Nokea
Which part of the antibody determines its physiological effects?
- A. Fab fragment
- B. Fc fragment
- C. Variable region
- D. Antigen-binding site
Correct Answer: B
Rationale: The correct answer is B: Fc fragment. The Fc fragment of an antibody determines its physiological effects by interacting with immune cells and other effector molecules. It mediates processes like opsonization, complement activation, and antibody-dependent cell-mediated cytotoxicity. The Fab fragment (A) contains the antigen-binding site but does not directly influence physiological effects. The variable region (C) is part of both the Fab and Fc portions and contributes to antigen specificity but does not solely determine physiological effects. The antigen-binding site (D) is located within the Fab portion and is responsible for binding to specific antigens, not for exerting physiological effects.
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Which cell type bridges innate and adaptive immunity?
- A. NK cells
- B. Dendritic cells
- C. Plasma cells
- D. Mast cells
Correct Answer: B
Rationale: The correct answer is B: Dendritic cells. Dendritic cells bridge innate and adaptive immunity by capturing antigens, processing them, and presenting them to T cells to initiate adaptive immune responses. NK cells (A) are part of innate immunity, while plasma cells (C) produce antibodies in adaptive immunity. Mast cells (D) are involved in allergic responses, not bridging innate and adaptive immunity.
A nurse is teaching the client with systemic lupus erythematosus about prednisone. What information is the priority?
- A. Might make the client feel jittery or nervous.
- B. Can cause sodium and fluid retention.
- C. Long-term effects include fat redistribution.
- D. Never stop prednisone abruptly.
Correct Answer: D
Rationale: The correct answer is D because abruptly stopping prednisone can lead to adrenal insufficiency due to suppression of the body's natural cortisol production. Adrenal insufficiency can be life-threatening. Priority is given to this information to ensure the client's safety. Choice A is incorrect as jitteriness or nervousness are common side effects but not the priority. Choice B is incorrect as sodium and fluid retention are potential side effects but not as critical as avoiding adrenal insufficiency. Choice C is incorrect as fat redistribution is a long-term effect but not as immediate as the risk of adrenal insufficiency.
The dark zone of germinal centers (GC) is composed of
- A. Rapidly proliferating B cells
- B. T cells and dendritic cells
- C. Rapidly proliferating T cells
- D. Follicular dendritic cells
Correct Answer: A
Rationale: The dark zone of germinal centers is composed of rapidly proliferating B cells. This is because during the dark zone phase of the germinal center reaction, B cells undergo rapid proliferation and somatic hypermutation to generate high-affinity antibodies. T cells and dendritic cells are typically found in the light zone of the germinal centers where B cells interact with them to receive signals for selection. Rapidly proliferating T cells are not typically found in the dark zone. Follicular dendritic cells are present in the light zone where they present antigens to B cells but not in the dark zone where B cell proliferation mainly occurs.
Which enzyme catalyzes the following reaction? Gap 5' - G G-A-T-C-C—3' ⋮ ⋮ ⋮ ⋮ ⋮ 3' - C-C-T-A-G G—5' Gap 5' - G-G-A-T-C-C—3' ⋮ ⋮ ⋮ ⋮ ⋮ 3' - C-C-T-A-G-G—5'
- A. DNA ligase
- B. DNA endonuclease
- C. None of the options are correct
- D. DNA polymerase 1
Correct Answer: A
Rationale: The correct answer is A: DNA ligase. DNA ligase catalyzes the joining of two DNA strands by forming a phosphodiester bond between the 3' hydroxyl of one nucleotide and the 5' phosphate of another. In the given reaction, the enzyme is needed to seal the nick in the DNA strands after the Okazaki fragments have been synthesized during DNA replication.
Explanation of other choices:
B: DNA endonuclease - Endonucleases cleave the phosphodiester bond within a polynucleotide chain, not join two DNA strands.
C: None of the options are correct - This is incorrect as DNA ligase is the correct enzyme for this reaction.
D: DNA polymerase 1 - DNA polymerase synthesizes new DNA strands by adding nucleotides to the 3' end of the growing chain, not joining two DNA strands.
Which of the following statements concerned with the microbiota is NOT true?
- A. It colonizes our body at birth
- B. Its composition in adults is influenced by several factors, including diet and exercise
- C. Obesity is associated with alterations in the composition of gut microbiota. This condition has been shown to be transmissible in mice when microbiota from obese mice is transferred to lean mice
- D. Bacteria found in obese mice are less efficient at extracting energy from food and this in turn impacts on the sense of satiety of the animal.
Correct Answer: D
Rationale: The correct answer is D because it is the only statement that is not entirely true regarding the microbiota. The rationale for this is that bacteria found in obese mice are actually more efficient at extracting energy from food, not less efficient as mentioned in option D. This increased efficiency contributes to the higher energy extraction from food, leading to weight gain in obese individuals. The other options (A, B, C) are correct as they align with current research and understanding of the microbiota. Option A is true as the microbiota begins to colonize our body at birth. Option B is also true as the composition of the microbiota in adults can indeed be influenced by various factors such as diet and exercise. Option C is true as obesity has been linked to alterations in gut microbiota composition, and studies have shown that transferring microbiota from obese to lean mice can induce weight gain in the lean mice.