What is NOT true about innate immunity?

Correct Answer: B

Rationale: The correct answer is B because innate immune cells do not respond better and faster at a second encounter with the same pathogen. This is a characteristic of adaptive immunity, not innate immunity. During a second encounter, adaptive immune cells produce a faster and stronger response due to memory cells formed during the initial exposure. In contrast, innate immune cells do not have memory cells and their response remains the same upon repeated encounters. Choice A is correct as innate cells are immediately active and do not require clonal amplification or differentiation. Choice C is correct as innate receptors recognize broad structures on pathogens. Choice D is correct as innate receptors can recognize modified-self, such as in autoimmune diseases.

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: C

Rationale: The correct answer is C: Ethylene. Ethylene is indeed a gaseous plant hormone produced during the combustion of natural gas. It plays a crucial role in various plant processes such as fruit ripening, senescence, and stress responses. A: Auxin is not a gaseous hormone and is primarily involved in promoting cell elongation and root growth. B: Gibberellins are not gaseous hormones and mainly regulate plant growth processes like stem elongation and seed germination. D: The statement "All above" is incorrect as auxin and gibberellins are not gaseous hormones, only ethylene fits the description. Therefore, choice C, Ethylene, is the correct answer as it is the gaseous by-product of natural gas combustion and a plant hormone.

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.