Nokea
Diatoms, major components of marine phytoplankton, belong to:
- A. Chrysophyta
- B. Rhodophyta
- C. Chlorophyta
- D. Phaeophyta
Correct Answer: A
Rationale: The correct answer is A: Chrysophyta. Diatoms are classified under the division Chrysophyta due to their unique characteristics, such as possessing a cell wall made of silica (siliceous frustule) and containing chlorophyll a and c for photosynthesis. Chrysophyta includes golden-brown algae, which diatoms are a part of. Rhodophyta (B) includes red algae, Chlorophyta (C) includes green algae, and Phaeophyta (D) includes brown algae. These choices are incorrect as they do not align with the specific characteristics and classification of diatoms within the kingdom Protista.
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Giardiasis is a waterborne gastrointestinal disease caused by Giardia intestinalis, which is a:
- A. protozoan
- B. bacterium
- C. fungus
- D. virus
Correct Answer: A
Rationale: Step 1: Giardiasis is caused by Giardia intestinalis, which is a well-known protozoan parasite.
Step 2: Protozoans are single-celled eukaryotic organisms commonly found in water sources.
Step 3: Giardia intestinalis infects the intestine, causing symptoms like diarrhea and abdominal cramps.
Step 4: Bacteria (Choice B) are prokaryotic organisms, different from protozoans.
Step 5: Fungi (Choice C) are also eukaryotic but are not responsible for causing Giardiasis.
Step 6: Viruses (Choice D) are not cellular and cannot independently cause Giardiasis.
In summary, the correct answer is A (protozoan) because Giardia intestinalis is a protozoan parasite specifically known to cause Giardiasis, while the other choices (Bacterium, Fungus, Virus) do not match the characteristics of the
Which statement is correct? Yersinia pestis is the causative agent of:
- A. Cholera
- B. AIDS
- C. Plague
- D. None of the above
Correct Answer: C
Rationale: The correct answer is C: Plague. Yersinia pestis is a bacterium that causes plague, a serious infectious disease transmitted through infected fleas or direct contact with infected animals. Yersinia pestis does not cause Cholera (choice A) or AIDS (choice B). Choice D, None of the above, is incorrect as Yersinia pestis is indeed the causative agent of plague.
A fetus infected with rubella virus produces which of the following antibodies that can then be detected in the umbilical cord?
- A. IgA
- B. IgM
- C. IgG
- D. IgD
Correct Answer: B
Rationale: The correct answer is B: IgM. IgM antibodies are the first type of antibodies produced in response to an infection, indicating an active or recent infection. In the case of a rubella virus infection in a fetus, IgM antibodies can be detected in the umbilical cord blood, confirming the presence of the virus. IgA antibodies are mainly found in mucosal areas, IgG antibodies indicate past infection or immunity, and IgD antibodies play a role in B cell activation but are not typically detected in this context.
Which of the following bacteria produce endotoxins?
- A. Streptococcus pneumoniae
- B. Clostridium tetani
- C. Escherichia coli
- D. Staphylococcus aureus
Correct Answer: C
Rationale: The correct answer is C: Escherichia coli. E. coli is a gram-negative bacterium, which means it has an outer membrane containing lipopolysaccharides (LPS), also known as endotoxins. Endotoxins are released when the bacterium is destroyed, causing an inflammatory response.
Streptococcus pneumoniae (choice A) is a gram-positive bacterium and does not produce endotoxins. Clostridium tetani (choice B) produces exotoxins, not endotoxins. Staphylococcus aureus (choice D) is also a gram-positive bacterium and does not produce endotoxins.
In summary, E. coli is the correct answer because it is a gram-negative bacterium that produces endotoxins, while the other choices are gram-positive bacteria that do not produce endotoxins.
A patient with pneumonia had sputum cultured, revealing Gram-negative diplococci. The bacteria were oxidase-positive and fermentative. What is the most likely causative agent?
- A. Neisseria meningitidis
- B. Neisseria gonorrhoeae
- C. Moraxella catarrhalis
- D. Haemophilus influenzae
Correct Answer: A
Rationale: The correct answer is A: Neisseria meningitidis. This is because Neisseria meningitidis is a Gram-negative diplococcus that is oxidase-positive and fermentative. Neisseria gonorrhoeae is also a Gram-negative diplococcus, but it is not fermentative. Moraxella catarrhalis is oxidase-positive but not fermentative. Haemophilus influenzae is Gram-negative but is not a diplococcus, and it is not fermentative. Therefore, based on the characteristics provided in the question, Neisseria meningitidis is the most likely causative agent.