BIOS 242 EXAM 3 REVIEW –
FUNDAMENTALS OF MICROBIOLOGY |
200+ QUESTIONS WITH VERIFIED
ANSWERS & RATIONALES |
CHAMBERLAIN | GRADED A+
🛡️ Section 1: Immunology – The Three Lines of Defense
1. What are the three lines of defense in the immune system?
A) Physical barriers, inflammation, and antibodies
B) Innate immunity, adaptive immunity, and memory
C) First line (physical/chemical barriers), second line (innate immunity), third line
(adaptive immunity)
D) Skin, mucous membranes, and fever
Correct Answer: C
The three lines of defense are: 1st line (physical and chemical barriers like skin and
mucous membranes), 2nd line (innate immunity – phagocytes, inflammation, fever),
and 3rd line (adaptive immunity – specific immune responses with memory).
2. The first line of defense is a surface protection composed of _____ and _____
barriers that keep microbes from penetrating sterile body compartments.
A) Chemical; biological
B) Anatomical; physiological
C) Cellular; chemical
D) Physical; mechanical
Correct Answer: B
The first line of defense consists of anatomical (skin, mucous membranes) and
physiological (pH, temperature, antimicrobial chemicals) barriers that prevent
microbial entry.
3. Innate immunity is characterized by which of the following?
A) Specificity and memory
B) Non-specific response present from birth, without memory
C) Antibody-mediated response
D) Slow response to pathogens
,Correct Answer: B
Innate immunity is present at birth, responds immediately, and is non-specific. The
third line (adaptive immunity) develops after exposure to specific antigens.
4. Which of the following is considered a first-line defense mechanism?
A) Phagocytosis
B) Inflammation
C) Skin
D) Antibody production
Correct Answer: C
The first line of defense includes physical and chemical barriers that prevent pathogen
entry, such as skin, mucous membranes, and secretions like tears and saliva.
Phagocytosis and inflammation are second-line defenses.
5. The second line of defense is a _____ and _____ system that comes into play if
infectious agents make it past the surface defenses.
A) Cellular; chemical
B) Anatomical; physiological
C) Physical; mechanical
D) Adaptive; specific
Correct Answer: A
The second line of defense includes cellular components (phagocytes, natural killer
cells) and chemical components (interferons, complement proteins, inflammatory
mediators).
6. Where do B cells mature?
Correct Answer: Red bone marrow
B cells develop and mature in the red bone marrow, where they also undergo selection
processes to prevent autoimmunity.
7. Where do T cells mature?
Correct Answer: Thymus
T cells develop in the bone marrow and mature in the thymus, where they undergo
positive and negative selection.
8. What are the physical barriers on the skin?
Correct Answer: Hair follicles, sweat glands, mucous membranes
The skin's physical barriers include the epidermis itself, hair follicles, sweat glands, and
mucous membranes that line body cavities open to the environment.
9. What are the chemical barriers of the skin?
Correct Answer: Lysozyme, saliva, sweat, skin's pH, hydrochloric acid, bile,
resident microbiota
,Chemical barriers include antimicrobial substances like lysozyme (in tears and saliva),
the acidic pH of the skin and stomach (hydrochloric acid), bile in the intestines, and
competition from resident microbiota.
10. Which of the following is a protective cell of the second line of defense?
A) B lymphocyte
B) T lymphocyte
C) Macrophage
D) Antibody
Correct Answer: C
Macrophages are phagocytic cells that are part of the second line of defense (innate
immunity). B and T lymphocytes are part of the third line of defense (adaptive
immunity).
🦠 Section 2: Microbial Pathogenesis & Virulence Factors
1. A Gram-negative bacillus isolated from a wound is oxidase-positive, grows at
42°C, and produces a blue-green pigment. Which virulence factor most directly
explains its ability to form biofilms on catheters?
A) Type III secretion system injecting effector proteins
B) Alginate exopolysaccharide production
C) Endotoxin-mediated septic shock
D) Exotoxin A inhibiting EF-2
Correct Answer: B
Pseudomonas aeruginosa produces alginate, a mucoid exopolysaccharide that encases
biofilm communities and confers resistance to phagocytosis and antibiotics. Type III
secretion and exotoxin A are virulence mechanisms but do not directly mediate biofilm
matrix formation; endotoxin triggers inflammation but is not a biofilm structural
component.
2. A patient develops severe diarrhea after broad-spectrum antibiotics. Stool
testing reveals a toxigenic strain with a pathogenicity island encoding toxins A
and B. Which mechanism best explains the intestinal damage?
