Which of the following statements is NOT true

Correct Answer: A

Rationale: The correct answer is A: Light chains isotypes are functionally different. This statement is NOT true because light chain isotypes (kappa and lambda) have distinct primary structures but serve the same function in antigen binding. The heavy chain determines the effector function of antibodies. The other choices are correct: B) The antigen binding site of a B cell receptor is identical to the antigen binding site of antibodies secreted by the same B cell, as both use the same variable regions for antigen recognition. C) Both heavy and light chain domains assume a compact barrel structure, which is essential for antibody stability and function. D) The hinge region assumes a more open and flexible structure, allowing antibodies to bind antigens at different orientations.

Correct Answer: A

Rationale: The correct answer is A: Food chains. A food chain depicts the flow of energy and nutrients from one organism to another in an ecosystem. It shows how energy is transferred from producers to consumers. Food network (B) is a more complex and interconnected system than a simple linear chain. Pyramid of power (C) represents the energy flow in an ecosystem, not the transfer of food. Levels of nutrition (D) is not a term commonly used to describe how organisms transfer food and energy.

Correct Answer: A

Rationale: The correct answer is A: Thrombosis. Thrombosis refers to the formation of a blood clot within a blood vessel. The process involves the coagulation of blood components to form a clot. This can lead to blockages in blood vessels, potentially causing serious health issues like stroke or heart attack. Choice B: Embolus refers to a blood clot that has traveled from its original site and lodged in a different blood vessel. Choice C: Hemorrhage is the medical term for bleeding. Choice D: Hemostasis refers to the body's process of stopping bleeding, not the formation of a blood clot.

Correct Answer: C

Rationale: Rationale: 1. Clonal selection theory states that specific lymphocytes are activated by antigens. 2. Upon activation, these lymphocytes proliferate to form a clone of cells specific to the antigen. 3. This increases the number of lymphocytes specific for the antigen. 4. Choice C correctly aligns with the essence of clonal selection theory. Summary: A: Incorrect - Clonal selection theory does not involve a single lymphocyte expressing multiple antigen receptors. B: Incorrect - Antigens do not influence the generation of antigen receptors, but rather activate specific lymphocytes. D: Incorrect - Clonal selection theory focuses on lymphocyte response to antigens, not neutrophil increase during infections.

Correct Answer: C

Rationale: TLR-3 detects viruses in endosomes. When a virus enters a host cell, it is often engulfed into endosomes. TLR-3 recognizes viral RNA within endosomes and triggers an immune response. Choices A and B are incorrect because TLR-3 does not detect viruses in the cytosol or extracellular space. Choice D is incorrect because TLR-3 specifically functions in endosomes to detect viral RNA.