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Which of the following best describes the function of bacterial capsules?
- A. Enhance bacterial motility
- B. Enable bacterial adherence to surfaces
- C. Prevent bacterial DNA replication
- D. Protect bacteria from desiccation
Correct Answer: B
Rationale: The correct answer is B: Enable bacterial adherence to surfaces. Bacterial capsules are a protective layer outside the cell wall that helps bacteria adhere to surfaces and evade host immune responses. This allows bacteria to colonize and infect host tissues.
A: Enhancing bacterial motility is typically associated with flagella, not capsules.
C: Bacterial DNA replication is not directly affected by capsules.
D: Bacterial capsules do play a role in protecting bacteria from desiccation by providing a barrier against drying out. However, the primary function is enabling adherence to surfaces.
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Which of the following statements is not correct with regard to Mycobacterium tuberculosis and/or the disease it caused?
- A. The pathogen contains mycolic acid in the cell wall
- B. The pathogen can live intracellularly in macrophages
- C. The antibodies formed are protective
- D. None of the above
Correct Answer: C
Rationale: Rationale:
C is the correct answer because antibodies formed against Mycobacterium tuberculosis are not protective. They do not efficiently clear the infection due to the bacterium's ability to evade the immune response by residing intracellularly in macrophages. Antibodies play a minimal role in controlling tuberculosis compared to cell-mediated immunity.
Summary:
A is incorrect because Mycobacterium tuberculosis does contain mycolic acid in its cell wall. B is incorrect because the pathogen can indeed live intracellularly in macrophages. D is incorrect as C is the correct answer.
Which description matches most to adenoviruses:
- A. Middle sized, naked icosahedral capsid, double-stranded DNA
- B. Small-sized, enveloped capsid, ssRNA
- C. Large, enveloped capsid, double stranded DNA
- D. None of the above
Correct Answer: A
Rationale: Step-by-step rationale:
1. Adenoviruses are DNA viruses, so choices B and C (ssRNA and DNA) are incorrect.
2. Adenoviruses have a middle-sized, naked icosahedral capsid, making choice A the correct description.
3. Choice D is incorrect as adenoviruses do have specific characteristics, making "None of the above" an inaccurate option.
In summary, the correct answer A is supported by the fact that adenoviruses have a middle-sized, naked icosahedral capsid and contain double-stranded DNA. Choices B, C, and D are incorrect as they do not align with the characteristics of adenoviruses.
Which is the most abundant immunoglobin in a normal healthy adult
- A. IgG
- B. IgA
- C. IgE
- D. IgD
Correct Answer: A
Rationale: Step-by-step rationale:
1. IgG is the most abundant immunoglobin in a normal healthy adult due to its long half-life and diverse functions.
2. It plays a crucial role in immune response by neutralizing pathogens and enhancing phagocytosis.
3. IgA is mainly found in mucosal areas, IgE is involved in allergic reactions, and IgD's function is not fully understood.
4. Therefore, IgG is the correct answer as it is the predominant immunoglobin in circulation, providing broad immune protection.
For the structure of rubella virus, it is true that
- A. has icosahedral type of symmetry
- B. is ssDNA virus
- C. does not have an envelope
- D. does not have glycoprotein spikes
Correct Answer: A
Rationale: Step 1: Rubella virus belongs to the Togaviridae family, which typically exhibits icosahedral symmetry.
Step 2: Icosahedral symmetry refers to a structure with 20 equilateral triangular faces, which is characteristic of many viruses, including rubella.
Step 3: Therefore, choice A is correct as rubella virus indeed has icosahedral type of symmetry.
Summary:
- Choice B is incorrect as rubella virus is an ssRNA virus, not ssDNA.
- Choice C is incorrect as rubella virus does have an envelope derived from the host cell membrane.
- Choice D is incorrect as rubella virus does have glycoprotein spikes on its surface.
Which bacteria is responsible for causing cholera?
- A. Shigella dysenteriae
- B. Vibrio cholerae
- C. Salmonella enterica
- D. Clostridium perfringens
Correct Answer: B
Rationale: The correct answer is B: Vibrio cholerae. Cholera is caused by this specific bacterium due to its production of cholera toxin, leading to severe watery diarrhea. Shigella dysenteriae causes dysentery, Salmonella enterica causes salmonellosis, and Clostridium perfringens causes food poisoning, none of which present with the characteristic symptoms of cholera.