Question 1

Which of the following best describes the role of magnesium (Mg) in prokaryotic cells?

Accepted Answer

It acts as a cofactor for certain enzymatic reactions and is an inorganic cellular cation.

Question 2

A bacterium that uses light as an energy source, CO$$_2 as a $$carbon source, and inorganic compounds as a reducing power source is classified as a:

Accepted Answer

Photolithoautotroph

Question 3

Which of the following equations correctly calculates the number of generations ($$n) in a $$bacterial culture, given an initial cell number $$N_0$$ and a final cell number $$N_t$$?

Accepted Answer

$$n = \log_{10} N_t - \log_{10} N_0$

Question 4

A culture medium that contains beef extract and yeast extract, but not all components are chemically defined, is best described as:

Accepted Answer

Complex medium

Question 5

Which of the following adaptations would you expect to find in a thermophilic bacterium living in a hot spring?

Accepted Answer

Synthesis of isozymes that are resistant to thermal denaturation

Question 6

Which of the following best explains why oxygen can be both beneficial and harmful to prokaryotic cells?

Accepted Answer

Oxygen is a great electron acceptor but can form reactive species that damage cellular components.

Question 7

A bacterium that grows only in the absence of oxygen and is killed by its presence is classified as a:

Accepted Answer

Strict anaerobe

Question 8

Which of the following is a function of the Min proteins in *E. coli* cell division?

Accepted Answer

They facilitate the correct placement of the FtsZ ring for septation.

Question 9

A culture medium that contains bile salts and crystal violet to inhibit Gram-positive bacteria, and lactose plus a pH indicator to distinguish fermenters, is best described as:

Accepted Answer

Selective and differential medium

Question 10

Which of the following equations gives the growth rate constant ($$k) in $$generations per unit time?

Accepted Answer

$$k = n / t$$

Question 11

A bacterium isolated from the Dead Sea requires 20% NaCl for growth. Which term best describes this organism?

Accepted Answer

Halophilic

Question 12

Which of the following best describes the function of NAD (nicotinamide adenine dinucleotide) in microbial metabolism?

Accepted Answer

It is an electron carrier involved in redox reactions.

Question 13

Which of the following is a likely adaptation of a psychrophilic bacterium?

Accepted Answer

Unsaturated fatty acids in the membrane

Question 14

A bacterial culture starts with $$1 	imes 10^3$ cells and grows to 1$$ 	imes $$10^6$$ cells in 5 hours. What is the generation time ($$g) in $$hours? Use $$n = \log_{10}(N_t/N_0$)$$ and $$g = t/n.$$

Accepted Answer

1.67 hours

Question 15

Which of the following best explains why optical density (OD) measurements can be misleading when estimating microbial growth?

Accepted Answer

OD is affected by cell size and shape, so it may not accurately reflect cell number.

Question 16

Which of the following is a trace element required by some enzymes for nitrogen assimilation in prokaryotes?

Accepted Answer

Molybdenum (Mo)

Question 17

Which of the following best describes the effect of increasing temperature on the solubility of oxygen in water?

Accepted Answer

Solubility decreases

Question 18

Which of the following best describes the function of FtsZ in bacterial cell division?

Accepted Answer

It forms a ring at the future site of septum formation and recruits other division proteins.

Question 19

A bacterium that can grow in the presence or absence of oxygen, but does not use oxygen in its metabolism, is classified as a(n):

Accepted Answer

Aerotolerant anaerobe

Question 20

Which of the following best describes the role of compatible solutes in microbial cells?

Accepted Answer

They help cells avoid losing water under osmotic stress.

Lectures 14, 15

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