BIOD 171 | BIOD 171 Microbiology Module 8 Exam
| Questions with Correct Answers and Expert
Explanation for Each Question | Portage Learning
1. Which of the following is considered a primary component of the first line of
defense in the innate immune system?
A. T-lymphocytes
B. Physical barriers like skin and mucous membranes
C. Antibody production
D. Memory B cells
Correct Answer: B
Expert Explanation: The first line of defense is composed of physical and chemical
barriers that prevent pathogen entry. Skin provides a tough waterproof layer while
mucous membranes trap microbes in various body tracts. These mechanisms are
non-specific and act immediately upon exposure to any foreign agent. Unlike the
adaptive system, this barrier does not require prior sensitization to function
effectively. Therefore, maintaining the integrity of these barriers is crucial for
preventing initial infections.
2. What is the primary role of neutrophils during an acute inflammatory response?
A. Production of high-affinity IgG antibodies
,B. Phagocytosis of invading pathogens
C. Presentation of antigens to Helper T cells
D. Release of histamine for allergic reactions
Correct Answer: B
Expert Explanation: Neutrophils are the most abundant type of white blood cell
and usually the first to arrive at a site of infection. Their main function is to seek out,
engulf, and destroy bacteria through the process of phagocytosis. They utilize
various enzymes and reactive oxygen species within their granules to kill
internalized microbes. This rapid response is a hallmark of the innate immune
system’s effort to contain localized threats. Once their task is finished, these cells
often undergo apoptosis and contribute to pus formation.
3. Which class of antibody is the first to be produced during a primary immune
response?
A. IgM
B. IgE
C. IgA
D. IgG
Correct Answer: A
,Expert Explanation: IgM is the first immunoglobulin class secreted by plasma cells
following the initial exposure to an antigen. It typically exists as a pentamer,
meaning it has ten binding sites for antigens to increase its effectiveness. Because of
its large size, it is highly efficient at agglutinating pathogens and activating the
complement system. Although its affinity for antigens is initially lower than IgG, its
high avidity compensates for this during early infection. Its presence in a patient’s
serum usually indicates a current or very recent infection.
4. Which process describes the coating of a pathogen with antibodies or complement
proteins to enhance phagocytosis?
A. Neutralization
B. Opsonization
C. Agglutination
D. Apoptosis
Correct Answer: B
Expert Explanation: Opsonization acts as a biological tagging system that makes
pathogens more ‘tasty’ or visible to phagocytes. Antibodies like IgG or complement
proteins like C3b bind to the surface of the microbe. Phagocytic cells such as
macrophages have specific receptors that recognize these opsonins, allowing for a
firmer grip. This significantly increases the speed and efficiency with which the
, pathogen is engulfed. Without opsonization, some encapsulated bacteria can evade
the immune system much more easily.
5. Which type of immunity is acquired when a mother passes antibodies to her fetus
through the placenta?
A. Naturally acquired active immunity
B. Artificially acquired active immunity
C. Naturally acquired passive immunity
D. Artificially acquired passive immunity
Correct Answer: C
Expert Explanation: Naturally acquired passive immunity involves the transfer of
pre-formed antibodies from one individual to another through natural means. In
this specific case, IgG antibodies cross the placental barrier to protect the
developing fetus. This provides the newborn with immediate protection against
pathogens the mother has encountered. However, this type of immunity is
temporary because the infant’s body is not producing the antibodies itself.
Eventually, these maternal antibodies degrade, and the child must develop its own
active immune response.
6. What is the function of Major Histocompatibility Complex (MHC) Class I molecules?
A. To present extracellular antigens to Helper T cells
| Questions with Correct Answers and Expert
Explanation for Each Question | Portage Learning
1. Which of the following is considered a primary component of the first line of
defense in the innate immune system?
A. T-lymphocytes
B. Physical barriers like skin and mucous membranes
C. Antibody production
D. Memory B cells
Correct Answer: B
Expert Explanation: The first line of defense is composed of physical and chemical
barriers that prevent pathogen entry. Skin provides a tough waterproof layer while
mucous membranes trap microbes in various body tracts. These mechanisms are
non-specific and act immediately upon exposure to any foreign agent. Unlike the
adaptive system, this barrier does not require prior sensitization to function
effectively. Therefore, maintaining the integrity of these barriers is crucial for
preventing initial infections.
2. What is the primary role of neutrophils during an acute inflammatory response?
A. Production of high-affinity IgG antibodies
,B. Phagocytosis of invading pathogens
C. Presentation of antigens to Helper T cells
D. Release of histamine for allergic reactions
Correct Answer: B
Expert Explanation: Neutrophils are the most abundant type of white blood cell
and usually the first to arrive at a site of infection. Their main function is to seek out,
engulf, and destroy bacteria through the process of phagocytosis. They utilize
various enzymes and reactive oxygen species within their granules to kill
internalized microbes. This rapid response is a hallmark of the innate immune
system’s effort to contain localized threats. Once their task is finished, these cells
often undergo apoptosis and contribute to pus formation.
3. Which class of antibody is the first to be produced during a primary immune
response?
A. IgM
B. IgE
C. IgA
D. IgG
Correct Answer: A
,Expert Explanation: IgM is the first immunoglobulin class secreted by plasma cells
following the initial exposure to an antigen. It typically exists as a pentamer,
meaning it has ten binding sites for antigens to increase its effectiveness. Because of
its large size, it is highly efficient at agglutinating pathogens and activating the
complement system. Although its affinity for antigens is initially lower than IgG, its
high avidity compensates for this during early infection. Its presence in a patient’s
serum usually indicates a current or very recent infection.
4. Which process describes the coating of a pathogen with antibodies or complement
proteins to enhance phagocytosis?
A. Neutralization
B. Opsonization
C. Agglutination
D. Apoptosis
Correct Answer: B
Expert Explanation: Opsonization acts as a biological tagging system that makes
pathogens more ‘tasty’ or visible to phagocytes. Antibodies like IgG or complement
proteins like C3b bind to the surface of the microbe. Phagocytic cells such as
macrophages have specific receptors that recognize these opsonins, allowing for a
firmer grip. This significantly increases the speed and efficiency with which the
, pathogen is engulfed. Without opsonization, some encapsulated bacteria can evade
the immune system much more easily.
5. Which type of immunity is acquired when a mother passes antibodies to her fetus
through the placenta?
A. Naturally acquired active immunity
B. Artificially acquired active immunity
C. Naturally acquired passive immunity
D. Artificially acquired passive immunity
Correct Answer: C
Expert Explanation: Naturally acquired passive immunity involves the transfer of
pre-formed antibodies from one individual to another through natural means. In
this specific case, IgG antibodies cross the placental barrier to protect the
developing fetus. This provides the newborn with immediate protection against
pathogens the mother has encountered. However, this type of immunity is
temporary because the infant’s body is not producing the antibodies itself.
Eventually, these maternal antibodies degrade, and the child must develop its own
active immune response.
6. What is the function of Major Histocompatibility Complex (MHC) Class I molecules?
A. To present extracellular antigens to Helper T cells
