Nokea
Which of the following bacteria can produce endotoxins that cause septic shock?
- A. Escherichia coli
- B. Salmonella enterica
- C. Pseudomonas aeruginosa
- D. All of the above
Correct Answer: D
Rationale: The correct answer is D because all of the mentioned bacteria (Escherichia coli, Salmonella enterica, and Pseudomonas aeruginosa) are gram-negative bacteria that produce endotoxins in their cell walls. Endotoxins are released when the bacteria are destroyed, leading to the activation of the immune system and potentially causing septic shock. Escherichia coli and Salmonella enterica are common causes of gastrointestinal infections, while Pseudomonas aeruginosa is known for causing infections in immunocompromised individuals. Therefore, all three bacteria can produce endotoxins that contribute to septic shock. Choices A, B, and C are incorrect because each of these bacteria individually can produce endotoxins that lead to septic shock.
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Unlike eukaryotic cytoplasm, the prokaryotic one is:
- A. More complex
- B. Simpler
- C. There is no difference in the structure
- D. None of the above
Correct Answer: B
Rationale: The correct answer is B: Simpler. Prokaryotic cytoplasm is simpler than eukaryotic cytoplasm because prokaryotic cells lack membrane-bound organelles such as a nucleus, mitochondria, and endoplasmic reticulum that are present in eukaryotic cells. Prokaryotic cytoplasm contains fewer components and structures compared to eukaryotic cytoplasm, making it less complex. Therefore, the prokaryotic cytoplasm is simpler in structure. Choices A, C, and D are incorrect because prokaryotic cytoplasm is not more complex than eukaryotic cytoplasm, there is a clear difference in structure between prokaryotic and eukaryotic cytoplasm, and the statement "None of the above" is not accurate as the correct answer is B.
Which of the following bacteria is responsible for causing cholera?
- A. Shigella dysenteriae
- B. Vibrio cholerae
- C. Salmonella enterica
- D. Escherichia coli
Correct Answer: B
Rationale: The correct answer is B: Vibrio cholerae. Cholera is caused by Vibrio cholerae, a bacterium that infects the small intestine, leading to severe diarrhea and dehydration. This bacterium produces a toxin that causes the symptoms of cholera.
A: Shigella dysenteriae causes dysentery, not cholera.
C: Salmonella enterica causes food poisoning, not cholera.
D: Escherichia coli can cause food poisoning but not cholera.
Microscopy of sputum from a tuberculosis patient revealed acid-fast rods stained red using the Ziehl-Neelsen method. What structural feature allows this staining?
- A. Mycolic acid in the cell wall
- B. Capsule surrounding the cell
- C. Flagella on the cell surface
- D. Thick peptidoglycan layer
Correct Answer: A
Rationale: The correct answer is A: Mycolic acid in the cell wall. Mycolic acid is a unique component of the cell wall of Mycobacterium species, including the causative agent of tuberculosis. The Ziehl-Neelsen method uses acid-fast staining, where mycolic acid confers resistance to decolorization by acid-alcohol, causing the bacteria to retain the red stain. Choices B, C, and D are incorrect as capsules, flagella, and peptidoglycan layers do not directly contribute to acid-fast staining characteristic of Mycobacterium species.
Salmonellosis is caused by:
- A. Salmonella typhi
- B. Salmonella enteritidis
- C. Shigella flexneri
- D. None of the above
Correct Answer: B
Rationale: The correct answer is B: Salmonella enteritidis. Salmonellosis is typically caused by Salmonella species, with Salmonella enteritidis being one of the common culprits. Salmonella typhi causes typhoid fever, not salmonellosis. Shigella flexneri is responsible for causing shigellosis, a different bacterial infection. Choosing "None of the above" is incorrect as Salmonella enteritidis is a known cause of salmonellosis.
What is the structure of bacterial flagella?
- A. 9+2 microtubule arrangement
- B. protein filaments made of flagellin
- C. lipid bilayer
- D. peptidoglycan layer
Correct Answer: B
Rationale: The correct answer is B: protein filaments made of flagellin. Bacterial flagella are composed of flagellin proteins arranged in helical filaments. This structure allows for movement and propulsion of bacteria.
A: 9+2 microtubule arrangement is incorrect because this structure is typically found in eukaryotic flagella, not bacterial flagella.
C: Lipid bilayer is incorrect as it is a structural component of cell membranes, not bacterial flagella.
D: Peptidoglycan layer is incorrect as it is a component of bacterial cell walls, not flagella.