Normal adult Hb A contains which polypeptide chains?

Correct Answer: A

Rationale: The correct answer is A: Alpha and beta. Hemoglobin A in normal adults consists of two alpha and two beta globin polypeptide chains. This is the most common form of hemoglobin in adults. The other choices (B: Alpha and epsilon, C: Alpha and delta, D: Alpha and brotherton) are incorrect because epsilon, delta, and brotherton are not the typical polypeptide chains found in adult hemoglobin. Hemoglobin F contains gamma and alpha chains, not epsilon or delta. Brotherton is not a known polypeptide chain in hemoglobin.

Correct Answer: B

Rationale: The correct answer is B: Glutathione reduction. NADPH generated from the pentose phosphate pathway in RBCs is crucial for maintaining reduced glutathione levels, which helps protect cells from oxidative damage. Glutathione is an important antioxidant in cells that helps neutralize harmful reactive oxygen species. This process is essential for the protection of RBCs from oxidative stress and maintains their structural integrity. A: Fatty acid synthesis - NADPH is indeed required for fatty acid synthesis, but in RBCs, the primary role of NADPH is in maintaining redox balance rather than fatty acid synthesis. C: ATP formation - NADPH is not directly involved in ATP formation, as ATP is mainly produced through processes like glycolysis and oxidative phosphorylation. D: Oxygen radical removal - While NADPH is involved in reducing oxidative stress, its primary role in RBCs is to maintain glutathione levels for antioxidant defense rather than directly removing oxygen radicals.

Correct Answer: C

Rationale: Schistocytes are fragmented red blood cells formed due to mechanical trauma in the circulation. In the context of microangiopathic hemolytic anemia (MAHA), such as in thrombotic thrombocytopenic purpura or hemolytic uremic syndrome, schistocytes are commonly seen due to the presence of microthrombi in small vessels. This mechanical destruction of red blood cells leads to the characteristic appearance of schistocytes on peripheral blood smear. Therefore, the correct answer is C. Sickle cell trait (choice A) and thalassemia (choice B) do not typically present with schistocytes. In immune thrombocytopenic purpura (ITP) (choice D), the destruction of platelets by autoantibodies does not typically cause schistocytes formation.

Correct Answer: A

Rationale: The correct answer is A: Phlebotomus species. Visceral leishmaniasis is transmitted by sandflies of the genus Phlebotomus in Asia. These sandflies are the main vectors for the parasite that causes the disease. Phlebotomus species are known to transmit Leishmania donovani, the causative agent of visceral leishmaniasis. Lutzomyia species (B) are primarily found in the Americas and are more commonly associated with cutaneous leishmaniasis. Anopheles species (C) are known vectors for malaria, not visceral leishmaniasis. Mansonia species (D) are associated with transmitting various viruses, not Leishmania parasites. Therefore, the correct answer is A as Phlebotomus species are the main vectors of visceral leishmaniasis in Asia.

Correct Answer: C

Rationale: The correct answer is C: IgG. IgG is the major immunoglobulin in human serum, comprising about 80% of the pool. IgA is mainly found in mucosal secretions, IgD is involved in B cell activation, and IgM is the first antibody produced in response to an infection. IgG is the most abundant and versatile immunoglobulin, providing long-term immunity through neutralization, opsonization, and complement activation. Its high concentration in serum makes it crucial for defending against various pathogens.