Nokea
Memory T cells
- A. Recirculate through blood and secondary lymphoid tissues
- B. Have never encountered antigen
- C. Have a lower threshold of activation than naïve T cells
- D. Have a higher frequency than their naïve counterparts
Correct Answer: C
Rationale: The correct answer is C because memory T cells have a lower threshold of activation than naïve T cells. This is because memory T cells have already been primed by previous exposure to antigens, making them more responsive upon re-exposure. This heightened sensitivity allows memory T cells to mount a faster and stronger immune response upon encountering the same antigen again.
Choice A is incorrect because memory T cells primarily reside in peripheral tissues and not in secondary lymphoid tissues. Choice B is incorrect because memory T cells have encountered antigens before. Choice D is incorrect because memory T cells exist in a lower frequency compared to naïve T cells due to clonal expansion during the primary immune response.
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The inflammatory response produced
- A. by microbial-infected cells
- B. Internal tissue injury
- C. migration of erythrocyts from the spleen
- D. All above
Correct Answer: D
Rationale: The correct answer is D. The inflammatory response can be triggered by microbial-infected cells releasing cytokines, internal tissue injury leading to the release of inflammatory mediators, and the migration of erythrocytes from the spleen in response to inflammation. Therefore, all of the choices - A, B, and C - are correct in contributing to the inflammatory response. Each option plays a role in the complex cascade of events that lead to inflammation.
What are haematopoietic stem cells responsible for?
- A. Differentiating into lymph nodes
- B. Producing immune cells
- C. Generating cytokines
- D. Suppressing pathogens directly
Correct Answer: B
Rationale: Haematopoietic stem cells are responsible for producing immune cells. These stem cells differentiate into various types of blood cells, including white blood cells that play a crucial role in the immune system. They do not differentiate into lymph nodes (A), generate cytokines (C), or suppress pathogens directly (D). The correct answer (B) aligns with the primary function of haematopoietic stem cells in the production of immune cells.
NAD and FAD are hydrogen carriers, but cytochromes are electron carriers in bacteria. What happens to the protons (Hâº) in electron transport chains?
- A. They go into solution inside the cytoplasm.
- B. They are taken back by NAD and FAD.
- C. They are carried from cytochromes to oxygen to form water.
- D. They go into solution outside the cytoplasmic membrane.
Correct Answer: D
Rationale: The correct answer is D because in the electron transport chain, protons (H⁺) are pumped across the membrane to create a proton gradient. This gradient is utilized by ATP synthase to produce ATP. Therefore, protons go into solution outside the cytoplasmic membrane. Choices A and B are incorrect because protons do not simply stay in the cytoplasm or get taken back by NAD and FAD. Choice C is incorrect as protons do not directly form water when carried by cytochromes.
With regard to NADPH oxidase, which of the following statements in not correct?
- A. It is the enzyme involved in the respiratory burst that follows the engagement of phagocytic receptors
- B. Individuals with mutations of NADPH oxidase subunits suffer repeated infections because of defective killing of phagocytosed pathogens
- C. It is constitutively expressed as a complex of 5 subunits in unstimulated cells
- D. It controls the formation of reactive oxygen species
Correct Answer: C
Rationale: The correct answer is C because NADPH oxidase is not constitutively expressed as a complex of 5 subunits in unstimulated cells. Instead, it is assembled and activated upon stimulation, such as during the respiratory burst following phagocytosis. Choice A is correct as NADPH oxidase is indeed involved in the respiratory burst. Choice B is correct as mutations in NADPH oxidase subunits lead to impaired pathogen killing and recurrent infections. Choice D is correct as NADPH oxidase controls the production of reactive oxygen species.
Peripheral nervous system (PNS)
- A. Located outside the CNS
- B. Consists of Nerves and Ganglia
- C. Brain & Spinal cord
- D. A& b
Correct Answer: D
Rationale: Step-by-step rationale:
1. The Peripheral Nervous System (PNS) includes nerves and ganglia, making choice B correct.
2. PNS is located outside the Central Nervous System (CNS), supporting choice A.
3. Since both A and B are accurate statements, the correct answer is D.
Summary:
- Choice A is correct because the PNS is located outside the CNS.
- Choice B is correct as the PNS includes nerves and ganglia.
- Choice C is incorrect as it refers to the CNS (Brain & Spinal cord).