Nokea
The membrane of gas vesicles is composed of:
- A. triglycerides
- B. phospholipids
- C. proteins
- D. lipopolysaccharide
Correct Answer: C
Rationale: The correct answer is C: proteins. Gas vesicles are gas-filled structures found in certain bacteria and archaea to provide buoyancy. The membrane of gas vesicles is predominantly composed of proteins that form a semi-permeable barrier to trap gas. Proteins are essential for the structure and function of gas vesicles. Triglycerides (A) are not typically found in membrane structures, phospholipids (B) are more common in cell membranes, and lipopolysaccharides (D) are typically found in the outer membrane of Gram-negative bacteria, not in gas vesicle membranes.
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What type of immunity is provided by T lymphocytes?
- A. Humoral immunity
- B. Cell-mediated immunity
- C. Passive immunity
- D. Innate immunity
Correct Answer: B
Rationale: The correct answer is B: Cell-mediated immunity. T lymphocytes are a type of white blood cell that plays a critical role in cell-mediated immunity by directly attacking infected cells and coordinating the immune response. This type of immunity is essential for fighting intracellular pathogens such as viruses and certain bacteria.
A: Humoral immunity is mediated by B cells and involves the production of antibodies to neutralize pathogens. T lymphocytes do not directly participate in humoral immunity.
C: Passive immunity is acquired through the transfer of antibodies from one individual to another, providing immediate protection. T lymphocytes are not involved in passive immunity.
D: Innate immunity is the body's first line of defense against pathogens and does not involve T lymphocytes, which are part of the adaptive immune response.
What defect in cellular proliferation is involved in the development of cancer?
- A. A rate of cell proliferation that is more rapid than that of normal body cells
- B. Shortened phases of cell life cycles with occasional skipping of G1 or S phases
- C. Rearrangement of stem cell RNA that causes abnormal cellular protein synthesis
- D. Indiscriminate and continuous proliferation of cells with loss of contact inhibition
Correct Answer: D
Rationale: Cancer involves indiscriminate and continuous proliferation of cells with loss of contact inhibition, which allows cells to grow uncontrollably.
What distinguishes NK cells from other lymphocytes?
- A. They are part of adaptive immunity
- B. They do not require prior antigen sensitization
- C. They directly produce antibodies
- D. They phagocytose pathogens
Correct Answer: B
Rationale: The correct answer is B because NK cells do not require prior antigen sensitization to recognize and attack infected cells. This distinguishes them from other lymphocytes, such as T and B cells, which are part of adaptive immunity and require prior exposure to specific antigens. NK cells are part of innate immunity and can directly recognize and kill infected or abnormal cells without prior activation. Choices A, C, and D are incorrect as NK cells are not part of adaptive immunity, do not directly produce antibodies, and do not phagocytose pathogens.
What is the primary mechanism by which innate immunity differentiates between self and non-self?
- A. Somatic recombination
- B. Recognition of PAMPs via PRRs
- C. Presentation of antigens by MHC molecules
- D. Production of antibodies
Correct Answer: B
Rationale: The correct answer is B: Recognition of PAMPs via PRRs. Innate immunity distinguishes self from non-self by recognizing Pathogen-Associated Molecular Patterns (PAMPs) via Pattern Recognition Receptors (PRRs). This recognition triggers an immediate response to eliminate potential threats. Choices A, C, and D are incorrect because somatic recombination is a process in adaptive immunity, MHC molecules present antigens for recognition by T cells in adaptive immunity, and antibody production is part of adaptive immunity involving B cells.
Which cells play a key role in linking innate and adaptive immunity?
- A. B cells
- B. Dendritic cells
- C. Eosinophils
- D. NK cells
Correct Answer: B
Rationale: The correct answer is B: Dendritic cells. Dendritic cells are antigen-presenting cells that bridge the innate and adaptive immune responses by capturing and presenting antigens to T cells, thus initiating the adaptive immune response. They are crucial for activating T cells and initiating specific immune responses.
A: B cells are responsible for antibody production in the adaptive immune response, not for linking innate and adaptive immunity.
C: Eosinophils are primarily involved in parasitic infections and allergic reactions, not in linking innate and adaptive immunity.
D: NK cells are part of the innate immune system and are involved in detecting and killing infected cells, but they do not directly link innate and adaptive immunity.