Question 1

Which of the following best explains why small cell size is advantageous for microbes?

Accepted Answer

Small cells have a higher surface area-to-volume ratio, which enhances nutrient uptake and waste elimination.

Question 2

A microbiologist wants to observe the detailed internal structure of a bacterial cell. Which type of microscopy should they use?

Accepted Answer

Transmission electron microscopy (TEM)

Question 3

Which of the following statements correctly distinguishes between Gram-positive and Gram-negative bacterial cell envelopes?

Accepted Answer

Gram-positive bacteria have a thick peptidoglycan layer and no outer membrane, while Gram-negative bacteria have a thin peptidoglycan layer and an outer membrane.

Question 4

Which laboratory technique is used to differentiate between Gram-positive and Gram-negative bacteria?

Accepted Answer

Gram staining

Question 5

Which of the following best describes the endosymbiotic theory?

Accepted Answer

Mitochondria and chloroplasts originated from free-living prokaryotes that were engulfed by ancestral eukaryotic cells.

Question 6

A bacterium is found to be motile using a flagellum. Which of the following statements correctly compares prokaryotic and eukaryotic flagella?

Accepted Answer

Prokaryotic flagella rotate like a propeller, while eukaryotic flagella move in a whip-like fashion.

Question 7

Which of the following equations represents the calculation of exponential microbial growth, where $$N is $$the final cell number, $$N_0 is $$the initial cell number, and $$n is $$the number of generations?

Accepted Answer

$$N = N_0$ 	imes 2^n$$

Question 8

A researcher is studying a bacterium that can grow in the presence or absence of oxygen, but grows better with oxygen. How should this organism be classified?

Accepted Answer

Facultative anaerobe

Question 9

Which of the following best describes the function of the proton motive force ($$\Delta p) in $$microbial cells?

Accepted Answer

It is used to drive ATP synthesis, flagellar rotation, and active transport.

Question 10

Which of the following statements about fermentation and respiration is correct?

Accepted Answer

Fermentation achieves redox balance by transferring electrons to organic molecules, while respiration uses an external electron acceptor.

Question 11

A scientist is measuring the number of viable bacteria in a sample using the plate count method. Which of the following is a limitation of this technique?

Accepted Answer

It only counts cells that are able to grow and form colonies under the given conditions.

Question 12

Which of the following best describes a biofilm?

Accepted Answer

A complex community of microorganisms attached to a surface and embedded in a self-produced matrix.

Question 13

Which of the following statements about viruses is correct?

Accepted Answer

Viruses are obligate intracellular parasites because they require host cell machinery for replication.

Question 14

During the lytic cycle of a T4 bacteriophage, which step immediately follows attachment to the host cell?

Accepted Answer

Penetration of the viral genome into the host cell

Question 15

Which of the following best explains why prokaryotes can perform coupled transcription and translation, but eukaryotes cannot?

Accepted Answer

Prokaryotes lack a nuclear membrane, allowing ribosomes to access mRNA as it is being transcribed.

Question 16

Which of the following is NOT a function of chaperone proteins in bacteria?

Accepted Answer

Catalyzing peptide bond formation during translation

Question 17

Which of the following best describes the difference between negative and positive control of transcription in bacteria?

Accepted Answer

Negative control involves repressors that inhibit transcription, while positive control involves activators that enhance transcription.

Question 18

A bacterial strain is unable to synthesize the amino acid tryptophan and requires it to be supplied in the growth medium. What is this strain called, and which screening method would you use to detect it?

Accepted Answer

Auxotroph; replica plating

Question 19

Which of the following is a correct description of the three major mechanisms of horizontal gene transfer in bacteria?

Accepted Answer

Transformation involves uptake of naked DNA, transduction involves bacteriophages, and conjugation involves direct cell-to-cell contact.

Question 20

A point mutation changes a codon from $$	ext{GAA} ($$glutamic acid) to $$	ext{GAG} ($$also glutamic acid). What type of mutation is this, and what property of the genetic code allows this to occur?

Accepted Answer

Silent mutation; the degeneracy of the genetic code

MCB3020 Microbiology Midterm Study Guide – Step-by-Step Guidance

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