Brock Biology of Microorganisms 2025
Quiz and Assessment Workbook
Filtration can result in sterilization of serum and blood products
A. by removing viruses.
B. by relying on gravity.
C. by removing toxins.
D. using high heat and filtration.
✅ Correct answer: A. by removing viruses
Rationale: Filtration works by physically removing microorganisms, including viruses, from
heat-sensitive solutions. It doesn’t rely on heat or remove toxins. Gravity alone is not sufficient
for sterilization.
_____ is a control method that removes microorganisms rather than inhibiting or killing
them.
A. Boiling
B. Sterilization
C. Radiation
D. Filtration
E. Disinfection
✅ Correct answer: D. Filtration
Rationale: Filtration removes microbes without killing or inhibiting them, unlike boiling,
disinfection, or sterilization which destroy microorganisms.
Which of the following is not a factor that affects germicidal activity?
A. the material being treated
B. the length of exposure
C. the strength of the germicide
D. the microorganism being treated
E. All of these are factors.
✅ Correct answer: E. All of these are factors.
Rationale: Each listed variable influences the effectiveness of a germicide; therefore, all are
relevant factors.
All of the following pertain to hypochlorites except
A. release hypochlorous acid in solution.
B. cause denaturation of enzymes.
,C. found in iodophors.
D. used to disinfect water, restaurant, and medical equipment.
E. found in common household bleach.
✅ Correct answer: C. found in iodophors.
Rationale: Iodophors contain iodine, not hypochlorite. Hypochlorites are chlorine compounds
used for disinfection and enzyme denaturation.
_____ is a halogen used in gaseous and liquid form for large-scale disinfection of drinking
water and sewage.
A. Iodine
B. Chlorine
C. Bromine
D. Fluorine
E. All of the choices are correct.
✅ Correct answer: B. Chlorine
Rationale: Chlorine is the main halogen used in water and sewage treatment due to its strong
oxidizing and germicidal properties.
The compound that is an organic base containing chlorine and two phenolic rings...
A. carbolic acid.
B. chlorhexidine.
C. triclosan.
D. formalin.
E. quaternary ammonium compounds.
✅ Correct answer: B. chlorhexidine
Rationale: Chlorhexidine is used for skin disinfection and mucous membrane cleaning; it
contains chlorinated aromatic rings and is broad-spectrum.
Alcohols
A. dissolve membrane lipids at concentrations greater than 50%.
B. can be used for disinfection or antisepsis.
C. are skin degerming agents.
D. are limited in effectiveness due to rapid evaporation.
E. All of the choices are correct.
✅ Correct answer: E. All of the choices are correct.
Rationale: All statements describe alcohol’s properties — it dissolves lipids, removes microbes
from skin, and acts quickly but evaporates fast.
, The chemical agent that produces highly toxic and reactive free radicals is
A. cidex.
B. cationic detergents.
C. hydrogen peroxide.
D. chlorhexidine.
E. iodophors.
✅ Correct answer: C. hydrogen peroxide
Rationale: Hydrogen peroxide decomposes to form oxygen free radicals that attack proteins,
DNA, and membranes.
Hydrogen peroxide can be
A. sporicidal.
B. fungicidal.
C. bactericidal.
D. virucidal.
E. All of the choices are correct.
✅ Correct answer: E. All of the choices are correct.
Rationale: Hydrogen peroxide has a broad spectrum, capable of destroying spores, fungi,
bacteria, and viruses at high concentrations.
All of the following disrupt the cytoplasmic membrane except
A. detergents.
B. quaternary ammonium compounds.
C. high concentration phenols.
D. iodine.
✅ Correct answer: D. iodine
Rationale: Iodine acts by halogenating proteins and enzymes, not directly by disrupting
membranes.
Heavy metals work by
A. rupturing the cell membrane.
B. inactivating proteins.
C. binding to DNA.
D. dissolving the cell wall.
E. mutating DNA.
✅ Correct answer: B. inactivating proteins
Rationale: Heavy metals like silver and mercury bind to functional groups in proteins, rendering
them inactive.
