Question 1

Which of the following best describes the relationship between catabolism and anabolism in microbial metabolism?

Accepted Answer

Catabolism releases energy by breaking down complex molecules, and this energy is stored as ATP, which is then used by anabolism to build complex molecules from simpler ones.

Question 2

A scientist is studying an enzyme-catalyzed reaction. She increases the temperature from 25°C to 45°C and observes an increase in reaction rate. However, when she raises the temperature to 70°C, the reaction rate drops sharply. What is the most likely explanation for this observation?

Accepted Answer

The enzyme denatures at high temperatures, losing its functional shape and activity.

Question 3

Which of the following equations correctly represents the net ATP yield from glycolysis per molecule of glucose?

Accepted Answer

$$2 \rightarrow 4$$ ATP, net gain $$= 2$$ ATP

Question 4

A patient’s bacterial infection is identified using a mannitol fermentation test. The test medium turns yellow, indicating acid production. What does this result suggest about the bacterium?

Accepted Answer

The bacterium ferments mannitol, producing acidic byproducts.

Question 5

Which of the following best describes the role of oxygen in aerobic respiration?

Accepted Answer

Oxygen is the final electron acceptor, forming water.

Question 6

Which of the following is NOT a correct pairing of enzyme class and function?

Accepted Answer

Isomerases – catalyze the joining of two molecules using ATP

Question 7

A bacterial cell is placed in an environment lacking oxygen but containing nitrate ($$NO_3$$^-$$). The cell continues to generate ATP using an electron transport chain. Which type of respiration is occurring, and what is the final electron acceptor?

Accepted Answer

Anaerobic respiration; $$NO_3$$^-$$

Question 8

Which of the following statements about feedback inhibition is correct?

Accepted Answer

Feedback inhibition occurs when the end product of a metabolic pathway inhibits the first enzyme in the pathway.

Question 9

During the Krebs cycle, which of the following is produced per molecule of glucose?

Accepted Answer

$$2$$ ATP, $$6$$ NADH, $$2$$ $$FADH_2$$, and $$4$$ $$CO_2$$

Question 10

Which of the following best describes a chemoautotroph?

Accepted Answer

An organism that uses chemicals for energy and CO$$_2 as a $$carbon source.

Question 11

A researcher adds a competitive inhibitor to an enzyme-catalyzed reaction. Which of the following best describes the effect on enzyme activity?

Accepted Answer

The inhibitor binds to the active site, preventing substrate binding and decreasing enzyme activity.

Question 12

Which of the following is a correct description of a redox reaction in biological systems?

Accepted Answer

Oxidation is the loss of electrons (often with hydrogen), and reduction is the gain of electrons.

Question 13

Which of the following statements about fermentation is correct?

Accepted Answer

Fermentation produces ATP using an organic molecule as the final electron acceptor.

Question 14

Which of the following is a product of lactic acid fermentation?

Accepted Answer

Lactic acid

Question 15

A mutation causes a bacterium to lack NAD$$^+$$, a coenzyme. Which process would be most directly affected?

Accepted Answer

Oxidation-reduction reactions in glycolysis and the Krebs cycle

Question 16

Which of the following best explains why the electron transport chain produces more ATP in aerobic respiration than in anaerobic respiration?

Accepted Answer

Aerobic respiration uses $$O_2 as $$the final electron acceptor, which allows for a complete electron transport chain and maximum ATP yield.

Question 17

Which of the following is NOT a component of a holoenzyme?

Accepted Answer

Substrate

Question 18

A photoheterotroph obtains its energy and carbon from which sources?

Accepted Answer

Energy from light; carbon from organic compounds

Question 19

Which of the following best describes a ribozyme?

Accepted Answer

An RNA molecule with enzymatic activity

Question 20

A bacterial culture is tested for the presence of cytochrome c oxidase. The test is positive. What does this indicate about the bacterium?

Accepted Answer

It uses the electron transport chain and likely performs aerobic respiration.

Microbial Metabolism: Core Concepts and Pathways

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