What is the function of G6PD? (35-year-old male with G6PD deficiency)

Correct Answer: B

Rationale: The correct answer is B: RBC protection against oxidative damage. Glucose-6-phosphate dehydrogenase (G6PD) enzyme plays a crucial role in protecting red blood cells (RBCs) from oxidative damage by generating NADPH, which helps in neutralizing reactive oxygen species. G6PD deficiency leads to RBCs being more susceptible to oxidative stress, causing hemolysis. Choice A (Clotting factor production) is incorrect because G6PD is not directly involved in clotting factor production. Choice C (Platelet activation) is incorrect as G6PD deficiency does not affect platelet activation. Choice D (White cell proliferation) is incorrect as G6PD deficiency primarily affects RBCs, not white cell proliferation.

Correct Answer: B

Rationale: The correct answer is B: vascular permeability. C3a and C5a are anaphylatoxins that can cause increased vascular permeability, leading to fluid leakage and inflammatory responses. They do not directly cause bacterial lysis (choice A), phagocytosis of IgE-coated bacteria (choice C), or aggregation of C4 and C2 (choice D). Increased vascular permeability is a key mechanism by which these complement proteins contribute to inflammation and immune responses.

Correct Answer: D

Rationale: The correct answer is D because the genes for the gamma chain and alpha chain are located on the same chromosome, making them linked genes. This is known as genetic linkage. The other choices (A, B, C) involve genes from different chromosomes or gene segments, so they are not linked genes. Genes that are physically close together on the same chromosome tend to be inherited together, which is the basis of genetic linkage analysis.

Correct Answer: A

Rationale: Activated helper T cells release various cytokines to regulate the immune response. Interleukin-1 is primarily produced by macrophages and monocytes, not helper T cells. It plays a role in inflammation and fever. Interleukin-2, interleukin-4, and gamma interferon are indeed released by activated helper T cells to stimulate immune responses. Therefore, choice A, interleukin-1, is the correct answer as it is not typically released by activated helper T cells.

Correct Answer: B

Rationale: The correct answer is B because the antibody-binding site is primarily formed by the hypervariable regions of both the heavy (H) and light (L) chains. These regions contain the most sequence diversity and directly interact with antigens. Choice A is incorrect because the constant regions do not directly participate in antigen binding. Choice C is incorrect as it only mentions H chains, disregarding the contribution of L chains. Choice D is incorrect as it focuses solely on the variable regions of H chains, neglecting the importance of the L chains in forming the binding site.