BIO 250 Exam 4 V2 | BIO 250 Microbiology
| Actual Q&A with Rationale (BIO250 Exam
4) | StraighterLine
1. Which of the following are considered components of the second line of host defense?
(Select all that apply)
A. Fever
B. Inflammation
C. Phagocytosis
D. Interferon production
E. Intact skin
F. Ciliary escalator
Correct Answer: A, B, C, D
The second line of defense consists of internal, non-specific systems that activate once the
primary barriers are breached. This includes cellular processes such as phagocytosis and
physiological responses like fever and inflammation. Antimicrobial proteins like interferon
also play a crucial role in this stage of the innate immune response.
2. A pharmaceutical agent that inhibits the cross-linking of peptidoglycan subunits in the
bacterial cell wall belongs to which class?
A. Beta-lactams
,B. Aminoglycosides
C. Quinolones
D. Tetracyclines
Correct Answer: A
Beta-lactam antibiotics, including penicillin and cephalosporins, target the transpeptidase
enzymes responsible for cross-linking peptidoglycan. By preventing these links, the
bacterial cell wall becomes structurally weak and prone to osmotic lysis. This mechanism is
primarily bactericidal and most effective against actively growing cells.
3. Which immunoglobulin class is primarily responsible for the allergic response and binds to
mast cells and basophils?
A. IgG
B. IgE
C. IgA
D. IgM
E. IgD
Correct Answer: B
IgE is the antibody isotype associated with Type I hypersensitivity reactions and parasitic
infections. It binds to high-affinity receptors on mast cells, triggering the release of
,histamine upon allergen cross-linking. While it is the least abundant antibody in serum, its
physiological impact on allergic symptoms is significant.
4. Identify the process by which white blood cells migrate out of the mammalian blood
vessels and into the surrounding tissues to reach a site of infection.
A. Opsonization
B. Chemotaxis
C. Diapedesis
D. Phagocytosis
Correct Answer: C
Diapedesis, also known as extravasation, is the process where leukocytes change shape to
squeeze through the endothelial gaps in capillary walls. This movement is stimulated by
inflammatory mediators that increase vascular permeability. Once in the tissue, these cells
follow chemical signals to the exact location of the pathogen.
5. The Major Histocompatibility Complex (MHC) Class I molecules are found on which of the
following cell types?
A. Only on B cells and macrophages
B. Red blood cells and platelets
C. Only on T helper cells
D. All nucleated cells
, Correct Answer: D
MHC Class I molecules are expressed on almost all nucleated cells in the human body to
present endogenous antigens to CD8+ T cells. This system allows the immune system to
monitor the internal health of cells and identify those infected by viruses or becoming
cancerous. Red blood cells lack a nucleus and therefore do not express MHC I.
6. Which of the following are characteristics of the Adaptive (Specific) immune system?
(Select all that apply)
A. Memory
B. Specificity
C. Ability to distinguish self from non-self
D. Immediate response upon first exposure
E. Indiscriminate destruction of all microbes
Correct Answer: A, B, C
Adaptive immunity is characterized by its high degree of specificity toward individual
molecular shapes called epitopes. It also possesses a memory component that allows for a
much faster and more robust response upon subsequent exposures to the same pathogen.
Unlike innate immunity, it requires an activation period following the first encounter with
a new antigen.
| Actual Q&A with Rationale (BIO250 Exam
4) | StraighterLine
1. Which of the following are considered components of the second line of host defense?
(Select all that apply)
A. Fever
B. Inflammation
C. Phagocytosis
D. Interferon production
E. Intact skin
F. Ciliary escalator
Correct Answer: A, B, C, D
The second line of defense consists of internal, non-specific systems that activate once the
primary barriers are breached. This includes cellular processes such as phagocytosis and
physiological responses like fever and inflammation. Antimicrobial proteins like interferon
also play a crucial role in this stage of the innate immune response.
2. A pharmaceutical agent that inhibits the cross-linking of peptidoglycan subunits in the
bacterial cell wall belongs to which class?
A. Beta-lactams
,B. Aminoglycosides
C. Quinolones
D. Tetracyclines
Correct Answer: A
Beta-lactam antibiotics, including penicillin and cephalosporins, target the transpeptidase
enzymes responsible for cross-linking peptidoglycan. By preventing these links, the
bacterial cell wall becomes structurally weak and prone to osmotic lysis. This mechanism is
primarily bactericidal and most effective against actively growing cells.
3. Which immunoglobulin class is primarily responsible for the allergic response and binds to
mast cells and basophils?
A. IgG
B. IgE
C. IgA
D. IgM
E. IgD
Correct Answer: B
IgE is the antibody isotype associated with Type I hypersensitivity reactions and parasitic
infections. It binds to high-affinity receptors on mast cells, triggering the release of
,histamine upon allergen cross-linking. While it is the least abundant antibody in serum, its
physiological impact on allergic symptoms is significant.
4. Identify the process by which white blood cells migrate out of the mammalian blood
vessels and into the surrounding tissues to reach a site of infection.
A. Opsonization
B. Chemotaxis
C. Diapedesis
D. Phagocytosis
Correct Answer: C
Diapedesis, also known as extravasation, is the process where leukocytes change shape to
squeeze through the endothelial gaps in capillary walls. This movement is stimulated by
inflammatory mediators that increase vascular permeability. Once in the tissue, these cells
follow chemical signals to the exact location of the pathogen.
5. The Major Histocompatibility Complex (MHC) Class I molecules are found on which of the
following cell types?
A. Only on B cells and macrophages
B. Red blood cells and platelets
C. Only on T helper cells
D. All nucleated cells
, Correct Answer: D
MHC Class I molecules are expressed on almost all nucleated cells in the human body to
present endogenous antigens to CD8+ T cells. This system allows the immune system to
monitor the internal health of cells and identify those infected by viruses or becoming
cancerous. Red blood cells lack a nucleus and therefore do not express MHC I.
6. Which of the following are characteristics of the Adaptive (Specific) immune system?
(Select all that apply)
A. Memory
B. Specificity
C. Ability to distinguish self from non-self
D. Immediate response upon first exposure
E. Indiscriminate destruction of all microbes
Correct Answer: A, B, C
Adaptive immunity is characterized by its high degree of specificity toward individual
molecular shapes called epitopes. It also possesses a memory component that allows for a
much faster and more robust response upon subsequent exposures to the same pathogen.
Unlike innate immunity, it requires an activation period following the first encounter with
a new antigen.
