Page 1 of 73
BIO 290 EXAM WITH VERIFIED ANSWERS DETAILED
RATIONALES GRADED A+
BIO 290 EXAM
SECTION 1: INNATE IMMUNITY & FIRST LINES OF DEFENSE (Questions 1–25)
1. Which of the following is considered the body's first line of defense against invading
pathogens?
A. Inflammation
B. Fever
C. Intact skin and mucous membranes
D. Phagocytosis
Rationale: The first line of defense consists of physical and chemical barriers, including intact
skin, mucous membranes, and secretions, which prevent pathogen entry. Inflammation, fever,
and phagocytosis are second-line defenses.
2. Which of the following best describes the role of lysozyme in innate immunity?
A. It lyses bacterial cell walls by breaking down peptidoglycan
B. It enhances phagocytosis by coating pathogens
C. It triggers the complement cascade
D. It produces antibodies against pathogens
Rationale: Lysozyme is an enzyme found in tears, saliva, and mucus that hydrolyzes the bond
between NAG and NAM in peptidoglycan, causing bacterial cell lysis.
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3. Which of the following complement pathways is activated by antibodies bound to
antigens?
A. Alternative pathway
B. Classical pathway
C. Lectin pathway
D. Coagulation pathway
Rationale: The classical complement pathway is triggered when antibodies (IgG or IgM) bind to
antigens, forming antigen-antibody complexes that activate C1.
4. What is the primary function of defensins in innate immunity?
A. They form pores in microbial membranes, causing cell lysis
B. They neutralize viruses
C. They promote blood clotting
D. They produce antibodies
Rationale: Defensins are antimicrobial peptides that insert into microbial membranes, forming
pores that disrupt membrane integrity and cause cell death.
5. Which of the following is a characteristic sign of inflammation?
A. Vasoconstriction
B. Decreased blood flow
C. Redness, heat, swelling, and pain
D. Reduced vascular permeability
Rationale: Inflammation is characterized by redness, heat, swelling, pain, and sometimes loss of
function. These signs result from vasodilation and increased vascular permeability.
6. What is the primary purpose of fever in the innate immune response?
A. To increase body temperature to inhibit pathogen growth and enhance immune activity
B. To reduce blood flow to infected tissues
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C. To promote antibody production
D. To cause vasoconstriction
Rationale: Fever raises body temperature, which inhibits the growth of temperature-sensitive
pathogens and enhances phagocytic activity and immune responses.
7. Which of the following cells are the primary phagocytes in the innate immune system?
A. B-lymphocytes and T-lymphocytes
B. Neutrophils and macrophages
C. Basophils and eosinophils
D. Plasma cells and memory cells
Rationale: Neutrophils and macrophages are the primary phagocytic cells of the innate immune
system, responsible for engulfing and destroying pathogens.
8. What is the role of opsonins in the immune response?
A. They coat pathogens to enhance phagocytosis
B. They directly lyse pathogens
C. They produce antibodies
D. They suppress immune responses
Rationale: Opsonins (e.g., antibodies, complement proteins) coat pathogens, making them
more recognizable and easier for phagocytes to engulf.
9. Which of the following is a chemical barrier of the first line of defense?
A. Skin
B. Mucous membranes
C. Lysozyme in tears
D. Fever
Rationale: Lysozyme in tears is a chemical barrier that destroys bacteria. Skin and mucous
membranes are physical barriers, while fever is a second-line defense.
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10. Which pattern recognition receptors recognize pathogen-associated molecular patterns
(PAMPs)?
A. Toll-like receptors (TLRs)
B. Immunoglobulins
C. Major histocompatibility complex (MHC)
D. Complement receptors
Rationale: Toll-like receptors (TLRs) recognize PAMPs, such as lipopolysaccharide and
peptidoglycan, initiating innate immune responses.
11. What is the primary function of natural killer (NK) cells?
A. To kill virus-infected cells and tumor cells
B. To produce antibodies
C. To activate complement
D. To present antigens to T-cells
Rationale: NK cells are innate lymphoid cells that kill virus-infected cells and tumor cells without
prior sensitization, using perforin and granzymes.
12. Which of the following is a characteristic of the alternative complement pathway?
A. It is activated by antibodies
B. It is activated by microbial surface molecules
C. It is activated by mannose-binding lectin
D. It requires C1
Rationale: The alternative complement pathway is activated by microbial surface molecules
(e.g., LPS) in the absence of antibodies, providing rapid innate defense.
