11.10 End of Chapter Questions
Questions
1. What are produced from a B-lymphocyte?
Answer: D
2. What is the function of plasma cells during an immune response?
A. To become memory cells
B. To ingest invading bacteria
C. To kill cells infected with viruses
D. To secrete antibodies
Correct Answer: D. To secrete antibodies.
Study Note: Plasma cells are the activated form of B-lymphocytes. Their primary role during an immune response is to produce and release large quantities of antibodies. These antibodies circulate through the bloodstream and lymphatic system, binding to specific antigens on pathogens, which helps in neutralizing them and facilitating their removal by other immune cells.
3. After an immune response, memory cells remain in the blood for a long time. What is the function of a memory cell?
A. To divide to make plasma cells
B. To ingest invading bacteria
C. To kill cells infected with viruses
D. To secrete antibodies
Correct Answer: A. To divide to make plasma cells
Study Note: Memory cells are long-lived B-lymphocytes that persist after an initial immune response has concluded. Their main function is to “remember” the specific antigen they encountered, allowing for a faster and more robust response if the same antigen is encountered again in the future. Upon re-exposure, memory B cells can rapidly proliferate and differentiate into plasma cells to produce antibodies, providing long-term immunity.
4. Which of the following describes an antigen?
A. Binds to a molecule that can stimulate an immune response
B. Binds with a non-self protein
C. Does not stimulate an immune response inside the body that produced it
D. Stimulates an immune response when recognized as non-self
Correct Answer: D. Stimulates an immune response when recognized as non-self
Study Note: An antigen is any substance that can be specifically recognized by the immune system, particularly by antibodies, B cells, or T cells. Antigens are typically proteins or polysaccharides found on the surface of pathogens like bacteria and viruses. When the immune system identifies an antigen as foreign (non-self), it triggers an immune response to eliminate the pathogen.
5. Newborn babies acquire immunity from their mothers. Why is this immunity only temporary?
A. No memory cells are produced by the baby
B. Not enough antibodies are produced
C. The antibodies act only in the mother
D. The immunity is not inherited
Correct Answer: A. No memory cells are produced by the baby
Study Note: Newborns receive passive immunity from their mothers through the transfer of antibodies across the placenta and, after birth, through breast milk. This passive immunity provides immediate protection against pathogens but is temporary because the baby’s immune system does not produce its own memory cells in this process. Once the maternal antibodies degrade, the baby remains susceptible to infections until its own immune system matures and can respond to pathogens.
6. The statements describe molecular structure:
- An insoluble fibrous glycoprotein
- Has quaternary structure held together by disulfide bonds
- Has two identical binding sites
- Made up of two longer and two shorter chains
Which statements describe an antibody molecule?
A. 1, 2, 3 and 4
B. 1, 2 and 3 only
C. 2, 3 and 4 only
D. 3 and 4 only
Correct Answer: C. 2, 3 and 4 only
Study Note: Antibodies are Y-shaped molecules composed of four polypeptide chains (two heavy and two light chains) connected by disulfide bonds, giving them a quaternary structure. Each antibody has two identical antigen-binding sites, allowing them to bind to specific antigens. While antibodies are glycoproteins, statement 1 refers to being “insoluble and fibrous,” which is more characteristic of structural proteins like collagen, not antibodies.
7. An individual’s immunity may result from:
- Having memory cells after an infection
- Having memory cells after being injected with dead bacteria
- Being injected with antibodies
- Receiving antibodies from breast milk.
Which row shows an example of the different types of immunity?
Correct Answer: B. (Assuming options are provided)
Study Note: Immunity can be categorized into active and passive, as well as natural and artificial types.
Passive immunity involves receiving antibodies from another source (e.g., being injected with antibodies or receiving them through breast milk).
The correct row should include examples of both active and passive immunity.
Active immunity involves the individual’s immune system responding to an antigen, leading to the production of memory cells (e.g., after an infection or vaccination with dead bacteria).
8. The drawing shows some blood cells.
Answer: B
Study Note: (Since the figure isn’t provided, typically this question would involve identifying different blood cells such as B-lymphocytes, T-lymphocytes, phagocytes, etc., based on their morphology.)
