Nokea
What role do cytokines play in innate immunity?
- A. They directly kill pathogens
- B. They act as signaling molecules to coordinate immune responses
- C. They only function in adaptive immunity
- D. They inhibit phagocytosis
Correct Answer: B
Rationale: The correct answer is B because cytokines act as signaling molecules to coordinate immune responses in innate immunity. They help regulate inflammation, activate immune cells, and promote clearance of pathogens. Option A is incorrect because cytokines do not directly kill pathogens. Option C is incorrect as cytokines play a crucial role in both innate and adaptive immunity. Option D is incorrect because cytokines do not inhibit phagocytosis; instead, they enhance this process to help eliminate pathogens.
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What is hyperkalemia frequently associated with?
- A. Hypoglycemia
- B. Metabolic acidosis
- C. Respiratory alkalosis
- D. Decreased urine potassium levels
Correct Answer: B
Rationale: Metabolic acidosis increases hydrogen ion exchange for potassium in cells, releasing potassium into the bloodstream and causing hyperkalemia.
Choose the correct sequence in an allergic reaction.
- A. Allergen → mast cells → histamine → B cells → IgE antibodies
- B. Allergen → IgE antibodies → B cells → histamine → mast cells
- C. Allergen → B cells → IgE antibodies → mast cells → histamine
- D. Allergen → histamine → mast cells → IgE antibodies → B cells
Correct Answer: C
Rationale: Rationale for Answer C:
1. Allergen exposure triggers B cells to produce IgE antibodies specific to the allergen.
2. IgE antibodies bind to mast cells sensitizing them.
3. Upon re-exposure to allergen, allergen binds to IgE on mast cells.
4. This triggers release of histamine and other chemicals causing allergic symptoms.
Summary:
- Choice A: Incorrect because B cells do not produce IgE antibodies before allergen exposure.
- Choice B: Incorrect because IgE antibodies are produced by B cells, not the other way around.
- Choice D: Incorrect because histamine is released after allergen binds to IgE on sensitized mast cells.
The reason for using Taq polymerase for PCR is that
- A. it has regions that are complementary to primers.
- B. only minute amounts are needed for each cycle of PCR
- C. it binds more readily than other polymerases to primer.
- D. it is heat stable and can withstand the temperature changes of the cycler.
Correct Answer: D
Rationale: The correct answer is D because Taq polymerase is heat-stable, allowing it to withstand the high temperatures used in PCR cycles without denaturing. This heat stability is crucial for the repeated heating and cooling cycles in PCR. Choice A is incorrect because Taq polymerase does not need to be complementary to primers. Choice B is incorrect because the amount needed is not the main reason for using Taq polymerase. Choice C is incorrect because binding affinity to primers is not the primary reason for using Taq polymerase.
Compared to antibodies produced in a primary response to a given antigen, the antibodies produced in a memory response are typically:
- A. More likely to be IgM
- B. More likely to be IgG, IgA and/or IgE
- C. Of lower affinity
- D. Two of these responses are correct
Correct Answer: B
Rationale: Step 1: Memory response produces antibodies of higher affinity due to affinity maturation.
Step 2: Memory response involves class switching, leading to production of IgG, IgA, and IgE.
Step 3: IgM is predominant in primary response, but memory response shifts towards other classes.
Summary: Choice B is correct as memory response produces antibodies of higher affinity and different classes. Choices A and C are incorrect as memory response does not typically result in more IgM or lower affinity antibodies. Choice D is incorrect as only choice B is accurate.
Which part of an antibody determines its antigen specificity?
- A. Fc fragment
- B. Fab region
- C. Heavy chain constant region
- D. Light chain constant region
Correct Answer: B
Rationale: The correct answer is B: Fab region. The Fab region of an antibody contains the antigen-binding site, where specific interactions with antigens occur. This region is formed by the variable regions of both the heavy and light chains. The Fc fragment (choice A) is responsible for effector functions, not antigen specificity. The heavy chain constant region (choice C) and light chain constant region (choice D) are not involved in antigen binding, but rather provide structural support and determine the antibody class. Therefore, the Fab region is crucial for antigen specificity due to its variable regions that directly interact with antigens.