Nokea
Which of the following are not found in Cyanobacteria?
- A. thylakoids
- B. gas vesicles
- C. chloroplasts
- D. heterocysts
Correct Answer: C
Rationale: The correct answer is C: chloroplasts. Cyanobacteria do not have chloroplasts because they are prokaryotic organisms and do not possess membrane-bound organelles like chloroplasts found in eukaryotic cells. Instead, they perform photosynthesis using thylakoids, which are membrane-bound compartments where photosynthesis occurs. Gas vesicles are also present in cyanobacteria and help regulate their buoyancy. Heterocysts are specialized cells that aid in nitrogen fixation, a process that allows cyanobacteria to convert atmospheric nitrogen into a form that can be used by the organism. Therefore, the absence of chloroplasts in cyanobacteria makes choice C the correct answer.
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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 of the following molecular interactions mediate signal 2 during activation of naïve T cells
- A. L-Selectin/PNAD
- B. CD4/MHC II or CD8/MHC I
- C. TCR/MHC I or TCR/MHC II
- D. TCR/CD3
Correct Answer: E
Rationale: I'm sorry, but there seems to be a mistake in the question as the correct answer is not listed among the choices provided. Please provide the correct options or the correct answer so I can give you the detailed explanation you are looking for.
Lymphokines are protein substances produced in small amounts by lymphocytes and move from cell to cell carrying message through the immune system. The most common lymphokine is:
- A. Vaccine
- B. Antigen
- C. Antibody
- D. Interferon
Correct Answer: D
Rationale: Rationale for Correct Answer (D - Interferon):
1. Lymphokines are protein substances produced by lymphocytes.
2. Interferon is a type of lymphokine produced by lymphocytes during viral infections.
3. It helps in regulating the immune response and inhibiting viral replication.
4. Interferon moves from cell to cell carrying messages through the immune system.
Summary of Incorrect Choices:
A: Vaccine - Not a lymphokine, but a substance used to stimulate the immune system.
B: Antigen - Not a lymphokine, but a substance that triggers an immune response.
C: Antibody - Not a lymphokine, but a protein produced by the immune system to neutralize pathogens.
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.
When a patient is undergoing brachytherapy, what is it important for the nurse to be aware of when caring for this patient?
- A. The patient will undergo simulation to identify and mark the field of treatment
- B. The patient is a source of radiation and personnel must wear film badges during care
- C. The goal of this treatment is only palliative and the patient should be aware of the expected outcome
- D. Computerized dosimetry is used to determine the maximum dose of radiation to the tumor within an acceptable dose to normal tissue
Correct Answer: B
Rationale: Patients undergoing brachytherapy emit radiation, requiring safety measures for healthcare providers.