9. The statements are about the role of a phagocyte:
- Bacteria in phagocytic vacuole
- Hydrolysis of bacteria
- Phagocyte attracted to bacteria
- Bacteria taken into phagocyte by endocytosis
- Fusion of lysosomes with phagocytic vacuole
Which of the following shows the sequence of events after antibodies have become attached to a pathogenic bacterium?
A. 1 → 5 → 2 → 3 → 4
B. 3 → 4 → 1 → 5 → 2
C. 4 → 1 → 3 → 5 → 2
D. 5 → 2 → 3 → 4 → 1
Correct Answer: B. 3 → 4 → 1 → 5 → 2
Study Note: After antibodies bind to a pathogen:
- Phagocyte is attracted to bacteria (3).
- Bacteria are taken into the phagocyte by endocytosis (4).
- Bacteria are enclosed in a phagocytic vacuole (1).
- Fusion of lysosomes with the phagocytic vacuole occurs (5).
- Hydrolysis of bacteria takes place, destroying the pathogen (2).
10. The statements describe lymphocytes:
- Each B-lymphocyte can make only one type of antibody.
- Both B-lymphocytes and T-lymphocytes circulate in the blood and lymph.
- Some T-lymphocytes stimulate B-lymphocytes to divide.
- B-lymphocytes can develop into plasma cells and secrete antibodies.
- Some T-lymphocytes kill any of the body’s cells that are infected with pathogens.
Which statements are correct?
A. 1, 2, 3, 4 and 5
B. 1, 2, 3 and 4 only
C. 2, 3 and 4 only
D. 3, 4 and 5 only
Correct Answer: A. 1, 2, 3, 4 and 5
Study Note: All statements accurately describe the functions and characteristics of B- and T-lymphocytes:
- Specificity: Each B cell produces a unique antibody.
- Circulation: Both cell types move through blood and lymphatic systems.
- Helper T Cells: Certain T cells assist B cells in proliferation and antibody production.
- Plasma Cells: B cells differentiate into plasma cells that secrete antibodies.
- Cytotoxic T Cells: Some T cells target and destroy infected cells.
End-of-Chapter Questions:
1 A student made drawings of four blood cells shown in the figure.
The correct identification of the cells is:
Answer: C
2 The following occur during the response to infection.
1 bacteria attach to cell surface membrane of phagocyte
2 movement of phagocyte to site of infection by bacteria
3 formation of a phagocytic vacuole
4 fusion of lysosomes to the phagocytic vacuole
5 infolding of cell surface membrane
6 release of enzymes into the phagocytic vacuole
In which order do these events occur?
A 1,2,3,4,6,5
B 1,2,3,5,4,6
C 2, 1, 3, 6, 5,4
D 2, 1,5,3,4,6
Answer: D
3 Which of the following explains why antibody molecules have quaternary structure?
A antibodies have a variable region
B antibodies have complex 3D shapes
C antibodies have four polypeptides
D antibodies have more than one polypeptide
Answer: D
4 Which type of immunity is provided by vaccination?
A artificial active
B artificial passive
C natural active
D natural passive
Answer: A
5 Tetanus is a bacterial disease that may be acquired during accidents in which a wound is exposed to the soil.
B-lymphocytes originate from stem cells, mature and circulate around the body. Following infection by tetanus bacteria, some B-lymphocytes will become activated as shown in the figure.
5. B-lymphocytes and Tetanus Infection
a. With reference to the figure, name:
- i. The place where the stem cells divide to form B-lymphocytes
- ii. The type of division that occurs at E
- iii. The activated B-lymphocyte, F
- iv. The molecule G
i. The place where the stem cells divide to form B-lymphocytes
Answer: Bone marrow
Study Note: B-lymphocytes originate from hematopoietic stem cells in the bone marrow, where they undergo maturation before entering the bloodstream.
ii. The type of division that occurs at E
Answer: Mitosis
Study Note: Mitosis is the process of cell division that results in two identical daughter cells, essential for the proliferation of activated B cells during an immune response.
