The basic structure of an antibody molecule is

Correct Answer: B

Rationale: Rationale for Answer B: 1. Antibody structure consists of two identical heavy chains and two identical light chains. 2. These chains are covalently linked to form the Y-shaped structure of an antibody. 3. Each chain contributes to the formation of antigen-binding sites. 4. Therefore, two identical heavy chains and two identical light chains form two antigen-binding sites. Summary of Incorrect Choices: A: Incorrect because it describes only one antigen-binding site formed by one light chain and one heavy chain. C: Incorrect because it describes one antigen-binding site formed by two identical heavy chains and two identical light chains. D: Incorrect because it incorrectly describes the roles of light and heavy chains in antibody structure.

Correct Answer: D

Rationale: The correct answer is D: All above. The vibrations from sound waves are amplified by the eardrum, Anvil (also known as the Incus), and Stirrup (also known as the Stapes), which are the three tiny bones in the middle ear. The sound waves travel through the ear canal and hit the eardrum, causing it to vibrate. The vibration is then transmitted through the Anvil to the Stirrup, which amplifies the vibrations and sends them to the inner ear. Each of these three components plays a crucial role in the process of amplifying sound vibrations for better auditory perception. Therefore, all three choices are correct in this context.

Correct Answer: B

Rationale: The correct answer is B: Thrombocytopenia, which refers to an abnormal decrease in platelets. Platelets are crucial for blood clotting. Leukopenia (A) is a decrease in white blood cells, not platelets. Anemia (C) is a decrease in red blood cells, not platelets. Hemolysis (D) is the breakdown of red blood cells, not related to platelet count. Therefore, B is the correct answer as it specifically addresses a decrease in platelet count, leading to potential bleeding issues.

Correct Answer: B

Rationale: The correct answer is B, the discovery that cell-free serum could transfer immunity. This finding led humoralists to dominate because it supported the idea of circulating antibodies in the serum being responsible for immunity. This concept aligned with the humoralist theory, which focused on the role of antibodies in immune response. The ability of cell-free serum to transfer immunity provided direct evidence for humoralists' beliefs. Choice A (The demonstration of the Germ Theory of disease) is incorrect because while it was a significant advancement in understanding disease, it did not directly impact the argument between cellularists and humoralists regarding the immune response. Choice C (The discovery of the tuberculin reaction) is incorrect as it was more relevant to the understanding of the immune response to tuberculosis specifically, rather than the broader debate between cellularists and humoralists. Choice D (The determination of the antibody structure) is incorrect because while understanding antibody structure is crucial, it did not have as direct an impact on the dominance of

Correct Answer: C

Rationale: The correct answer is C: To the nucleus. When macrophages are stimulated with LPS, NFkB is activated and translocates to the nucleus. In the nucleus, NFkB regulates the expression of genes involved in the inflammatory response. Choices A, B, and D are incorrect because NFkB does not primarily move to the cytoplasm, phagosomes, or cell membrane in response to LPS stimulation in macrophages.