Nokea
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.
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Which of the following statements is true?
- A. MHC class I and MHC class II molecules both consist of two transmembrane protein chains
- B. MHC class I molecules have one peptide-binding site whereas MHC class II molecules have two peptide-binding sites
- C. A given MHC molecule binds only one peptide at a time
- D. MHC molecules on the cell surface have empty peptide-binding sites in the absence of infection
Correct Answer: C
Rationale: The correct answer is C because a given MHC molecule can bind only one peptide at a time. This is essential for the proper presentation of antigens to immune cells. MHC class I and class II molecules do not consist of two transmembrane protein chains (A), MHC class I molecules have one peptide-binding site while MHC class II molecules have one peptide-binding site (B), and MHC molecules on the cell surface typically have peptides bound to their peptide-binding sites, even in the absence of infection (D).
Priority Decision: During care of patients, what is the most important precaution for preventing transmission of infections?
- A. Wearing face and eye protection during routine daily care of the patient
- B. Wearing nonsterile gloves when in contact with body fluids, excretions, and contaminated items
- C. Wearing a gown to protect the skin and clothing during patient care activities likely to soil clothing
- D. Hand washing after touching fluids and secretions and removing gloves, as well as between patient contacts
Correct Answer: D
Rationale: Hand hygiene remains the single most effective measure in preventing the spread of infections, even when personal protective equipment (PPE) is used.
What is characteristic of chronic inflammation?
- A. It may last 2 to 3 weeks.
- B. The injurious agent persists or repeatedly injures tissue.
- C. Infective endocarditis is an example of chronic inflammation.
- D. Neutrophils are the predominant cell type at the site of inflammation.
Correct Answer: B
Rationale: Chronic inflammation occurs when the cause of the initial injury persists or recurs, leading to ongoing tissue damage and repair. Unlike acute inflammation, it involves lymphocytes and macrophages rather than neutrophils.
Which of the following are not examples of a terminal electron acceptor in anaerobic respiration?
- A. nitrate
- B. hydrogen sulfate
- C. iron hydroxide
- D. Hâ‚‚
Correct Answer: D
Rationale: The correct answer is D: H₂. In anaerobic respiration, H₂ can act as a terminal electron acceptor, so it is not an incorrect example. Nitrate, hydrogen sulfate, and iron hydroxide are all examples of terminal electron acceptors in anaerobic respiration. H₂ is commonly used in microbial processes as an electron donor, not as a terminal electron acceptor. This is because H₂ is typically oxidized to produce energy, rather than accepting electrons.
The intestinal epithelial cells that specialize in the production of antimicrobial peptides are called:
- A. Goblet cells
- B. Enterocytes
- C. Paneth cells
- D. Epithelial stem cells
Correct Answer: C
Rationale: The correct answer is C: Paneth cells. Paneth cells are specialized intestinal epithelial cells located in the small intestine that produce antimicrobial peptides to help defend against pathogens. They play a crucial role in maintaining gut homeostasis. Goblet cells (A) secrete mucus, enterocytes (B) absorb nutrients, and epithelial stem cells (D) are responsible for cell regeneration, but they do not produce antimicrobial peptides like Paneth cells do.