Nokea
How do NK cells kill target cells?
- A. By producing antibodies
- B. Through secretion of cytokines
- C. By releasing perforin and granzyme
- D. By phagocytosis
Correct Answer: C
Rationale: The correct answer is C. NK cells kill target cells by releasing perforin and granzyme. Perforin creates pores in the target cell's membrane, allowing granzyme to enter and induce apoptosis. Antibodies (choice A) are produced by B cells, not NK cells. Cytokines (choice B) regulate immune responses but do not directly kill cells. Phagocytosis (choice D) involves engulfing and digesting pathogens, which is not how NK cells kill target cells.
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A small molecule that combines with a specific allosteric protein so that both prevent RNA polymerase activity is called a(n):
- A. inducer
- B. repressor
- C. corepressor
- D. leader
Correct Answer: C
Rationale: The correct answer is C: corepressor. A corepressor is a small molecule that binds to an allosteric protein to inhibit its activity. In this case, the corepressor prevents RNA polymerase activity. The other choices are incorrect because:
A: Inducer activates gene expression.
B: Repressor inhibits gene expression by binding to DNA.
D: Leader is not a term related to allosteric regulation.
Which nutrients aid in capillary synthesis and collagen production by the fibroblasts in wound healing?
- A. Fats
- B. Proteins
- C. Vitamin C
- D. Vitamin A
Correct Answer: C
Rationale: Vitamin C plays a crucial role in collagen synthesis, which is essential for wound healing. It supports the formation of new blood vessels (angiogenesis) and strengthens connective tissue.
What type of diseases does the immune system primarily defend against?
- A. Autoimmune diseases
- B. Infectious diseases
- C. Neurological disorders
- D. Cardiovascular diseases
Correct Answer: B
Rationale: The correct answer is B: Infectious diseases. The immune system's main function is to protect the body from foreign invaders such as bacteria, viruses, and parasites. It recognizes and eliminates these pathogens to prevent infections. Autoimmune diseases (A) occur when the immune system mistakenly attacks healthy cells. Neurological disorders (C) and cardiovascular diseases (D) are not primarily defended against by the immune system as they are not caused by external pathogens.
The rearrangement of gene segments that occurs randomly in B cell receptor genes and T cell receptor genes:
- A. Occurs during clonal expansion of B cells and T cells
- B. Involves rapid genetic mutation after lymphocytes become activated
- C. Allows the mature lymphocyte population to recognize an enormous diversity of antigens
- D. Occurs in the DNA of all cells in the body
Correct Answer: C
Rationale: Step 1: Gene rearrangement in B cell and T cell receptor genes creates unique receptor proteins.
Step 2: This diversity allows mature lymphocytes to recognize a wide range of antigens.
Step 3: This process is crucial for adaptive immune response and antigen specificity.
Step 4: Choices A and B do not accurately describe gene rearrangement.
Step 5: Choice D is incorrect as gene rearrangement is specific to lymphocytes, not all cells in the body.
All of the following are true about antibodies, EXCEPT which one?
- A. They fix complement.
- B. They occur on the surface of B-lymphocyte
- C. They predominate the primary immune response to antigen.
- D. have a single, defined amino acid sequence due to variability.
Correct Answer: D
Rationale: The correct answer is D because antibodies do not have a single, defined amino acid sequence due to variability in their structure. This variability is a result of somatic recombination and hypermutation.
A: Antibodies can fix complement, leading to the destruction of pathogens.
B: Antibodies are produced by B-lymphocytes and can occur on their surface as B-cell receptors.
C: Antibodies predominate the secondary immune response, not the primary response, as memory B-cells are generated during the primary response for a quicker and more robust secondary response.