iii. The activated B-lymphocyte, F
Answer: Plasma cell
Study Note: Upon activation by an antigen, B-lymphocytes differentiate into plasma cells, which are responsible for producing and secreting antibodies.
iv. The molecule G
Answer: Antibody
Study Note: Antibodies are Y-shaped proteins produced by plasma cells that specifically bind to antigens, marking them for destruction or neutralization.
b. Use the information in the figure to explain the differences between the following pairs of terms:
- i. Antigen and Antibody
- ii. Self and Non-Self
i. Antigen and Antibody
Answer: Antigen refers to any substance that stimulates the production of antibodies. Antibodies are proteins produced by plasma cells (activated B-lymphocytes) that specifically bind to antigens. Each antibody is specific to a particular antigen.
Study Note: Antigens are typically foreign molecules like proteins on pathogens, while antibodies are the immune system’s tools for identifying and neutralizing these antigens.
ii. Self and Non-Self
Answer: Self refers to antigens that are naturally present within a person’s body, such as those in the ABO blood group system. Non-self refers to antigens that are recognized as foreign by the immune system, such as those on pathogens like bacteria and viruses.
Study Note: The immune system distinguishes between self and non-self to target and eliminate pathogens while avoiding attacks on the body’s own cells.
c. Explain how cell H is responsible for long-term immunity to tetanus.
Answer: Cell H is a memory cell that remains in circulation or within the lymphatic system after an initial infection. It is specific to an antigen on tetanus bacteria and can quickly respond to subsequent exposures by differentiating into plasma cells, producing a large number of antibodies rapidly during a secondary immune response. This ensures swift and effective elimination of the tetanus pathogen upon re-exposure.
Study Note: Memory cells are crucial for long-term immunity as they provide the immune system with a “memory” of past infections, enabling a faster and more efficient response if the same pathogen is encountered again.
6. Phagocytes and Lymphocytes in Blood Samples
a. Describe how the structure of a phagocyte differs from the structure of a lymphocyte.
Answer: Phagocytes typically have a lobed nucleus and contain numerous lysosomes for digesting pathogens. They also possess a larger quantity of cytoplasm compared to lymphocytes. In contrast, lymphocytes have a more rounded nucleus and less cytoplasm.
Study Note: Phagocytes are specialized for engulfing and destroying pathogens, which is reflected in their structural features like the lobed nucleus and abundant lysosomes. Lymphocytes, involved in adaptive immunity, have a structure optimized for recognizing specific antigens and coordinating immune responses.
b. Describe what happens to T-lymphocytes during an immune response to measles.
Answer: During an immune response to measles, antigen-presenting cells (APCs) like macrophages present measles antigens to T-lymphocytes. Specific T-lymphocytes with receptors complementary to the antigens are selected and activated. These activated T cells undergo clonal expansion through mitosis, increasing their numbers. Helper T cells secrete cytokines to activate B-lymphocytes, which produce antibodies, while cytotoxic T cells target and destroy infected host cells, preventing the spread of the virus.
Study Note: T-lymphocytes play a critical role in orchestrating the immune response. Helper T cells aid in activating other immune cells, whereas cytotoxic T cells directly eliminate infected cells, ensuring a comprehensive defense against pathogens like the measles virus.
c. State how the response of B-lymphocytes during an immune response is different from the response of T-lymphocytes.
Answer: B-lymphocytes are activated by the presence of antigens and differentiate into plasma cells that secrete antibodies specific to those antigens. In contrast, T-lymphocytes do not secrete antibodies; instead, they either help activate other immune cells (Helper T cells) or directly kill infected cells (Cytotoxic T cells).
Study Note: While both B and T cells are essential for adaptive immunity, their functions diverge: B cells handle the production of antibodies for neutralizing pathogens, whereas T cells manage cell-mediated responses and help coordinate the overall immune response.
7. Measles and Immunity
a.
- i. Explain the term passive immunity.
- ii. How do babies gain passive immunity?
i. Explain the term passive immunity.
Answer: Passive immunity is the acquisition of antibodies from another source rather than through the individual’s own immune system.
