Nokea
Which of the following is not considered a virulence factor?
- A. Flagella
- B. Effector proteins manipulating host actin cytoskeleton
- C. Toxins
- D. Peptidoglycan
Correct Answer: D
Rationale: The correct answer is D: Peptidoglycan. Peptidoglycan is a structural component of bacterial cell walls and does not directly contribute to the pathogenicity or virulence of the bacterium. Flagella aid in motility and colonization, effector proteins manipulate host cells, and toxins damage host tissues, all of which are virulence factors. Peptidoglycan is essential for maintaining cell shape and integrity but does not directly enhance the ability of the bacteria to cause disease.
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The bacterial cytoplasmic membrane contains:
- A. ester-linked phospholipids, but no sterols
- B. ester-linked phospholipids and sterols
- C. ether-linked phospholipids, but no sterols
- D. ether-linked phospholipids, sulfolipids, and glycolipids
Correct Answer: A
Rationale: The correct answer is A because bacterial cytoplasmic membranes typically contain ester-linked phospholipids but no sterols. Ester-linked phospholipids are the main component of bacterial cell membranes, providing structure and function. Sterols, like cholesterol, are not commonly found in bacterial membranes. Choice B is incorrect because sterols are not present in bacterial membranes. Choice C is incorrect because ether-linked phospholipids are more commonly found in archaea, not bacteria. Choice D is incorrect because sulfolipids and glycolipids are not primary components of bacterial cytoplasmic membranes.
What are the effects of histamine released from mast cells?
- A. Increased vascular permeability and bronchoconstriction
- B. Neutralization of antigens and opsonization
- C. Complement activation and T cell proliferation
- D. Direct lysis of pathogens
Correct Answer: A
Rationale: The correct answer is A because histamine released from mast cells causes increased vascular permeability, leading to edema, and bronchoconstriction, contributing to respiratory symptoms. This is a key mechanism in allergic reactions.
B: Neutralization of antigens and opsonization are functions of antibodies, not histamine.
C: Complement activation and T cell proliferation are separate immune responses not mediated by histamine.
D: Direct lysis of pathogens is typically carried out by immune cells like macrophages and natural killer cells, not histamine.
The precursor of IL-1β is processed to its active form by
- A. Pro-caspase 1
- B. Caspase 1
- C. Procaspase 8
- D. Caspase 8
Correct Answer: B
Rationale: The correct answer is B: Caspase 1. Caspase 1 is responsible for the cleavage of pro-IL-1β into its active form IL-1β. This process involves the activation of Caspase 1 by various inflammasomes upon sensing danger signals. Pro-caspase 1 (Choice A) is the inactive precursor form of Caspase 1 and is not involved in processing IL-1β. Procaspase 8 (Choice C) and Caspase 8 (Choice D) are part of the extrinsic apoptosis pathway and are not directly involved in the processing of IL-1β. Therefore, the correct choice is Caspase 1 as it specifically cleaves pro-IL-1β to its active form.
The process of somatic hypermutation:
- A. Can lead to the formation of antibodies with higher affinity for the antigen
- B. Occurs mainly in the CDR regions of immunoglobulin heavy and light chain genes
- C. Occurs in germinal centres
- D. All of the above are correct
Correct Answer: D
Rationale: The correct answer is D because somatic hypermutation can lead to the formation of antibodies with higher affinity for the antigen by introducing point mutations in the variable regions of immunoglobulin genes. This process mainly occurs in the complementarity-determining regions (CDRs) of immunoglobulin heavy and light chain genes, which are critical for antigen binding. Somatic hypermutation takes place in the germinal centers of secondary lymphoid organs, where B cells undergo rapid proliferation and selection based on antigen binding affinity. Therefore, all the statements in choices A, B, and C are correct, making option D the right answer.
Which historical event provides evidence for immune adaptation?
- A. Spanish flu pandemic
- B. The Black Death caused by Yersinia pestis
- C. HIV/AIDS epidemic
- D. The eradication of smallpox
Correct Answer: B
Rationale: The Black Death caused by Yersinia pestis is the correct answer because it led to immune adaptation in survivors. Yersinia pestis triggered the body to develop immunity. The Spanish flu pandemic, HIV/AIDS epidemic, and eradication of smallpox did not directly result in immune adaptation like the Black Death. The Spanish flu and HIV/AIDS were caused by viruses that did not lead to long-term immunity, and smallpox eradication was achieved through vaccinations, not natural immune adaptation.