Nokea
Microscopic examination of a patient's duodenal contents revealed protozoa with two nuclei, four flagella, and a ventral adhesive disc. What is the likely causative agent?
- A. Giardia lamblia
- B. Leishmania donovani
- C. Entamoeba coli
- D. Trypanosoma gambiense
Correct Answer: A
Rationale: The correct answer is A: Giardia lamblia. This protozoan matches the description of the causative agent because it has two nuclei, four flagella, and a ventral adhesive disc. Giardia lamblia is commonly found in the duodenum and causes giardiasis. The other choices can be eliminated because Leishmania donovani causes visceral leishmaniasis, not the described symptoms. Entamoeba coli is a non-pathogenic amoeba found in the large intestine. Trypanosoma gambiense causes African trypanosomiasis and is transmitted by the tsetse fly, not matching the described characteristics.
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Viral capsomeres are composed of subunits called
- A. envelopes.
- B. protomeres.
- C. capsids.
- D. nucleoids.
Correct Answer: B
Rationale: The correct answer is B: protomeres. Viral capsomeres are the building blocks of viral capsids, which are protein coats that enclose and protect the viral genetic material. These capsomeres are made up of smaller subunits called protomeres. Envelopes (A) refer to a lipid membrane surrounding some viruses, not the subunits of capsomeres. Capsids (C) are the protein coats that capsomeres make up, not the subunits themselves. Nucleoids (D) are found in bacterial cells and refer to the region where the genetic material is located, not the subunits of viral capsomeres.
The following viruses are referred to the Filoviridae family:
- A. Lassa virus and lymphocytic choriomeningitis viruses
- B. Chikungunya virus and Sindbis virus
- C. Marburg virus and Ebola virus
- D. Crimean-Congo virus and Hantaan virus
Correct Answer: C
Rationale: Step-by-step rationale:
1. The Filoviridae family includes Marburg virus and Ebola virus.
2. Both viruses are characterized by filamentous, enveloped structure.
3. They cause severe hemorrhagic fever in humans.
4. Lassa virus and lymphocytic choriomeningitis viruses belong to Arenaviridae.
5. Chikungunya virus and Sindbis virus are alphaviruses.
6. Crimean-Congo virus and Hantaan virus are bunyaviruses.
7. Therefore, the correct answer is C.
Bacteria that grow in the absence of oxygen are called:
- A. Obligate aerobes
- B. Facultative anaerobes
- C. Obligate anaerobes
- D. Aerotolerant anaerobes
Correct Answer: C
Rationale: The correct answer is C: Obligate anaerobes. These bacteria cannot survive in the presence of oxygen as they lack the necessary enzymes to detoxify reactive oxygen species. Obligate aerobes (A) require oxygen, facultative anaerobes (B) can grow with or without oxygen, and aerotolerant anaerobes (D) can survive in the presence of oxygen but do not utilize it for growth.
The enzyme that breaks down the peptidoglycan in bacterial cell walls is:
- A. Lysozyme
- B. Amylase
- C. Protease
- D. Lipase
Correct Answer: A
Rationale: The correct answer is A: Lysozyme. Lysozyme is an enzyme that targets and breaks down the peptidoglycan in bacterial cell walls by cleaving the glycosidic bonds between the sugar components. This action weakens the cell wall, leading to bacterial cell lysis. Amylase (B) breaks down starch, not peptidoglycan. Protease (C) breaks down proteins, not peptidoglycan. Lipase (D) breaks down lipids, not peptidoglycan. Therefore, Lysozyme is the correct enzyme for breaking down peptidoglycan in bacterial cell walls.
Which of the following bacteria is responsible for causing the plague?
- A. Yersinia pestis
- B. Clostridium difficile
- C. Neisseria gonorrhoeae
- D. Pseudomonas aeruginosa
Correct Answer: A
Rationale: The correct answer is A: Yersinia pestis. Y. pestis is responsible for causing the plague, a severe infectious disease. This bacterium is transmitted via fleas from rodents to humans. It causes bubonic, septicemic, and pneumonic plague. Clostridium difficile causes gastrointestinal infections, Neisseria gonorrhoeae causes gonorrhea, and Pseudomonas aeruginosa can cause various infections but not the plague.