Nokea
The main function of bacterial ribosomes is:
- A. DNA replication
- B. protein synthesis
- C. cell wall synthesis
- D. RNA splicing
Correct Answer: B
Rationale: The correct answer is B: protein synthesis. Bacterial ribosomes are responsible for translating messenger RNA into proteins through a process called translation. Ribosomes are composed of both protein and RNA molecules and facilitate the binding of transfer RNA to the messenger RNA to assemble the amino acids in the correct order to form a protein. DNA replication (A) is carried out by enzymes such as DNA polymerase, not ribosomes. Cell wall synthesis (C) is a process involving enzymes that build the structure of the cell wall in bacteria. RNA splicing (D) is a eukaryotic process that involves removing introns from pre-mRNA molecules, which is not a function of bacterial ribosomes.
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Pseudomonas aeruginosa can cause:
- A. Burn wounds infection, severe pneumonia in patients with cystic fibrosis, nosocomial infections
- B. Food poisoning
- C. Bacterial pharyngitis
- D. None of the above
Correct Answer: A
Rationale: Step-by-step rationale for answer A:
1. Pseudomonas aeruginosa is known to cause burn wounds infections due to its ability to survive in moist environments.
2. It can cause severe pneumonia in patients with cystic fibrosis due to its resistance to antibiotics and ability to form biofilms.
3. It is a common cause of nosocomial infections in hospitals due to its ability to colonize medical equipment and surfaces.
Summary of other choices:
B. Pseudomonas aeruginosa typically does not cause food poisoning, as it is not a common pathogen associated with foodborne illnesses.
C. Bacterial pharyngitis is usually caused by Streptococcus pyogenes, not Pseudomonas aeruginosa, making this choice incorrect.
D. None of the above is incorrect as Pseudomonas aeruginosa is associated with specific infections mentioned in option A.
Which of the following diseases is transmitted by the fecal–oral route?
- A. Ehrlichiosis
- B. Peptic ulcer
- C. Lyme disease
- D. Tularemia
Correct Answer: B
Rationale: The correct answer is B: Peptic ulcer. Peptic ulcers are commonly caused by Helicobacter pylori bacteria, which can be transmitted through the fecal-oral route. This means that the bacteria from infected feces can be ingested through contaminated food or water, leading to the development of peptic ulcers in the gastrointestinal tract.
Incorrect choices:
A: Ehrlichiosis - Ehrlichiosis is a tick-borne disease transmitted through the bite of an infected tick, not through the fecal-oral route.
C: Lyme disease - Lyme disease is also transmitted through the bite of an infected tick, specifically the black-legged tick.
D: Tularemia - Tularemia is a bacterial disease typically transmitted through insect bites, handling of infected animals, or ingestion of contaminated water, not through the fecal-oral route.
Algae that contain agar in their cell walls belong to:
- A. Chrysophyta
- B. Rhodophyta
- C. Chlorophyta
- D. Phaeophyta
Correct Answer: B
Rationale: The correct answer is B: Rhodophyta. Rhodophyta is the phylum of red algae, which are known to contain agar in their cell walls. Agar is a gelatinous substance derived from these algae. Chrysophyta (A), Chlorophyta (C), and Phaeophyta (D) do not typically contain agar in their cell walls. Chrysophyta includes diatoms, Chlorophyta includes green algae, and Phaeophyta includes brown algae, none of which are known for agar production. Therefore, Rhodophyta is the correct choice based on the presence of agar in their cell walls.
Which of the following bacteria causes the disease diphtheria?
- A. Bordetella pertussis
- B. Corynebacterium diphtheriae
- C. Streptococcus pyogenes
- D. Neisseria meningitidis
Correct Answer: B
Rationale: The correct answer is B: Corynebacterium diphtheriae. This bacterium produces a toxin that causes diphtheria by inhibiting protein synthesis, leading to the formation of a pseudomembrane in the throat. Bordetella pertussis causes whooping cough, Streptococcus pyogenes causes strep throat, and Neisseria meningitidis causes meningitis. Corynebacterium diphtheriae is the only bacterium among the choices known to cause diphtheria due to its specific toxin production.
A patient with a sore throat had a throat smear stained by Neisser's method. Microscopy revealed rods with polar dark blue granules. What microorganism is likely responsible?
- A. Corynebacterium diphtheriae
- B. Bacillus anthracis
- C. Clostridium tetani
- D. Escherichia coli
Correct Answer: A
Rationale: The presence of rods with polar dark blue granules stained by Neisser's method indicates metachromatic granules consistent with Corynebacterium diphtheriae. The characteristic staining pattern is due to the presence of polar granules in the bacterial cells, a feature specific to Corynebacterium diphtheriae. Bacillus anthracis, Clostridium tetani, and Escherichia coli do not exhibit this staining pattern or morphology typical of Corynebacterium diphtheriae, making them incorrect choices.