Nokea
Mucins are
- A. Produced by all epithelial cells
- B. Heavily glycosylated proteins that form a gel-like physical barrier on mucosal surfaces
- C. Natural antibiotics produced by specialized epithelial cells
- D. Found exclusively in the respiratory tract
Correct Answer: B
Rationale: Step-by-step rationale:
1. Mucins are heavily glycosylated proteins that form a gel-like barrier on mucosal surfaces.
2. This barrier helps protect the underlying tissues from pathogens and physical damage.
3. Mucins are primarily produced by goblet cells in epithelial tissues.
4. Choice B correctly describes the function and structure of mucins.
Summary:
- Choice A is incorrect because not all epithelial cells produce mucins.
- Choice C is incorrect as mucins are not natural antibiotics.
- Choice D is incorrect as mucins are present in various mucosal surfaces, not exclusively in the respiratory tract.
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Dendritic cells play a role in:
- A. Costimulation of naïve T cells
- B. Processing of protein antigens to generate peptides
- C. Presentation of peptide-MHC complexes for recognition by T cell receptors
- D. All of the above
Correct Answer: D
Rationale: Dendritic cells play a crucial role in the immune system. Firstly, they provide costimulation to activate naïve T cells (A). Secondly, they process protein antigens into peptides for antigen presentation (B). Finally, dendritic cells present peptide-MHC complexes to T cell receptors for immune response activation (C). Therefore, the correct answer is D, as dendritic cells are involved in all these processes essential for initiating and regulating immune responses. Choices A, B, and C are incorrect as they are individual roles of dendritic cells and do not encompass the full range of functions that dendritic cells perform.
The nurse is performing morning care for a patient who sustained a fractured pelvis and bilateral femur fractures yesterday in a motorcycle collision. The patient complains of shortness of breath. Assessment reveals audible wheezes and oxygen saturation of 76%. What action should the nurse take first?
- A. Establish a peripheral intravenous (IV) line.
- B. Inform the charge nurse.
- C. Explain the patient's change in status to his family.
- D. Raise patient to high Fowler position.
Correct Answer: D
Rationale: Step 1: The patient complains of shortness of breath and has audible wheezes, indicating potential respiratory distress.
Step 2: Oxygen saturation of 76% is critically low and requires immediate intervention.
Step 3: Raising the patient to a high Fowler position helps improve lung expansion and oxygenation.
Step 4: This action takes priority to improve the patient's breathing and oxygen saturation levels.
Summary: A is incorrect as establishing an IV line is not the immediate priority. B is incorrect as informing the charge nurse delays direct patient care. C is incorrect as addressing the family is secondary to addressing the patient's urgent needs.
Which of the following enzymes removes 5' phosphate groups thereby preventing or decreasing the self-sealing of restricted plasmid vector molecules?
- A. Calf intestinal phosphatase
- B. Pyrophosphatase
- C. Phosphohydrolase
- D. phosphate exonuclease
Correct Answer: A
Rationale: The correct answer is A: Calf intestinal phosphatase. This enzyme removes 5' phosphate groups from DNA molecules, preventing self-ligation of restricted plasmid vectors. This step is crucial in generating linearized vectors for downstream applications. Pyrophosphatase (B) hydrolyzes pyrophosphate bonds, not 5' phosphate groups. Phosphohydrolase (C) is a general term for enzymes that hydrolyze phosphoester bonds, not specific to 5' phosphate removal. Phosphate exonuclease (D) degrades nucleic acids by removing nucleotides from the 3' end, not the 5' phosphate group.
What distinguishes Type V hypersensitivity from Type II?
- A. It is mediated by T cells
- B. Antibodies stimulate receptors instead of destroying them
- C. It involves immune complex formation
- D. It does not involve the immune system
Correct Answer: B
Rationale: The correct answer is B because Type V hypersensitivity involves antibodies stimulating receptors instead of destroying them. In Type II hypersensitivity, antibodies target antigens on cell surfaces, leading to cell destruction. In Type V, antibodies bind to cell receptors, causing abnormal receptor activation. Choices A, C, and D are incorrect because Type V hypersensitivity is not mediated by T cells (A), does not involve immune complex formation (C), and does involve the immune system (D). Therefore, the unique characteristic of Type V hypersensitivity is the stimulation of receptors by antibodies, making choice B the correct answer.
Identify the option that represents the correct order of events in naïve T cell activation:
- A. Entry into the site of infection, antigen recognition, clonal expansion
- B. Antigen recognition, clonal expansion, entry into the site of infection
- C. Entry into the site of infection, clonal expansion, antigen recognition
- D. Antigen recognition, entry into the site of infection, clonal expansion
Correct Answer: B
Rationale: The correct order of events in naïve T cell activation is: antigen recognition, clonal expansion, entry into the site of infection. First, T cells must recognize the specific antigen presented by antigen-presenting cells. This recognition triggers clonal expansion, where T cells proliferate and differentiate into effector cells. Finally, the activated T cells migrate to the site of infection to combat the pathogen. Option B is correct because it follows this sequential order. Options A, C, and D are incorrect because they do not adhere to the correct sequence of events in naïve T cell activation.