Nokea
The prokaryotic cell does not possess:
- A. Ribosomes
- B. Endoplasmic reticulum
- C. Chromosome
- D. Peptidoglycan
Correct Answer: B
Rationale: The correct answer is B: Endoplasmic reticulum. Prokaryotic cells lack membrane-bound organelles like the endoplasmic reticulum, which is present in eukaryotic cells. Prokaryotes do possess ribosomes for protein synthesis (A), a chromosome (C) for genetic material, and peptidoglycan (D) in their cell walls. The absence of endoplasmic reticulum is a key characteristic that distinguishes prokaryotic cells from eukaryotic cells.
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Which bacteria is known for causing a disease characterized by a pseudomembrane in the throat?
- A. Clostridium tetani
- B. Bordetella pertussis
- C. Corynebacterium diphtheriae
- D. Streptococcus pyogenes
Correct Answer: C
Rationale: The correct answer is C: Corynebacterium diphtheriae. This bacterium causes diphtheria, a disease characterized by a pseudomembrane in the throat. This pseudomembrane is a result of the bacterial exotoxins causing inflammation and necrosis of the throat tissues. Clostridium tetani (A) causes tetanus, characterized by muscle stiffness, not a pseudomembrane in the throat. Bordetella pertussis (B) causes whooping cough, with symptoms of severe coughing fits but no pseudomembrane. Streptococcus pyogenes (D) causes strep throat, but does not produce a pseudomembrane.
Which bacteria are most commonly associated with food poisoning?
- A. Clostridium botulinum
- B. Salmonella enterica
- C. Escherichia coli
- D. All of the above
Correct Answer: D
Rationale: The correct answer is D: All of the above. Clostridium botulinum, Salmonella enterica, and Escherichia coli are all common bacteria associated with food poisoning. Clostridium botulinum produces a potent neurotoxin causing botulism. Salmonella enterica causes salmonellosis, a common foodborne illness. Escherichia coli can produce toxins leading to food poisoning. Therefore, since all three bacteria are known to cause food poisoning, the correct answer is D. Choices A, B, and C are incorrect because each of these bacteria individually is commonly associated with food poisoning, not just one of them.
Which of the following pathogens can cause meningitis?
- A. Staph. aureus
- B. Strep. pyogenes
- C. Strep. pneumoniae
- D. None of the above
Correct Answer: C
Rationale: Rationale for choice C (Strep. pneumoniae):
1. Strep. pneumoniae is a common cause of bacterial meningitis.
2. It is a leading pathogen responsible for meningitis in adults and children.
3. It can invade the bloodstream and reach the meninges, causing inflammation.
4. Treatment guidelines often include antibiotics effective against Strep. pneumoniae.
Summary of why other choices are incorrect:
A. Staph. aureus is not a common cause of meningitis.
B. Strep. pyogenes typically causes streptococcal infections but not meningitis.
D. "None of the above" is incorrect as Strep. pneumoniae can cause meningitis.
The term “zone of inhibition†is used in which of the following procedures?
- A. Use-dilution test
- B. Growth inhibition test
- C. Disk-diffusion test
- D. Multiple inhibition test
Correct Answer: C
Rationale: The correct answer is C: Disk-diffusion test. In the disk-diffusion test, the zone of inhibition refers to the area around an antimicrobial disk where bacterial growth is inhibited. This test is used to determine the susceptibility of bacteria to specific antibiotics. The other choices, such as A: Use-dilution test, B: Growth inhibition test, and D: Multiple inhibition test, do not specifically involve measuring the zone of inhibition and are not commonly used methods for testing antibiotic susceptibility.
Microscopic examination of dental plaque revealed unicellular organisms with two layers in their cytoplasm and wide pseudopodia. What is the likely causative agent?
- A. Entamoeba gingivalis
- B. Entamoeba histolytica
- C. Trichomonas tenax
- D. Lamblia intestinalis
Correct Answer: A
Rationale: Rationale:
1. Unicellular organisms with two layers in cytoplasm = Entamoeba gingivalis.
2. Wide pseudopodia = characteristic of Entamoeba genus.
3. Entamoeba histolytica causes amoebic dysentery, not dental plaque.
4. Trichomonas tenax causes periodontal disease, not dental plaque.
5. Lamblia intestinalis causes giardiasis, not related to dental plaque.