Q: A culture starts with $$N_0 = 500$ cells and grows for 3 generations. What is the final population (N_t$)? Use N_t$$ = $$N_0$$ \times 2^n$$.

$$N_t = 500 \times 2^3$ = 4000$$

Question 1

Which of the following best describes the difference between antigenic drift and antigenic shift in Influenza A viruses?

Accepted Answer

Antigenic drift refers to small, gradual mutations over time, while antigenic shift refers to major genetic changes due to reassortment.

Question 2

A patient is diagnosed with a viral infection and prescribed ribavirin. Which mechanism best explains how ribavirin acts against viruses?

Accepted Answer

It mimics normal nucleotides, causing premature termination of RNA synthesis by blocking RNA polymerase.

Question 3

Which formula would you use to calculate the number of generations ($$n) $$that have occurred in a bacterial culture, given an initial population ($$N_0) $$and a final population ($$N_t$$)?

Accepted Answer

$$n = \frac{\log(N_t/N_0$)}{\log 2} $$

Question 4

During which phase of the bacterial growth curve are cells most susceptible to antibiotics?

Accepted Answer

Log (exponential) phase

Question 5

Which of the following statements about the naming system for Influenza viruses is correct?

Accepted Answer

Only Influenza A uses the H and N subtype naming system.

Question 6

A microbiologist wants to sterilize glassware. Which method is most appropriate?

Accepted Answer

Dry heat

Question 7

Which of the following best describes the relationship between normal microbiota and the host in mutualism?

Accepted Answer

Both the microbiota and the host benefit.

Question 8

Which site in the human body is typically considered sterile under normal conditions?

Accepted Answer

Lower respiratory tract

Question 9

A patient with HIV is prescribed azidothymidine (AZT). What is the primary mechanism of action for AZT?

Accepted Answer

It inhibits reverse transcriptase, preventing viral DNA synthesis.

Question 10

Which of the following is NOT a correct match between microbial control method and its primary use?

Accepted Answer

Boiling — sterilization

Question 11

A culture starts with $$N_0 = 500$ cells and grows for 3 generations. What is the final population (N_t$)? Use N_t$$ = $$N_0$$ 	imes 2^n$$.

Accepted Answer

$$N_t = 500 	imes 2^3$ = 4000$$

Question 12

Which of the following best describes an opportunistic pathogen?

Accepted Answer

It causes disease when host defenses are compromised or normal microbiota are disrupted.

Question 13

Which microbial group is most likely to grow in refrigerated foods and potentially cause spoilage?

Accepted Answer

Psychrotrophs

Question 14

Which term describes the process of reducing microbial load to safe levels, but not necessarily eliminating all microorganisms?

Accepted Answer

Decontamination

Question 15

A yeast cell reproduces by budding. Which statement best describes this process?

Accepted Answer

A new cell grows from the parent cell and eventually detaches.

Question 16

Which oxygen profile describes a microorganism that can grow with or without oxygen, but prefers oxygen when available?

Accepted Answer

Facultative anaerobe

Question 17

Which chemical agent is most effective for sterilizing heat-sensitive medical equipment?

Accepted Answer

Ethylene oxide

Question 18

Which phase of the bacterial growth curve is characterized by equal rates of cell division and cell death?

Accepted Answer

Stationary phase

Question 19

Which of the following is a correct match between pH group and environment?

Accepted Answer

Neutrophiles — neutral pH environments

Question 20

Which statement about antibiotics and antiviral drugs is correct?

Accepted Answer

Vaccination is the most effective method of preventing viral infections.

Microbiology Study Notes: Viruses, Microbial Growth, Control, and Host–Microbe Interactions

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