Normal Adult Hb A contains the following polypeptide chains:

Correct Answer: A

Rationale: Step 1: Normal Adult Hb A is composed of two alpha and two beta globin chains. Step 2: Hemoglobin A is the most common type of hemoglobin in adults. Step 3: The correct answer, A, is alpha and beta, as confirmed in step 1. Step 4: Choice B is incorrect as epsilon is not a component of Adult Hb A. Step 5: Choice C is incorrect as delta is not a component of Adult Hb A. Step 6: Choice D is incorrect as brotherton is not a known component of hemoglobin.

Correct Answer: B

Rationale: The correct answer is B: Ferrous. In the heme molecule, iron is present in the ferrous form (Fe2+). This form of iron allows for the binding of oxygen in hemoglobin. Ferro (A) is not a correct term for iron in heme. Ferric (C) refers to the Fe3+ form of iron, which is not found in heme. Apoferritin (D) is a protein that stores iron but is not directly involved in heme synthesis. Therefore, the correct form of iron in the heme molecule is ferrous (B).

Correct Answer: B

Rationale: The correct answer is B: Monoclonal protein in serum or urine. Multiple myeloma is characterized by the presence of abnormal plasma cells in the bone marrow, which produce monoclonal proteins. These proteins can be detected in the blood or urine through electrophoresis. Fever and infection (Choice A) are common symptoms but not specific to multiple myeloma. Elevated platelet count (Choice C) is not a characteristic feature of multiple myeloma. Normal bone marrow (Choice D) is not consistent with the disease, as multiple myeloma involves abnormal plasma cell proliferation in the bone marrow.

Correct Answer: B

Rationale: The correct answer is B because the principal difference between cytotoxic (type II) and immune complex (type III) hypersensitivity lies in the site where antigen-antibody complexes are formed. In type II hypersensitivity, the complexes form on the surface of target cells, leading to cell destruction. In contrast, in type III hypersensitivity, the complexes form in circulation or in tissues, leading to immune complex deposition and subsequent tissue damage. The other choices are incorrect because the class of antibody (A), participation of complement (C), and participation of T cells (D) can be common features in both type II and type III hypersensitivity reactions, but the crucial distinguishing factor is where the complexes are formed.

Correct Answer: C

Rationale: The correct answer is C because AIDS is caused by the human immunodeficiency virus (HIV), which specifically targets and kills CD4-positive T lymphocytes. These cells are crucial for coordinating the immune response. A, B, and D are incorrect because HIV primarily affects CD4-positive T cells, not B lymphocytes, lymphocyte stem cells, or CD8-positive T cells. This leads to a weakened immune system, making individuals more susceptible to infections and other complications associated with AIDS.