Question 1

Which of the following best distinguishes a viroid from a virus?

Accepted Answer

Viroids lack a protein coat and consist solely of a small, circular, single-stranded RNA molecule.

Question 2

A patient is diagnosed with Creutzfeldt-Jakob disease after brain surgery. Which property of the infectious agent makes standard sterilization procedures ineffective?

Accepted Answer

The infectious agent is a misfolded protein that is highly resistant to heat, radiation, and common disinfectants.

Question 3

During which phase of the bacterial growth curve are cells most susceptible to antibiotics that target cell wall synthesis?

Accepted Answer

Exponential (log) phase

Question 4

Which of the following equations correctly describes the number of bacterial cells ($$N) $$after $$n$$ generations, starting from an initial population ($$N_0$$)?

Accepted Answer

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

Question 5

A culture starts with 5 bacterial cells and has a generation time of 40 minutes. How many cells will there be after 2 hours of growth?

Accepted Answer

40 cells

Question 6

Which of the following best explains why obligate anaerobes are killed by oxygen?

Accepted Answer

They lack enzymes such as catalase to detoxify reactive oxygen species.

Question 7

A bacterium grows best at 37°C but can survive between 10°C and 45°C. What is the optimum growth temperature for this organism?

Accepted Answer

37°C

Question 8

Which of the following is a correct match between organism type and its temperature preference?

Accepted Answer

Thermophile: prefers high temperatures, such as hot springs

Question 9

Which of the following statements about prion diseases is correct?

Accepted Answer

The infectious form is a misfolded protein that can induce misfolding in normal proteins.

Question 10

A facultative anaerobe is streaked on two plates: one incubated in oxygen, the other in anoxic conditions. What is the expected result?

Accepted Answer

Robust growth in oxygen, but some growth in anoxic conditions.

Question 11

Which of the following best describes the process of binary fission in bacteria?

Accepted Answer

A mother cell doubles in size, replicates its genome, and divides into two genetically identical daughter cells.

Question 12

Which of the following is a key difference between viroids and prions?

Accepted Answer

Viroids are infectious RNA molecules, while prions are infectious proteins.

Question 13

Which of the following environmental factors is most likely to affect the conformation and function of bacterial enzymes?

Accepted Answer

Temperature

Question 14

A bacterial culture is in stationary phase. Which of the following best describes what is happening?

Accepted Answer

The rate of cell growth equals the rate of cell death due to nutrient depletion and waste accumulation.

Question 15

Which of the following is a common misconception about the destruction of prions?

Accepted Answer

Prions are resistant to most common sterilization methods.

Question 16

Which of the following best explains why viroids must enter plant cells through a wound?

Accepted Answer

Viroids lack a protein coat and cannot bind to cell surface receptors.

Question 17

Which of the following is a toxic byproduct of oxygen metabolism that can damage cellular macromolecules?

Accepted Answer

Hydrogen peroxide ($$H_2O_2)$$

Question 18

A newly discovered microorganism grows optimally at 90°C and is found in deep-sea hydrothermal vents. How should it be classified?

Accepted Answer

Hyperthermophile

Question 19

Which of the following best describes the relationship between environmental preferences and pathogen survival?

Accepted Answer

Pathogens must be able to tolerate and adapt to the environmental conditions of their host to survive and cause disease.

Question 20

Which of the following is true regarding the spread of prion diseases between species?

Accepted Answer

Spread is linked to the similarity of the amino acid sequences of prion proteins between species.

Acellular Infectious Agents and Microbial Growth: Study Guide

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