Question 1

Which of the following best describes the difference between sterilization and disinfection?

Accepted Answer

Sterilization removes all living microbes, while disinfection only kills pathogenic microbes.

Question 2

A hospital wants to sterilize heat-sensitive plastic syringes. Which method is most appropriate?

Accepted Answer

Ethylene oxide gas sterilization

Question 3

Which of the following equations represents the reaction catalyzed by catalase to detoxify hydrogen peroxide?

Accepted Answer

$$2H_2O_2 \rightarrow 2H_2O + O_2$

Question 4

A bacterium that grows optimally at 37\degree C but can survive between 20\degree C and 45\degree C is classified as a:

Accepted Answer

Mesophile

Question 5

Which of the following best explains why 100% ethanol is less effective as a disinfectant than 70% ethanol?

Accepted Answer

Water is required to denature proteins effectively.

Question 6

Which of the following is the correct order of microbial resistance to chemical biocides, from most resistant to least resistant?

Accepted Answer

Prions \u003e Bacterial endospores \u003e Mycobacteria \u003e Gram-negative bacteria \u003e Enveloped viruses

Question 7

A bacterium is found growing only at the bottom of a thioglycollate broth tube. What is its oxygen requirement?

Accepted Answer

Obligate anaerobe

Question 8

Which of the following statements about halophiles is correct?

Accepted Answer

Extreme halophiles maintain a high internal solute concentration to resist plasmolysis.

Question 9

Which of the following best describes the mechanism of action of penicillins?

Accepted Answer

Inhibit cell wall synthesis by preventing cross-linkage of NAM subunits

Question 10

A patient is infected with a Gram-negative bacterium that produces beta-lactamase. Which antibiotic is most likely to be ineffective?

Accepted Answer

Penicillin G

Question 11

Which of the following best explains why sulfonamides are selectively toxic to bacteria but not to humans?

Accepted Answer

Humans obtain folic acid from their diet, while bacteria must synthesize it.

Question 12

Which of the following is a limitation of using an autoclave for sterilization?

Accepted Answer

Oily substances are not effectively sterilized.

Question 13

Which of the following best describes the effect of ultraviolet (UV) light on microbial DNA?

Accepted Answer

It causes adjacent thymine bases to dimerize, disrupting DNA replication.

Question 14

A food company wants to preserve pickles using salt and vinegar. Which type of microorganism would be least affected by this method?

Accepted Answer

Extreme halophiles

Question 15

Which of the following best describes the principle of selective toxicity?

Accepted Answer

A drug kills or inhibits the pathogen without harming the host.

Question 16

Which of the following mechanisms is NOT a common way bacteria acquire antibiotic resistance?

Accepted Answer

Absorbing antibiotics from the environment

Question 17

Which of the following best explains why pasteurization is used for milk?

Accepted Answer

It reduces microbial growth and eliminates pathogenic bacteria without significantly affecting taste.

Question 18

Which of the following is a correct equation for the superoxide dismutase (SOD) reaction?

Accepted Answer

$$O_2$$^- + $$O_2^- + 2H$$^+ \rightarrow H_2O_2 + $$O_2$$

Question 19

Which of the following best describes the action of heavy metals such as silver on microbes?

Accepted Answer

They react with proteins, disrupting microbial metabolism.

Microbial Controls: Physical and Chemical Factors Affecting Microbial Growth

Study Guide - Practice Questions