Quiz and Assessment Workbook
Filtration can result in sterilization of serum and blood products
A. by removing viruses.
B. by relying on gravity.
C. by removing toxins.
D. using high heat and filtration.
✅ Correct answer: A. by removing viruses
Rationale: Filtration works by physically removing microorganisms, including viruses, from
heat-sensitive solutions. It doesn’t rely on heat or remove toxins. Gravity alone is not sufficient
for sterilization.
_____ is a control method that removes microorganisms rather than inhibiting or killing
them.
A. Boiling
B. Sterilization
C. Radiation
D. Filtration
E. Disinfection
✅ Correct answer: D. Filtration
Rationale: Filtration removes microbes without killing or inhibiting them, unlike boiling,
disinfection, or sterilization which destroy microorganisms.
Which of the following is not a factor that affects germicidal activity?
A. the material being treated
B. the length of exposure
C. the strength of the germicide
D. the microorganism being treated
E. All of these are factors.
✅ Correct answer: E. All of these are factors.
Rationale: Each listed variable influences the effectiveness of a germicide; therefore, all are
relevant factors.
All of the following pertain to hypochlorites except
A. release hypochlorous acid in solution.
B. cause denaturation of enzymes.
,C. found in iodophors.
D. used to disinfect water, restaurant, and medical equipment.
E. found in common household bleach.
✅ Correct answer: C. found in iodophors.
Rationale: Iodophors contain iodine, not hypochlorite. Hypochlorites are chlorine compounds
used for disinfection and enzyme denaturation.
_____ is a halogen used in gaseous and liquid form for large-scale disinfection of drinking
water and sewage.
A. Iodine
B. Chlorine
C. Bromine
D. Fluorine
E. All of the choices are correct.
✅ Correct answer: B. Chlorine
Rationale: Chlorine is the main halogen used in water and sewage treatment due to its strong
oxidizing and germicidal properties.
The compound that is an organic base containing chlorine and two phenolic rings...
A. carbolic acid.
B. chlorhexidine.
C. triclosan.
D. formalin.
E. quaternary ammonium compounds.
✅ Correct answer: B. chlorhexidine
Rationale: Chlorhexidine is used for skin disinfection and mucous membrane cleaning; it
contains chlorinated aromatic rings and is broad-spectrum.
Alcohols
A. dissolve membrane lipids at concentrations greater than 50%.
B. can be used for disinfection or antisepsis.
C. are skin degerming agents.
D. are limited in effectiveness due to rapid evaporation.
E. All of the choices are correct.
✅ Correct answer: E. All of the choices are correct.
Rationale: All statements describe alcohol’s properties — it dissolves lipids, removes microbes
from skin, and acts quickly but evaporates fast.
, The chemical agent that produces highly toxic and reactive free radicals is
A. cidex.
B. cationic detergents.
C. hydrogen peroxide.
D. chlorhexidine.
E. iodophors.
✅ Correct answer: C. hydrogen peroxide
Rationale: Hydrogen peroxide decomposes to form oxygen free radicals that attack proteins,
DNA, and membranes.
Hydrogen peroxide can be
A. sporicidal.
B. fungicidal.
C. bactericidal.
D. virucidal.
E. All of the choices are correct.
✅ Correct answer: E. All of the choices are correct.
Rationale: Hydrogen peroxide has a broad spectrum, capable of destroying spores, fungi,
bacteria, and viruses at high concentrations.
All of the following disrupt the cytoplasmic membrane except
A. detergents.
B. quaternary ammonium compounds.
C. high concentration phenols.
D. iodine.
✅ Correct answer: D. iodine
Rationale: Iodine acts by halogenating proteins and enzymes, not directly by disrupting
membranes.
Heavy metals work by
A. rupturing the cell membrane.
B. inactivating proteins.
C. binding to DNA.
D. dissolving the cell wall.
E. mutating DNA.
✅ Correct answer: B. inactivating proteins
Rationale: Heavy metals like silver and mercury bind to functional groups in proteins, rendering
them inactive.