Study Note: Unlike active immunity, which involves the body’s own immune response to an antigen, passive immunity provides immediate but temporary protection by transferring antibodies from another individual or through biological materials like breast milk.
ii. How do babies gain passive immunity?
Answer: Babies gain passive immunity through the transfer of antibodies from their mothers, either across the placenta during pregnancy or through breast milk after birth.
Study Note: This transfer of maternal antibodies provides newborns with protection against various pathogens during the early months of life, bridging the gap until their own immune systems become fully functional.
b.
- i. Explain why the vaccine for measles should not be given too early.
- ii. Explain why measles has not been eradicated, even though a vaccine has existed since the 1960s.
i. Explain why the vaccine for measles should not be given too early.
Answer: Giving the measles vaccine too early can be ineffective because maternal antibodies present in the baby can neutralize the vaccine before it stimulates the baby’s immune system to develop its own active immunity. This prevents the formation of memory cells and long-term protection.
Study Note: Timing of vaccination is crucial to ensure that the vaccine can effectively engage the infant’s immune system without interference from maternal antibodies, thereby ensuring the development of lasting immunity.
ii. Explain why measles has not been eradicated, even though a vaccine has existed since the 1960s.
Answer: Measles remains prevalent due to factors such as insufficient vaccination coverage, vaccine hesitancy, and challenges in reaching all populations globally. Additionally, measles is highly contagious, making it difficult to contain outbreaks without widespread immunization efforts.
Study Note: Eradication of a disease like measles requires comprehensive and consistent vaccination programs, global cooperation, and addressing barriers to vaccine access and acceptance to achieve herd immunity.
c. Explain how vaccination was used in the eradication of smallpox.
Answer: Vaccination campaigns for smallpox involved mass immunization of populations to achieve herd immunity, preventing the spread of the virus. Strategies included surveillance to identify and isolate infected individuals, ring vaccination to target those exposed to the virus, and the use of a stable, effective vaccine that provided lifelong immunity. Global coordination ensured that even remote and vulnerable populations were reached, ultimately leading to the complete eradication of smallpox by the late 1970s.
Study Note: The eradication of smallpox is a landmark achievement in public health, demonstrating the effectiveness of coordinated global vaccination efforts, robust surveillance systems, and the deployment of efficient vaccination strategies to eliminate a deadly disease.
8. Antibody Molecule Structure
a. Describe briefly how antibody molecules are produced and secreted.
Answer: Antibody production begins with the transcription of DNA into messenger RNA (mRNA) in B-lymphocytes. This mRNA is then translated into amino acids to form four polypeptide chains, which assemble into a Y-shaped antibody molecule. The assembled antibodies are packaged in the Golgi apparatus into vesicles and secreted from the cell via exocytosis.
Study Note: The process of antibody synthesis involves gene expression (transcription and translation) and protein assembly within B cells, culminating in the secretion of antibodies that play a key role in identifying and neutralizing antigens.
b.
- i. Name the regions X and Y.
- ii. Name the bond labeled z.
i. Name the regions X and Y.
Answer:
- X: Variable region (antigen-binding site)Y: Constant region
Study Note: The variable regions of an antibody are responsible for binding to specific antigens, allowing for targeted immune responses. The constant regions interact with other components of the immune system, such as phagocytes, to facilitate the elimination of pathogens.
ii. Name the bond labeled z.
Answer: Disulfide bond
Study Note: Disulfide bonds are strong covalent bonds that link the heavy and light chains of an antibody, maintaining its structural integrity and enabling the proper formation of the Y-shaped molecule.
c. Explain how the structure of an antibody is related to its function.
Answer: The Y-shaped structure of an antibody allows it to simultaneously bind to two identical antigens through its two variable regions, increasing binding strength and specificity. The hinge region provides flexibility, enabling the antibody to adapt to various shapes of antigens. The constant regions interact with immune cells, facilitating processes like phagocytosis and complement activation. This structural arrangement ensures that antibodies effectively recognize and neutralize pathogens while coordinating with other components of the immune system to eliminate threats.
Study Note: The unique structure of antibodies is intricately linked to their ability to recognize specific antigens and engage other immune mechanisms, making them powerful tools in the body’s defense against infections.