to produce more ATP than NADPH

Question 3

Why do facultative anaerobes like *E. 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 for other organisms

Question 5

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

Accepted Answer

It increases the rate of nitrification, leading to more nitrate formation and potential loss from the soil

Question 6

Which metabolic pathway is favored when there is a lack of external electron acceptors?

Accepted Answer

Fermentation

Question 7

The Glyoxylate shunt is important for which of the following reasons?

Accepted Answer

It allows cells to convert fatty acids into carbohydrates

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 releases energy

Question 10

Which of the following best describes an anaplerotic reaction?

Accepted Answer

A reaction that replenishes intermediates of the TCA cycle

Question 11

The Great Plate Count Anomaly refers to which of the following observations?

Accepted Answer

The number of cells observed microscopically is much higher than the number that can be cultured

Question 12

Which group of bacteria is responsible for oxygenic photosynthesis?

Accepted Answer

Cyanobacteria

Question 13

In the context of the redox tower (see $$image_1$$), which reaction would yield the most energy for a cell?

Accepted Answer

$$\mathrm{H}_2 + \mathrm{NO}_3^- \rightarrow \mathrm{NO}_2^- + \mathrm{H}_2O$$

Question 14

Which of the following is a key product of biological nitrogen fixation?

Accepted Answer

Ammonia ($$\mathrm{NH}_3)$$

Question 15

Which of the following best describes the difference between dissimilative sulfur reducers and dissimilative sulfur oxidizers?

Accepted Answer

Sulfur reducers use sulfur as an electron acceptor, while sulfur oxidizers use it as an electron donor

Question 16

In the light reactions of photosynthesis (see $$image_2$$), what is the primary function of the ATP synthase complex?

Accepted Answer

To synthesize ATP from ADP and inorganic phosphate using the proton gradient

Question 17

Which process is favored when a cell lacks external electron acceptors and why?

Accepted Answer

Fermentation, because it relies on substrate-level phosphorylation

Question 18

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

Accepted Answer

Carboxylation of pyruvate to oxaloacetate

Question 19

Which of the following statements about exergonic and endergonic reactions is correct?

Accepted Answer

Exergonic reactions have a negative $$\Delta G$$ and release energy

Microbiology Midterm Study Guide: Metabolism, Photosynthesis, Nitrogen Cycle, and Microbial Ecology

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