Question 1

Which of the following statements best describes the relationship between energy and entropy in living systems?

Accepted Answer

Energy is the ability to do work, and entropy is a measure of disorder or randomness in a system.

Question 2

Given the equation for Gibbs free energy change: $$\Delta G = \Delta H - T\Delta S$$, which condition will always result in a spontaneous reaction?

Accepted Answer

$$\Delta H  0$$

Question 3

Which of the following best explains why ATP is considered a 'medium-sized' energy carrier in cells?

Accepted Answer

ATP hydrolysis releases less energy than the hydrolysis of phosphoenolpyruvate or 1,3-bisphosphoglycerate.

Question 4

A bacterium is found to use light as an energy source, CO$$_2 as a $$carbon source, and inorganic molecules as electron donors. Which set of prefixes best describes its metabolism?

Accepted Answer

Photoautolithotroph

Question 5

Which of the following reactions is most likely to be catalyzed by an enzyme in a living cell?

Accepted Answer

A reaction with a high activation energy barrier and a negative $$\Delta G$$

Question 6

Which of the following is a correct description of the fate of pyruvate under anaerobic conditions in fermentation?

Accepted Answer

Pyruvate is reduced to fermentation products such as lactic acid or ethanol.

Question 7

Which of the following best explains why NADH carries more energy than ATP?

Accepted Answer

NADH can donate electrons to the electron transport chain, resulting in more ATP synthesis.

Question 8

A patient’s stool sample is tested with a pH indicator and turns yellow, indicating acid production. What does this result suggest about the metabolic activity of the microbe?

Accepted Answer

The microbe is fermenting the substrate, producing acidic byproducts.

Question 9

Which of the following is a unique feature of the glyoxylate bypass compared to the TCA cycle?

Accepted Answer

It allows cells to grow on acetate or fatty acids by bypassing the decarboxylation steps.

Question 10

Which of the following best describes the main difference between fermentation and respiration?

Accepted Answer

Fermentation does not use an exogenous terminal electron acceptor, while respiration does.

Question 11

Which pathway produces both NADH and NADPH during glucose catabolism?

Accepted Answer

Entner-Doudoroff (ED) pathway

Question 12

Which of the following is a real-world example of microbial syntrophy?

Accepted Answer

Two microbes cooperate to degrade a petroleum contaminant that neither can degrade alone, resulting in a negative $$\Delta G$$ for the overall reaction.

Question 13

Which of the following is the central intermediate in the aerobic catabolism of aromatic compounds such as benzoate?

Accepted Answer

Catechol

Question 14

Which of the following best explains why the ability to digest porphyrans is limited to certain populations in Japan?

Accepted Answer

Horizontal gene transfer from marine microbes to gut microbes, combined with consumption of raw seaweed, enables this ability.

Question 15

Which of the following is NOT a product of the TCA cycle per pyruvate oxidized?

Accepted Answer

2 ATP

Question 16

Which of the following best describes the role of enzymes in metabolic reactions?

Accepted Answer

Enzymes lower the activation energy, allowing reactions to proceed more rapidly.

Question 17

Which of the following is a correct net reaction for the conversion of pyruvate to acetyl-CoA by the pyruvate dehydrogenase complex?

Accepted Answer

$$	ext{Pyruvate} + 	ext{NAD}^+ + 	ext{CoA} ightarrow 	ext{Acetyl-CoA} + 	ext{CO}_2 + 	ext{NADH} + 	ext{H}^+$$

Question 18

Which of the following is a function of the TCA cycle in addition to energy production?

Accepted Answer

Synthesis of amino acid precursors such as $$\alpha-$$ketoglutarate and oxaloacetate.

Microbial Metabolism: Energetics and Catabolism (Chapter 13 Study Notes)

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