Nokea
What are characteristics of the phosphate buffer system (select all that apply)?
- A. Neutralizes a strong base to a weak base and water
- B. Resultant sodium biphosphate is eliminated by kidneys
- C. Free acid radicals dissociate into H+ and CO2,buffering excess base
- D. Neutralizes a strong acid to yield sodium biphosphate,a weak acid and salt
Correct Answer: B
Rationale: Phosphate buffers neutralize strong bases/acid, form sodium biphosphate, and eliminate it through the kidneys.
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Which of the following statements is NOT true
- A. Light chains isotypes are functionally different
- B. The antigen binding site of a B cell receptor is identical to the antigen binding site of antibodies secreted by the same B cell
- C. Both heavy and light chain domains assume a compact barrel structure
- D. The hinge region assumes a more open and flexible structure
Correct Answer: A
Rationale: The correct answer is A: Light chains isotypes are functionally different. This statement is NOT true because light chain isotypes (kappa and lambda) have distinct primary structures but serve the same function in antigen binding. The heavy chain determines the effector function of antibodies. The other choices are correct: B) The antigen binding site of a B cell receptor is identical to the antigen binding site of antibodies secreted by the same B cell, as both use the same variable regions for antigen recognition. C) Both heavy and light chain domains assume a compact barrel structure, which is essential for antibody stability and function. D) The hinge region assumes a more open and flexible structure, allowing antibodies to bind antigens at different orientations.
One principal function of the Class I and Class II major histocompatibility complex S proteins is to
- A. transduce the signal to the T-cell interior following antigen binding
- B. mediate immunoglobulin class switching
- C. present antigen for recognition by the T-cell antigen receptor
- D. stimulate production of interleukins
Correct Answer: C
Rationale: The correct answer is C because Class I and Class II MHC proteins present antigens to T-cell receptors for immune response activation. Class I MHC presents endogenous antigens to CD8+ T cells, while Class II MHC presents exogenous antigens to CD4+ T cells. Choice A is incorrect because MHC proteins do not transduce signals. Choice B is incorrect because MHC proteins do not mediate immunoglobulin class switching. Choice D is incorrect because MHC proteins do not directly stimulate interleukin production.
A major effector function of TH2 cells is:
- A. Protection against intracellular bacteria
- B. Protection against parasitic worms
- C. Regulation of the adaptive immune response through the secretion of anti-inflammatory cytokines
- D. Activation of macrophages
Correct Answer: B
Rationale: The correct answer is B because TH2 cells play a crucial role in protecting against parasitic worms by secreting cytokines that promote eosinophil activation and antibody production. This response helps to expel the parasites from the body.
Incorrect choices:
A: TH1 cells are responsible for protection against intracellular bacteria.
C: TH3 cells, not TH2 cells, are known for secreting anti-inflammatory cytokines.
D: Activation of macrophages is primarily mediated by TH1 cells through IFN-gamma secretion.
NOD2
- A. Is a cytosolic receptor for bacteria
- B. Is mutated in 30% of patients with Crohn's disease
- C. Activates NFκB
- D. All of the above is correct
Correct Answer: D
Rationale: Step-by-step rationale:
1. NOD2 is a cytosolic receptor for bacteria, detecting bacterial molecules.
2. Mutations in NOD2 are found in 30% of patients with Crohn's disease.
3. NOD2 activation triggers NFκB signaling pathway.
4. Therefore, all the statements (A, B, C) are correct, making option D the correct answer. Other choices are incorrect as they do not encompass all the correct statements about NOD2.
What drives the emergence of immuno-resistant pathogen strains?
- A. Host immune system failure
- B. Slow mutation rates in pathogens
- C. Rapid pathogen reproduction and mutations
- D. Absence of host immune adaptation
Correct Answer: C
Rationale: The correct answer is C: Rapid pathogen reproduction and mutations drive the emergence of immuno-resistant pathogen strains. This is because the high rate of reproduction allows for more opportunities for mutations to occur, some of which may confer resistance to the host's immune system or medical interventions. Slow mutation rates in pathogens (B) would not lead to the rapid emergence of resistant strains. Host immune system failure (A) occurs after the pathogen has already developed resistance. The absence of host immune adaptation (D) does not directly drive the emergence of resistant strains as it is the rapid reproduction and mutations of pathogens that play a crucial role.