Nokea
Infectious agents of various ultrastructures can be etiological agents of infectious diseases. Which of the groups named below HAS NO cellular structure, protein synthesizing, enzyme and energy systems?
- A. Viruses
- B. Fungi
- C. Bacteria
- D. Protozoa
Correct Answer: A
Rationale: The correct answer is A: Viruses. Viruses are acellular, meaning they lack cellular structure, protein synthesizing ability, enzymes, and energy systems. They are essentially genetic material (DNA or RNA) enclosed in a protein coat. Fungi (B), bacteria (C), and protozoa (D) are all cellular organisms with protein synthesizing, enzyme, and energy systems. Viruses rely on host cells to replicate and carry out metabolic functions, making them distinct from other groups.
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Which of the following proteins are encoded by herpesviruses and required for viral DNA replication?
- A. viral DNA polymerase
- B. ribonucleotide reductase
- C. neuraminidase
- D. thymidine kinase
Correct Answer: A
Rationale: The correct answer is A: viral DNA polymerase. This enzyme is essential for replicating the viral DNA during the herpesvirus life cycle. It catalyzes the synthesis of new DNA strands using the viral genomic template. Ribonucleotide reductase (B) is involved in nucleotide synthesis, but not directly in DNA replication. Neuraminidase (C) is an enzyme found in influenza viruses, not herpesviruses. Thymidine kinase (D) is an enzyme that phosphorylates thymidine, but its role is more related to nucleotide metabolism rather than viral DNA replication.
Antibiotics are distributed into following groups:
- A. Blockaders of protein synthesis
- B. Blockaders of cell wall synthesis
- C. Alternators of bacterial cytoplasm
- D. Nothing from above
Correct Answer: A
Rationale: The correct answer is A: Blockaders of protein synthesis because antibiotics in this group target bacterial ribosomes, preventing protein synthesis. This disrupts bacterial growth and replication. Choice B is incorrect as cell wall synthesis inhibitors target a different bacterial component. Choice C is incorrect as antibiotics do not alter bacterial cytoplasm. Choice D is incorrect as antibiotics do fall into different categories based on their mechanism of action.
Which of the following bacteria is capable of forming spores to survive in extreme conditions?
- A. Staphylococcus aureus
- B. Clostridium botulinum
- C. Escherichia coli
- D. Neisseria gonorrhoeae
Correct Answer: B
Rationale: The correct answer is B: Clostridium botulinum. This bacterium is capable of forming spores as a survival mechanism in harsh conditions. Spore formation allows it to remain dormant until conditions become favorable for growth again. Staphylococcus aureus (A), Escherichia coli (C), and Neisseria gonorrhoeae (D) do not form spores and rely on other mechanisms for survival. Staphylococcus aureus is a common skin bacterium, Escherichia coli is a gut bacterium, and Neisseria gonorrhoeae is a sexually transmitted bacterium.
A patient suffering form tuberculosis was treated with rifampicin, which caused drug resistance of tuberculosis mycobacteria. In order to reduce mycobacteria resistance, rifampicin should be combined with the following drug:
- A. Isoniazid
- B. Acyclovir
- C. Intraconazole
- D. Metronidazole
Correct Answer: A
Rationale: The correct answer is A: Isoniazid. When rifampicin is used alone, there is a risk of developing resistance. Isoniazid is commonly used in combination with rifampicin to prevent resistance by targeting different mechanisms in the bacteria. Isoniazid works by inhibiting mycolic acid synthesis, while rifampicin targets RNA polymerase. This combination therapy is known as the first-line treatment for tuberculosis. Choices B, C, and D are incorrect because they do not have the same mechanism of action as isoniazid and would not be effective in preventing rifampicin resistance.
The human pinworm Enterobius vermicularis lives in the __________ of humans.
- A. duodenum
- B. ileum
- C. transverse colon
- D. rectum
Correct Answer: D
Rationale: The correct answer is D: rectum. Pinworms typically inhabit the rectum area in humans, where they lay their eggs. This is because the female pinworm migrates to the rectum at night to deposit her eggs near the anus. Other choices are incorrect because pinworms do not reside in the duodenum (A), ileum (B), or transverse colon (C) as their primary location is in the lower gastrointestinal tract near the anus.