Question 1

A patient presents with muscle weakness after ingesting a substance that inhibits actin–myosin interactions. Which cellular process is most directly affected by this inhibition?

Accepted Answer

Cytoplasmic streaming and cell motility

Question 2

A microbiologist is culturing bacteria and observes that the pH of the medium drops from 7.0 to 5.0. By what factor has the hydrogen ion concentration increased?

Accepted Answer

$$10^2$$

Question 3

Which of the following best explains why Gram-negative bacteria are generally more resistant to antibiotics that target peptidoglycan synthesis?

Accepted Answer

They possess an outer membrane that restricts antibiotic entry.

Question 4

A solution contains $$1 	imes 10$$^{-6}$$ M hydrogen ions. What is the pH of this solution?

Accepted Answer

$$6$$

Question 5

Which of the following statements about prions is correct?

Accepted Answer

Prions are infectious proteins that lack nucleic acids.

Question 6

A patient is diagnosed with malaria caused by Plasmodium. Which of the following best describes Plasmodium's lifestyle?

Accepted Answer

Obligate intracellular parasite

Question 7

A bacterial culture has a generation time of 30 minutes. If you start with 1 cell, how many cells will there be after 3 hours, assuming unlimited resources?

Accepted Answer

$$2^6 = 64$

Question 8

Which of the following best describes the structure of a phospholipid in a cell membrane?

Accepted Answer

A hydrophilic head and two hydrophobic tails

Question 9

A clinical sample is stained and observed under a microscope. The cells appear purple after Gram staining. What can you infer about the cell wall structure?

Accepted Answer

The cells have a thick peptidoglycan layer.

Question 10

Which of the following is a key difference between bacterial and mitochondrial DNA?

Accepted Answer

Both are circular, but mitochondrial DNA is inherited maternally in most eukaryotes.

Question 11

A patient is treated with a drug that disrupts tubulin polymerization. Which eukaryotic structure is most likely to be affected?

Accepted Answer

Flagella with a 9+2 microtubule arrangement

Question 12

Which of the following best describes antigenic shift in viruses?

Accepted Answer

A major change in viral genome due to reassortment of gene segments

Question 13

A microbiologist performs a serial dilution and plates 0.1 mL of a $$10^{-4}$$ dilution, resulting in 50 colonies. What is the original concentration of bacteria in CFU/mL?

Accepted Answer

$$5 	imes 10^6$ CFU/mL

Question 14

Which of the following best explains why buffers are important in biological systems?

Accepted Answer

They maintain a stable pH by neutralizing added acids or bases.

Question 15

Which of the following is a distinguishing feature of Archaea compared to Bacteria?

Accepted Answer

Archaea have ether-linked membrane lipids.

Question 16

A fungus is identified in a clinical sample. Which of the following characteristics would help distinguish it from a protozoan?

Accepted Answer

Presence of chitin in the cell wall

Question 17

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

Accepted Answer

It inhibits the growth of some organisms while allowing others to grow.

Question 18

A patient is infected with a virus that establishes a persistent infection. Which of the following best describes this type of infection?

Accepted Answer

The virus remains in the host for long periods, sometimes with intermittent symptoms.

Question 19

Which of the following best explains why pleomorphic bacteria can be challenging to identify in clinical microbiology?

Accepted Answer

They can vary in shape and size, making them difficult to classify based on morphology.

Question 20

Which of the following best describes the role of sterols in eukaryotic cell membranes?

Accepted Answer

They help maintain membrane fluidity and stability.

Introductory Microbiology: Study Guide for Exam 1 (Chapters 2, 3, 4, 6, 7)

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