Question 1

Which of the following best describes the function of the electron transport chain in microbial metabolism?

Accepted Answer

It transfers electrons from NADH and FADH$$_2 to $$oxygen, generating a proton gradient used to produce ATP.

Question 2

A patient is diagnosed with tuberculosis. Which of the following characteristics of Mycobacterium tuberculosis makes it particularly difficult to treat?

Accepted Answer

It has a waxy, mycolic acid-rich cell wall that limits drug penetration.

Question 3

Which of the following equations correctly represents the net reaction of glycolysis?

Accepted Answer

$$\mathrm{C_6H_{12}O_6$} + 2\ \mathrm{NAD^+} + 2\ \mathrm{ADP} + 2\ \mathrm{P_i} \rightarrow 2\ \mathrm{C_3H_4O_3} + 2\ \mathrm{NADH} + 2\ \mathrm{ATP} + 2\ \mathrm{H_2O}$$

Question 4

During a laboratory experiment, a student observes that a bacterial culture grows only at the bottom of a thioglycollate broth tube. What does this indicate about the bacterium?

Accepted Answer

It is an obligate anaerobe.

Question 5

Which of the following best explains why penicillin is more effective against Gram-positive bacteria than Gram-negative bacteria?

Accepted Answer

Gram-positive bacteria have a thicker peptidoglycan layer that is more susceptible to penicillin.

Question 6

A microbiologist is culturing a bacterium that can use nitrate as a terminal electron acceptor in the absence of oxygen. Which metabolic process is being utilized?

Accepted Answer

Anaerobic respiration

Question 7

Which of the following statements about the lac operon in Escherichia coli is correct?

Accepted Answer

The lac operon is induced in the presence of lactose and absence of glucose.

Question 8

A hospital outbreak of Clostridioides difficile is traced to improper sterilization of medical equipment. Which property of C. difficile most likely contributed to its persistence?

Accepted Answer

Production of endospores resistant to heat and disinfectants

Question 9

Which of the following best describes the difference between substrate-level phosphorylation and oxidative phosphorylation?

Accepted Answer

Substrate-level phosphorylation directly transfers a phosphate group to ADP from a phosphorylated intermediate, while oxidative phosphorylation uses a proton gradient to drive ATP synthesis.

Question 10

A patient presents with symptoms of botulism after eating improperly canned food. Which of the following best explains the pathogenesis of this disease?

Accepted Answer

Clostridium botulinum produces a neurotoxin that blocks acetylcholine release at neuromuscular junctions.

Question 11

Which of the following is the correct order of the phases of bacterial growth in a closed batch culture?

Accepted Answer

Lag phase, log (exponential) phase, stationary phase, death phase

Question 12

A researcher is studying a bacterium that grows optimally at 70$$^\circC. $$Which term best describes this organism?

Accepted Answer

Thermophile

Question 13

Which of the following best explains why obligate anaerobes are killed by exposure to oxygen?

Accepted Answer

They lack enzymes such as superoxide dismutase and catalase to detoxify reactive oxygen species.

Question 14

Which of the following equations represents the overall reaction for aerobic respiration in bacteria?

Accepted Answer

$$\mathrm{C_6H_{12}O_6$} + 6\ \mathrm{O_2$} \rightarrow 6\ \mathrm{CO_2$} + 6\ \mathrm{H_2O}$$

Question 15

A patient with a wound infection is found to have a bacterium that grows in the presence and absence of oxygen, but grows better with oxygen. Which term best describes this organism?

Accepted Answer

Facultative anaerobe

Question 16

Which of the following best describes the role of ATP synthase in cellular respiration?

Accepted Answer

It uses the proton motive force to synthesize ATP from ADP and inorganic phosphate.

Question 17

A microbiologist is testing the effect of salt concentration on bacterial growth. Which type of microorganism would be expected to grow best in media containing 15% NaCl?

Accepted Answer

Halophile

Question 18

Which of the following statements about fermentation is correct?

Accepted Answer

Fermentation produces ATP only by substrate-level phosphorylation.

Question 19

A patient is given an antibiotic that inhibits peptidoglycan synthesis. Which of the following would be most affected by this drug?

Accepted Answer

Gram-positive bacteria

Question 20

A bacterial culture is exposed to UV light, resulting in the formation of thymine dimers. Which DNA repair mechanism is most likely to be activated in response?

Accepted Answer

Photoreactivation (light repair)

Reading Equivalencies for Microbiology Exam 3 (Brock Textbook Editions)

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