Question 1

Which of the following best explains why endospores are highly resistant to heat and chemical damage?

Accepted Answer

They contain dipicolinic acid complexed with Ca$$^{2+}$$, which stabilizes DNA and proteins.

Question 2

A bacterium is found to move toward a source of glucose in its environment. Which mechanism is primarily responsible for this behavior?

Accepted Answer

Chemotaxis

Question 3

Which of the following statements about the electron transport chain (ETC) in bacteria is correct?

Accepted Answer

The ETC generates a proton motive force by pumping protons across the cytoplasmic membrane.

Question 4

A culture of E. coli is grown in a batch culture. After several hours, the number of viable cells begins to decrease. Which phase of the growth curve is this?

Accepted Answer

Decline (death) phase

Question 5

Which of the following best describes the main function of the pentose phosphate pathway in bacteria?

Accepted Answer

To produce NADPH and ribose-5-phosphate for biosynthesis

Question 6

A bacterium isolated from deep ocean sediments is able to orient and migrate along Earth's magnetic field lines. Which cellular inclusion is responsible for this behavior?

Accepted Answer

Magnetosomes

Question 7

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

Accepted Answer

$$2 \ \mathrm{ATP}$$

Question 8

A researcher is using a spectrophotometer to measure the growth of a bacterial culture. Which property is being measured, and what is its relationship to cell number?

Accepted Answer

Optical density; it is approximately proportional to the total cell number (both live and dead)

Question 9

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 10

Which of the following statements about the endosymbiotic theory is supported by evidence?

Accepted Answer

Mitochondria and chloroplasts divide by binary fission and have circular DNA.

Question 11

A bacterium is classified as a chemolithoautotroph. Which of the following best describes its metabolic strategy?

Accepted Answer

It uses inorganic compounds as an energy source and CO$$_2 as a $$carbon source.

Question 12

During aerobic respiration, which molecule serves as the terminal electron acceptor in the electron transport chain?

Accepted Answer

O$$_2$$

Question 13

Which of the following best describes substrate-level phosphorylation?

Accepted Answer

ATP is generated by the direct transfer of a phosphate group from a high-energy substrate to ADP.

Question 14

A bacterial culture is grown in a chemostat. Which of the following statements is true about this system?

Accepted Answer

Cell density and substrate concentration remain constant at steady state.

Question 15

Which of the following is a correct statement about the energy yield of fermentation compared to aerobic respiration?

Accepted Answer

Fermentation yields less ATP per glucose molecule than aerobic respiration.

Question 16

A microbiologist wants to isolate a bacterium that can grow in the presence of oxygen but does not use it for respiration. Which type of organism should she look for?

Accepted Answer

Aerotolerant anaerobe

Question 17

Which of the following best explains why psychrophilic bacteria have more unsaturated fatty acids in their membranes?

Accepted Answer

Unsaturated fatty acids increase membrane fluidity at low temperatures.

Question 18

A student is preparing a culture medium to isolate a specific bacterium from a mixed sample. She adds a dye that changes color if the bacterium ferments lactose. What type of medium is she using?

Accepted Answer

Differential medium

Question 19

Which of the following equations correctly represents the calculation of generation time ($$g) $$during exponential growth?

Accepted Answer

$$g = \frac{t}{n}$$, \ where \ t \ is \ time \ and \ n \ is \ number \ of \ generations$

Question 20

A disk diffusion assay is performed to test the effectiveness of an antimicrobial agent. What does a large zone of inhibition around the disk indicate?

Accepted Answer

The agent is highly effective at inhibiting microbial growth.

Microbiology Exam 2 Study Guide: Cell Structure, Metabolism, Growth, and Control

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