Nokea
T-cell receptors or antibodies react with antigens
- A. because both are made by lymphocytes
- B. because of complementary of molecular fit of both with antigen
- C. because both have light chain and heavy chain polypeptides
- D. cause histamine release
Correct Answer: B
Rationale: The correct answer is B because T-cell receptors and antibodies recognize antigens through complementary molecular fit. This interaction is based on the specific shape of the antigen-binding site on the receptor or antibody matching the shape of the antigen. This molecular complementarity allows for strong and specific binding between the antigen and the receptor/antibody. Choices A and C are incorrect as the presence of lymphocytes or specific polypeptide chains alone does not explain the mechanism of antigen recognition. Choice D is incorrect because histamine release is not directly related to the interaction between T-cell receptors or antibodies with antigens.
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A patient is taking diuretic drugs that cause sodium loss from the kidney. Which fluid or electrolyte imbalance is most likely to occur in this patient?
- A. Hyperkalemia
- B. Hyponatremia
- C. Hypocalcemia
- D. Hypotonic fluid loss
Correct Answer: B
Rationale: Diuretics promote sodium excretion, leading to hyponatremia as more water follows sodium out of the body.
Patients with rheumatoid arthritis typically have pain:
- A. With activity.
- B. Upon awakening.
- C. Late in the evening.
- D. All day without remission.
Correct Answer: B
Rationale: Rheumatoid arthritis often causes morning stiffness and pain upon awakening due to inflammation and lack of movement during sleep. Pain tends to improve with activity as joints warm up.
What is the main role of neutrophils in the immune response?
- A. Producing antibodies
- B. Engulfing and destroying pathogens
- C. Activating lymphocytes
- D. Synthesizing cytokines
Correct Answer: B
Rationale: Neutrophils play a crucial role in the immune response by engulfing and destroying pathogens through a process called phagocytosis. This is essential for eliminating harmful invaders from the body. Neutrophils do not produce antibodies (choice A), activate lymphocytes (choice C), or synthesize cytokines (choice D), which are functions typically carried out by other immune cells like B cells and macrophages. Therefore, the correct answer is B as it directly aligns with the primary function of neutrophils in the immune response, which is to combat infections by destroying pathogens.
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.
Protective immunity against Leishmania is best in individuals that make a:
- A. Strong antibody response
- B. Response that activates macrophages
- C. Response that activates mast cells
- D. Strong anti-bacterial response
Correct Answer: B
Rationale: The correct answer is B: Response that activates macrophages. Macrophages play a crucial role in controlling Leishmania infection by phagocytizing the parasites. Activating macrophages enhances their ability to kill the intracellular parasites, leading to effective immunity. Antibodies (choice A) are not as effective against intracellular pathogens like Leishmania. Mast cells (choice C) are primarily involved in allergic reactions, not protective immunity against parasites. Anti-bacterial response (choice D) is not directly relevant to combating Leishmania, an intracellular parasite.