A) Toxin B glucosylates Rho GTPases, disrupting actin cytoskeleton
B) Toxin A activates adenylate cyclase, increasing cAMP
C) Toxin B inhibits protein synthesis via EF-2 ribosylation
D) Toxin A forms pores in the cell membrane causing lysis
, Correct Answer: A
Clostridium difficile toxins A and B are glucosyltransferases that inactivate Rho-family
GTPases, leading to cytoskeletal disruption, tight junction loss, and colitis. cAMP
elevation is characteristic of cholera toxin; EF-2 ribosylation is diphtheria/Pseudomonas
exotoxin; pore formation is seen with other toxins like alpha-toxin.
3. During a norovirus outbreak on a cruise ship, which combination of
properties most accounts for the virus's extreme environmental stability and
resistance to alcohol-based sanitizers?
A) Enveloped, RNA genome, low infectious dose
B) Non-enveloped, RNA genome, low infectious dose
C) Enveloped, DNA genome, high infectious dose
D) Non-enveloped, DNA genome, high infectious dose
Correct Answer: B
Norovirus is a non-enveloped, positive-sense RNA virus with a very low infectious dose
(as few as 18 virions), making it highly stable and resistant to alcohol. Enveloped
viruses are generally more susceptible to disinfectants; DNA genome and high
infectious dose are incorrect for norovirus.
4. A nurse must choose a disinfectant for a flexible endoscope that will contact
mucous membranes. Which property is most critical to ensure high-level
disinfection while avoiding patient injury?
A) High alcohol concentration for rapid evaporation
B) Ability to kill bacterial spores within 10 minutes
C) Material compatibility and complete rinsing to remove toxic residues
D) Strong oxidizing agent that degrades organic matter
Correct Answer: C
For a flexible endoscope contacting mucous membranes, high-level disinfection is
required. The most critical property is material compatibility (to avoid damaging the
instrument) and complete rinsing to remove toxic residues that could injure the patient.
Sporicidal activity may be required for certain situations, but patient safety through
rinsing is paramount.
🧬 Section 3: Microbial Genetics & Antimicrobial Drugs
1. Which of the following best describes the process of translation?
A) DNA is copied to form mRNA
B) mRNA is decoded to build a protein
FUNDAMENTALS OF MICROBIOLOGY |
200+ QUESTIONS WITH VERIFIED
ANSWERS & RATIONALES |
CHAMBERLAIN | GRADED A+
🛡️ Section 1: Immunology – The Three Lines of Defense
1. What are the three lines of defense in the immune system?
A) Physical barriers, inflammation, and antibodies
B) Innate immunity, adaptive immunity, and memory
C) First line (physical/chemical barriers), second line (innate immunity), third line
(adaptive immunity)
D) Skin, mucous membranes, and fever
Correct Answer: C
The three lines of defense are: 1st line (physical and chemical barriers like skin and
mucous membranes), 2nd line (innate immunity – phagocytes, inflammation, fever),
and 3rd line (adaptive immunity – specific immune responses with memory).
2. The first line of defense is a surface protection composed of _____ and _____
barriers that keep microbes from penetrating sterile body compartments.
A) Chemical; biological
B) Anatomical; physiological
C) Cellular; chemical
D) Physical; mechanical
Correct Answer: B
The first line of defense consists of anatomical (skin, mucous membranes) and
physiological (pH, temperature, antimicrobial chemicals) barriers that prevent
microbial entry.
3. Innate immunity is characterized by which of the following?
A) Specificity and memory
B) Non-specific response present from birth, without memory
C) Antibody-mediated response
D) Slow response to pathogens
,Correct Answer: B
Innate immunity is present at birth, responds immediately, and is non-specific. The
third line (adaptive immunity) develops after exposure to specific antigens.
4. Which of the following is considered a first-line defense mechanism?
A) Phagocytosis
B) Inflammation
C) Skin
D) Antibody production
Correct Answer: C
The first line of defense includes physical and chemical barriers that prevent pathogen
entry, such as skin, mucous membranes, and secretions like tears and saliva.
Phagocytosis and inflammation are second-line defenses.
5. The second line of defense is a _____ and _____ system that comes into play if
infectious agents make it past the surface defenses.
A) Cellular; chemical
B) Anatomical; physiological
C) Physical; mechanical
D) Adaptive; specific
Correct Answer: A
The second line of defense includes cellular components (phagocytes, natural killer
cells) and chemical components (interferons, complement proteins, inflammatory
mediators).
