Question 1

Which of the following statements best describes binary fission in prokaryotes?

Accepted Answer

It is a symmetric cell division resulting in two genetically identical daughter cells.

Question 2

During binary fission, which protein is primarily responsible for forming the division ring at the cell's midpoint?

Accepted Answer

FtsZ

Question 3

A bacterial culture starts with $$1 	imes 10^3$ cells. If the generation time is 30 minutes, how many cells will there be after 2 hours of exponential growth?

Accepted Answer

$$1.6 	imes 10^4$

Question 4

Which of the following best explains why the slope of the line on a semi-logarithmic plot of cell number versus time represents the growth rate during exponential growth?

Accepted Answer

Because exponential growth appears as a straight line on a semi-log plot, and the slope is proportional to the rate of cell division.

Question 5

A researcher is using a Petroff-Hausser counting chamber to estimate bacterial cell numbers. Which of the following is a major limitation of this method?

Accepted Answer

It cannot distinguish between live and dead cells.

Question 6

Which of the following best describes the function of selective media in microbiology?

Accepted Answer

It contains compounds that allow only certain organisms to grow while inhibiting others.

Question 7

A culture medium contains a dye that turns colonies green if they ferment lactose. What type of medium is this?

Accepted Answer

Differential medium

Question 8

Which of the following environmental factors is most likely to affect the fluidity of microbial cell membranes and the rate of enzymatic reactions?

Accepted Answer

Temperature

Question 9

A bacterium that grows optimally at 37°C but can also grow at 4°C is best described as a:

Accepted Answer

Psychrotolerant organism

Question 10

Which of the following best explains why halophiles can survive in high-salt environments?

Accepted Answer

They accumulate compatible solutes to balance osmotic pressure.

Question 11

Which enzyme is responsible for converting hydrogen peroxide ($$H_2O_2) $$into water and oxygen in aerobic bacteria?

Accepted Answer

Catalase

Question 12

A facultative anaerobe is best described as an organism that:

Accepted Answer

Can grow in the presence or absence of oxygen, using aerobic respiration when oxygen is available.

Question 13

Which of the following equations correctly calculates the number of generations ($$n) $$that have occurred during bacterial growth?

Accepted Answer

$$n = \frac{\log N - \log N_0$}{\log 2}$$

Question 14

A culture of E. coli is grown in a batch culture. After a period of rapid cell division, the number of viable cells plateaus. Which phase of growth is this?

Accepted Answer

Stationary phase

Question 15

Which of the following is a key advantage of using a spectrophotometer to monitor microbial growth?

Accepted Answer

It allows rapid estimation of cell density without disturbing the culture.

Question 16

A mutant strain of bacteria with a nonfunctional FtsZ protein would most likely:

Accepted Answer

Fail to divide and form long filamentous cells.

Question 17

Which of the following best describes the role of superoxide dismutase in aerobic microorganisms?

Accepted Answer

It converts superoxide radicals ($$O_2$$^-$$) into hydrogen peroxide (H_2O_2$).

Question 18

Which of the following best explains why jams and jellies are resistant to microbial spoilage?

Accepted Answer

Their high sugar content creates low water activity, inhibiting most microbial growth.

Question 19

A microbiologist wants to isolate a bacterium that can grow in the presence of 10% NaCl. Which term best describes this organism?

Accepted Answer

Halophile

Question 20

Which of the following is a correct statement about the maintenance of internal pH in neutrophilic bacteria?

Accepted Answer

They maintain their cytoplasmic pH near neutrality even when external pH varies.

Exam 2 (Lecture 8) Microbial Growth: Mechanisms, Measurement, and Influencing Factors (Ch 4, Sections 4.1–4.16)

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