Question 1

Which of the following best describes the function of a buffer in a biological system?

Accepted Answer

A buffer maintains pH by absorbing excess H$$^+ or OH$^-$$ ions without neutralizing all acids.

Question 2

How do salts and sugars help preserve foods?

Accepted Answer

They create a hypertonic environment, causing microbial cells to lose water by osmosis.

Question 3

Which biosafety level (BSL) is most appropriate for an introductory Microbiology laboratory?

Accepted Answer

BSL-1

Question 4

Which of the following best describes aerotolerant anaerobes?

Accepted Answer

They do not use oxygen but can tolerate its presence.

Question 5

Most bacteria reproduce by which process?

Accepted Answer

Binary fission

Question 6

During which phase of the bacterial growth curve do bacteria adapt to new environmental conditions without increasing in number?

Accepted Answer

Lag phase

Question 7

A medium that contains a dye that inhibits Gram-positive bacteria and a sugar that turns yellow when fermented is best described as:

Accepted Answer

Both selective and differential

Question 8

Generation time in bacteria is defined as:

Accepted Answer

The time required for a bacterial population to double in number.

Question 9

Facultative halophiles are best described as organisms that:

Accepted Answer

Can grow in the presence or absence of high salt concentrations.

Question 10

Which of the following would be a valid method to measure metabolic activity in a growing bacterial culture?

Accepted Answer

Measuring glucose consumption over time.

Question 11

In a thioglycollate broth tube, where would you expect to see the growth of a microaerophile?

Accepted Answer

Just below the surface, where oxygen concentration is lower than atmospheric.

Question 12

What is the function of the enzyme catalase in bacteria?

Accepted Answer

It breaks down hydrogen peroxide into water and oxygen: $$2H_2O_2 \rightarrow 2H_2O + O_2$

Question 13

Biofilms are best described as:

Accepted Answer

Communities of microorganisms attached to a surface and embedded in a self-produced matrix.

Question 14

Which of the following is an example of a surface where biofilms commonly form?

Accepted Answer

Teeth (dental plaque)

Question 15

Which enzyme is responsible for joining Okazaki fragments during DNA replication?

Accepted Answer

DNA ligase

Question 16

Which enzyme copies DNA to make a molecule of RNA?

Accepted Answer

RNA polymerase

Question 17

After UV radiation damages DNA, which repair mechanism is most commonly used by bacteria?

Accepted Answer

Nucleotide excision repair

Question 18

Which of the following best describes feedback inhibition in enzyme regulation?

Accepted Answer

The end product of a metabolic pathway inhibits an earlier enzyme in the pathway.

Question 19

Which of the following is NOT a method of genetic exchange in bacteria?

Accepted Answer

Binary fission

Question 20

Which of the following is the most effective concentration range of ethanol for disinfection?

Accepted Answer

60–90\%

Microbiology Exam 2 Study Guide – Step-by-Step Guidance

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