Nokea
Which of the following statements for genus Klebsiella is correct?
- A. They have real capsule and are non-motile
- B. They are obligatory anaerobic
- C. They form spores only under aerobic conditions
- D. None of the above
Correct Answer: A
Rationale: The correct answer is A because Klebsiella species have a real capsule, which is a distinguishing feature used for their identification. This capsule helps them evade the host immune response. Additionally, Klebsiella species are non-motile, meaning they do not possess flagella for movement. Choices B and C are incorrect because Klebsiella species are facultative anaerobes and do not form spores under any conditions. Choice D is also incorrect as option A is the correct statement for genus Klebsiella.
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The process by which the nucleus of protozoans undergoes multiple divisions before the cell divides is called:
- A. budding
- B. mitosis
- C. schizogony
- D. fragmentation
Correct Answer: C
Rationale: Rationale: Schizogony is the process in protozoans where multiple nuclear divisions occur before cell division. This results in the formation of multiple daughter cells.
- A: Budding is a form of asexual reproduction where a new organism grows from an outgrowth on the parent.
- B: Mitosis is a type of cell division that results in two identical daughter cells.
- D: Fragmentation is a form of asexual reproduction where an organism breaks into fragments, each developing into a new organism.
Chitin is a component of the cell wall of:
- A. fungi
- B. bacteria
- C. viruses
- D. viruses
Correct Answer: C
Rationale: Chitin is a polysaccharide found in the cell walls of fungi. Bacteria have cell walls made of peptidoglycan, not chitin. Viruses do not have cell walls as they are acellular entities. Therefore, the correct answer is A: fungi.
A bacteriophage is a(n) ____________ virus.
- A. helical
- B. icosahedral
- C. enveloped
- D. complex
Correct Answer: D
Rationale: The correct answer is D: complex. Bacteriophages are considered complex viruses because they have a complex structure consisting of a polyhedral head, a helical tail, and tail fibers. The head contains the viral genetic material, while the tail facilitates attachment to the host bacterial cell. This complexity distinguishes bacteriophages from simpler viruses like helical and icosahedral viruses. Helical viruses have a rod-like shape, while icosahedral viruses have a symmetrical, 20-sided structure. Enveloped viruses have a lipid bilayer envelope surrounding their capsid, which bacteriophages lack. Therefore, the unique and intricate structure of bacteriophages classifies them as complex viruses.
Which of the following best describes a Gram-negative bacterium?
- A. Has a thick peptidoglycan layer
- B. Has an outer membrane with lipopolysaccharides
- C. Stains purple
- D. Has no cell wall
Correct Answer: B
Rationale: The correct answer is B because Gram-negative bacteria have an outer membrane with lipopolysaccharides, which is a key characteristic used in Gram staining. This outer membrane is responsible for the pink/red color seen when stained with Gram stain. Choice A is incorrect because Gram-negative bacteria have a thin peptidoglycan layer. Choice C is incorrect because Gram-negative bacteria stain pink, not purple. Choice D is incorrect because all bacteria have a cell wall, but Gram-negative bacteria have a different structure compared to Gram-positive bacteria.
The cell envelope in gram positive bacteria is:
- A. Two-layer
- B. Three-layer
- C. One-layer
- D. There is no a cell envelope in gram-positive bacteria
Correct Answer: A
Rationale: The correct answer is A: Two-layer. In gram-positive bacteria, the cell envelope consists of two layers: the thick peptidoglycan layer and the cytoplasmic membrane. The peptidoglycan layer is much thicker compared to gram-negative bacteria, providing structural support and protection. The cytoplasmic membrane is located beneath the peptidoglycan layer and serves as a barrier between the cytoplasm and the external environment. The other choices are incorrect because gram-positive bacteria do have a cell envelope, it is composed of two layers, not three layers, and it is not just a single layer. Choice D is incorrect as it states that there is no cell envelope in gram-positive bacteria, which is not true.