Nokea
Which of the following is NOT a function of the immune system?
- A. Promoting wound healing
- B. Fighting cancer
- C. Increasing pathogen reproduction
- D. Eliminating cell debris
Correct Answer: C
Rationale: The correct answer is C: Increasing pathogen reproduction. The immune system's main function is to protect the body from pathogens and foreign invaders, not to promote their reproduction. A: Promoting wound healing is correct as the immune system helps in tissue repair. B: Fighting cancer is correct as the immune system plays a role in recognizing and destroying cancerous cells. D: Eliminating cell debris is correct as the immune system helps in clearing out dead or damaged cells to maintain tissue health.
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What is the process called when a specific lymphocyte binds its antigen and proliferates?
- A. Clonal deletion
- B. Clonal selection
- C. Antigen presentation
- D. Cytokine signaling
Correct Answer: B
Rationale: The correct answer is B: Clonal selection. During clonal selection, a specific lymphocyte recognizes its specific antigen, binds to it, and undergoes proliferation to generate a large population of identical cells to combat the antigen efficiently. This process ensures an effective immune response.
Incorrect choices:
A: Clonal deletion - This process involves the elimination of self-reactive lymphocytes to prevent autoimmunity, not the proliferation of antigen-specific lymphocytes.
C: Antigen presentation - This is the process by which antigens are displayed to immune cells for recognition, not the proliferation of lymphocytes.
D: Cytokine signaling - While cytokines play a role in immune responses, they are not directly involved in the proliferation of lymphocytes in response to specific antigens.
What was the important contribution to microbiology of Anton Van Leeuwenhoek in the 1600s?
- A. He was the first to observe microorganisms
- B. He disproved the theory of spontaneous generation of microorganisms
- C. He was the first to show that a disease could be caused by a microorganism
- D. He was the first to describe the process of fermentation
Correct Answer: A
Rationale: The correct answer is A: He was the first to observe microorganisms. Van Leeuwenhoek's important contribution to microbiology was his discovery of microorganisms using his own handcrafted microscopes. This observation revolutionized the field by providing the first direct evidence of the existence of microorganisms.
Choice B is incorrect because Leeuwenhoek's observations actually supported the idea of spontaneous generation. Choice C is incorrect because he did not link microorganisms to diseases. Choice D is incorrect because the process of fermentation was described by others before Leeuwenhoek.
Identify the mismatched receptor: ligand pair
- A. NOD2: peptidoglycan
- B. TLR9: CpG DNA
- C. TLR5: dsRNA
- D. RIG-I: viral RNA
Correct Answer: C
Rationale: TLR5 recognizes flagellin, not dsRNA. This is why choice C is the correct answer. NOD2 binds to peptidoglycan (A), TLR9 binds to CpG DNA (B), and RIG-I recognizes viral RNA (D). Each receptor has specificity for a different ligand, making choice C the mismatched pair.
Identify the incorrect statement in regard to immunoglobulins (Ig)
- A. Are made up of two identical light chains and two identical heavy chains
- B. Cannot recognize conformational antigens on viral particles
- C. Can recognize only exposed epitopes of pathogens
- D. Expressed early during B cell development on the membrane of B cell precursors (pre- B cells)
Correct Answer: B
Rationale: The correct answer is B because immunoglobulins can indeed recognize conformational antigens on viral particles. Immunoglobulins have variable regions that can bind to a wide range of antigen shapes. Choice A is correct as Ig structure consists of two light and two heavy chains. Choice C is incorrect as immunoglobulins can also bind to internal epitopes. Choice D is incorrect as Ig expression starts during the late B cell development stage.
DNA ligase catalyzes reactions that facilitate the formation of
- A. ester bonds
- B. DNA ligase
- C. phosphohydroxyl bonds
- D. amide bonds
Correct Answer: B
Rationale: DNA ligase catalyzes the formation of phosphodiester bonds between the sugar-phosphate backbone of DNA strands. The correct answer is B because DNA ligase specifically acts on these phosphodiester bonds to seal nicks in the DNA molecule during processes like DNA replication and repair. Option A, ester bonds, are not formed by DNA ligase. Option C, phosphohydroxyl bonds, is not a recognized type of bond in DNA ligation. Option D, amide bonds, are not formed by DNA ligase either. Thus, the correct answer is B as it aligns with the known function of DNA ligase.