13. What is the role of interferons in innate immunity?
A. They interfere with viral replication in infected cells
B. They promote inflammation
4|Page
BIO 290 EXAM WITH VERIFIED ANSWERS DETAILED
RATIONALES GRADED A+
BIO 290 EXAM
SECTION 1: INNATE IMMUNITY & FIRST LINES OF DEFENSE (Questions 1–25)
1. Which of the following is considered the body's first line of defense against invading
pathogens?
A. Inflammation
B. Fever
C. Intact skin and mucous membranes
D. Phagocytosis
Rationale: The first line of defense consists of physical and chemical barriers, including intact
skin, mucous membranes, and secretions, which prevent pathogen entry. Inflammation, fever,
and phagocytosis are second-line defenses.
2. Which of the following best describes the role of lysozyme in innate immunity?
A. It lyses bacterial cell walls by breaking down peptidoglycan
B. It enhances phagocytosis by coating pathogens
C. It triggers the complement cascade
D. It produces antibodies against pathogens
Rationale: Lysozyme is an enzyme found in tears, saliva, and mucus that hydrolyzes the bond
between NAG and NAM in peptidoglycan, causing bacterial cell lysis.
1|Page
,Page 2 of 73
3. Which of the following complement pathways is activated by antibodies bound to
antigens?
A. Alternative pathway
B. Classical pathway
C. Lectin pathway
D. Coagulation pathway
Rationale: The classical complement pathway is triggered when antibodies (IgG or IgM) bind to
antigens, forming antigen-antibody complexes that activate C1.
4. What is the primary function of defensins in innate immunity?
A. They form pores in microbial membranes, causing cell lysis
B. They neutralize viruses
C. They promote blood clotting
D. They produce antibodies
Rationale: Defensins are antimicrobial peptides that insert into microbial membranes, forming
pores that disrupt membrane integrity and cause cell death.
5. Which of the following is a characteristic sign of inflammation?
A. Vasoconstriction
B. Decreased blood flow
C. Redness, heat, swelling, and pain
D. Reduced vascular permeability
Rationale: Inflammation is characterized by redness, heat, swelling, pain, and sometimes loss of
function. These signs result from vasodilation and increased vascular permeability.
6. What is the primary purpose of fever in the innate immune response?
A. To increase body temperature to inhibit pathogen growth and enhance immune activity
B. To reduce blood flow to infected tissues
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,Page 3 of 73
C. To promote antibody production
D. To cause vasoconstriction
Rationale: Fever raises body temperature, which inhibits the growth of temperature-sensitive
pathogens and enhances phagocytic activity and immune responses.
7. Which of the following cells are the primary phagocytes in the innate immune system?
A. B-lymphocytes and T-lymphocytes
B. Neutrophils and macrophages
C. Basophils and eosinophils
D. Plasma cells and memory cells
Rationale: Neutrophils and macrophages are the primary phagocytic cells of the innate immune
system, responsible for engulfing and destroying pathogens.
8. What is the role of opsonins in the immune response?
A. They coat pathogens to enhance phagocytosis
B. They directly lyse pathogens
C. They produce antibodies
D. They suppress immune responses
Rationale: Opsonins (e.g., antibodies, complement proteins) coat pathogens, making them
more recognizable and easier for phagocytes to engulf.
9. Which of the following is a chemical barrier of the first line of defense?
A. Skin
B. Mucous membranes
C. Lysozyme in tears
D. Fever
Rationale: Lysozyme in tears is a chemical barrier that destroys bacteria. Skin and mucous
membranes are physical barriers, while fever is a second-line defense.
3|Page
, Page 4 of 73
10. Which pattern recognition receptors recognize pathogen-associated molecular patterns
(PAMPs)?
A. Toll-like receptors (TLRs)
B. Immunoglobulins
C. Major histocompatibility complex (MHC)
D. Complement receptors
Rationale: Toll-like receptors (TLRs) recognize PAMPs, such as lipopolysaccharide and
peptidoglycan, initiating innate immune responses.
11. What is the primary function of natural killer (NK) cells?
A. To kill virus-infected cells and tumor cells
B. To produce antibodies
C. To activate complement
D. To present antigens to T-cells
Rationale: NK cells are innate lymphoid cells that kill virus-infected cells and tumor cells without
prior sensitization, using perforin and granzymes.
12. Which of the following is a characteristic of the alternative complement pathway?
A. It is activated by antibodies
B. It is activated by microbial surface molecules
C. It is activated by mannose-binding lectin
D. It requires C1
Rationale: The alternative complement pathway is activated by microbial surface molecules
(e.g., LPS) in the absence of antibodies, providing rapid innate defense.
13. What is the role of interferons in innate immunity?
A. They interfere with viral replication in infected cells
B. They promote inflammation
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