6. Where do B cells mature?
Correct Answer: Red bone marrow
B cells develop and mature in the red bone marrow, where they also undergo selection
processes to prevent autoimmunity.
7. Where do T cells mature?
Correct Answer: Thymus
T cells develop in the bone marrow and mature in the thymus, where they undergo
positive and negative selection.
8. What are the physical barriers on the skin?
Correct Answer: Hair follicles, sweat glands, mucous membranes
The skin's physical barriers include the epidermis itself, hair follicles, sweat glands, and
mucous membranes that line body cavities open to the environment.
9. What are the chemical barriers of the skin?
Correct Answer: Lysozyme, saliva, sweat, skin's pH, hydrochloric acid, bile,
resident microbiota
,Chemical barriers include antimicrobial substances like lysozyme (in tears and saliva),
the acidic pH of the skin and stomach (hydrochloric acid), bile in the intestines, and
competition from resident microbiota.
10. Which of the following is a protective cell of the second line of defense?
A) B lymphocyte
B) T lymphocyte
C) Macrophage
D) Antibody
Correct Answer: C
Macrophages are phagocytic cells that are part of the second line of defense (innate
immunity). B and T lymphocytes are part of the third line of defense (adaptive
immunity).
🦠 Section 2: Microbial Pathogenesis & Virulence Factors
1. A Gram-negative bacillus isolated from a wound is oxidase-positive, grows at
42°C, and produces a blue-green pigment. Which virulence factor most directly
explains its ability to form biofilms on catheters?
A) Type III secretion system injecting effector proteins
B) Alginate exopolysaccharide production
C) Endotoxin-mediated septic shock
D) Exotoxin A inhibiting EF-2
Correct Answer: B
Pseudomonas aeruginosa produces alginate, a mucoid exopolysaccharide that encases
biofilm communities and confers resistance to phagocytosis and antibiotics. Type III
secretion and exotoxin A are virulence mechanisms but do not directly mediate biofilm
matrix formation; endotoxin triggers inflammation but is not a biofilm structural
component.
2. A patient develops severe diarrhea after broad-spectrum antibiotics. Stool
testing reveals a toxigenic strain with a pathogenicity island encoding toxins A
and B. Which mechanism best explains the intestinal damage?
A) Toxin B glucosylates Rho GTPases, disrupting actin cytoskeleton
B) Toxin A activates adenylate cyclase, increasing cAMP
C) Toxin B inhibits protein synthesis via EF-2 ribosylation
D) Toxin A forms pores in the cell membrane causing lysis
, Correct Answer: A
Clostridium difficile toxins A and B are glucosyltransferases that inactivate Rho-family
GTPases, leading to cytoskeletal disruption, tight junction loss, and colitis. cAMP
elevation is characteristic of cholera toxin; EF-2 ribosylation is diphtheria/Pseudomonas
exotoxin; pore formation is seen with other toxins like alpha-toxin.
3. During a norovirus outbreak on a cruise ship, which combination of
properties most accounts for the virus's extreme environmental stability and
resistance to alcohol-based sanitizers?
A) Enveloped, RNA genome, low infectious dose
B) Non-enveloped, RNA genome, low infectious dose
C) Enveloped, DNA genome, high infectious dose
D) Non-enveloped, DNA genome, high infectious dose
Correct Answer: B
Norovirus is a non-enveloped, positive-sense RNA virus with a very low infectious dose
(as few as 18 virions), making it highly stable and resistant to alcohol. Enveloped
viruses are generally more susceptible to disinfectants; DNA genome and high
infectious dose are incorrect for norovirus.
4. A nurse must choose a disinfectant for a flexible endoscope that will contact
mucous membranes. Which property is most critical to ensure high-level
disinfection while avoiding patient injury?
A) High alcohol concentration for rapid evaporation
B) Ability to kill bacterial spores within 10 minutes
C) Material compatibility and complete rinsing to remove toxic residues
D) Strong oxidizing agent that degrades organic matter
Correct Answer: C
For a flexible endoscope contacting mucous membranes, high-level disinfection is
required. The most critical property is material compatibility (to avoid damaging the
instrument) and complete rinsing to remove toxic residues that could injure the patient.
Sporicidal activity may be required for certain situations, but patient safety through
rinsing is paramount.
🧬 Section 3: Microbial Genetics & Antimicrobial Drugs
1. Which of the following best describes the process of translation?
A) DNA is copied to form mRNA
B) mRNA is decoded to build a protein
