Nokea
The so-called “red tide†is generally caused by which of the following organisms?
- A. Lichens
- B. Bacteria
- C. Pfiesteria
- D. Dinoflagellates
Correct Answer: D
Rationale: The correct answer is D: Dinoflagellates. Red tides are caused by the rapid growth of certain species of dinoflagellates, which are single-celled algae. These algae produce toxins that can harm marine life and humans. Lichens (A) are not associated with red tides. While some bacteria (B) can contribute to harmful algal blooms, they are not the primary cause of red tides. Pfiesteria (C) is a type of harmful algal species, but it is not the main organism responsible for red tides. Therefore, the correct answer is dinoflagellates (D) due to their ability to cause red tides through toxin production.
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Which form of human plague is present with high fever and large lymphadenopathies (buboes). The case fatality in untreated cases may reach 60%.
- A. Bubonic plague
- B. Pneumonic plague
- C. Gastrointestinal plague
- D. Septicemic plague
Correct Answer: A
Rationale: The correct answer is A: Bubonic plague. Bubonic plague is characterized by high fever and large swollen lymph nodes (buboes). The case fatality rate in untreated cases can reach 60%. This form of plague is typically transmitted through the bite of an infected flea.
B: Pneumonic plague presents with respiratory symptoms and is transmitted through respiratory droplets.
C: Gastrointestinal plague is not a recognized form of plague.
D: Septicemic plague is a severe form of plague where the bacteria multiply in the bloodstream. It may not always present with buboes.
The typical site for replication of DNA viruses is:
- A. Nucleus
- B. Cytoplasm
- C. Endoplasmic Reticulum
- D. Golgi Apparatus
Correct Answer: A
Rationale: The correct answer is A: Nucleus. DNA viruses replicate in the host cell's nucleus because they require access to the host cell's DNA replication machinery. The nucleus contains the necessary enzymes and factors for DNA replication to occur accurately. The DNA viruses need to utilize these host cell components to replicate their own genetic material.
Summary of why other choices are incorrect:
B: Cytoplasm - Cytoplasm lacks the necessary enzymes and machinery for accurate DNA replication.
C: Endoplasmic Reticulum - ER is involved in protein synthesis and processing, not DNA replication.
D: Golgi Apparatus - Golgi apparatus is responsible for processing and packaging proteins, not DNA replication.
A child with diarrhea had stool microscopy revealing cysts with four nuclei. What is the most likely causative agent?
- A. Entamoeba histolytica
- B. Giardia lamblia
- C. Balantidium coli
- D. Trichomonas hominis
Correct Answer: A
Rationale: The correct answer is A: Entamoeba histolytica. This pathogen is known to cause amoebic dysentery, characterized by diarrhea with bloody or mucoid stools. The presence of cysts with four nuclei in the stool microscopy is a characteristic feature of Entamoeba histolytica. Other choices are incorrect because Giardia lamblia typically presents with binucleate cysts, Balantidium coli is a ciliated protozoan, and Trichomonas hominis is a non-pathogenic parasite found in the human intestine.
The movement of molecules through a membrane from an area of high hydrostatic pressure to an area of lower hydrostatic pressure is:
- A. filtration
- B. exocytosis
- C. simple diffusion
- D. simple diffusion
Correct Answer: D
Rationale: The correct answer is D: simple diffusion. In simple diffusion, molecules move from an area of high concentration to low concentration without the need for energy input. Hydrostatic pressure is a form of passive transport that drives molecules to equalize concentration. Filtration (A) involves the movement of solutes through a membrane under pressure. Exocytosis (B) is the process by which cells release substances outside the cell using energy. Osmosis (C) is the movement of water molecules across a selectively permeable membrane. Therefore, simple diffusion is the most appropriate choice in this scenario.
Acne is caused by:
- A. Staphylococcus aureus
- B. Staphylococcus epidermidis
- C. Streptococcus pyogenes
- D. Propionibacterium acnes
Correct Answer: D
Rationale: The correct answer is D: Propionibacterium acnes. This bacterium plays a key role in acne formation by colonizing hair follicles, leading to inflammation and acne lesions. It produces fatty acids that contribute to the development of acne. Staphylococcus aureus (A) and Staphylococcus epidermidis (B) are not directly linked to acne. Streptococcus pyogenes (C) is associated with skin infections but not acne. In summary, Propionibacterium acnes is the primary bacterium responsible for acne due to its ability to induce inflammation and follicular blockages.