Nokea
The oldest fossils of prokaryotes go back __________ billion years.
- A. 4.0 to 5.0
- B. 3.5 to 4.0
- C. 2.5 to 3.0
- D. 2.2 to 2.7
Correct Answer: B
Rationale: The correct answer is B: 3.5 to 4.0 billion years. This range aligns with the oldest known fossils of prokaryotes found in ancient rocks. Fossils dating back to this time period provide evidence of early life forms on Earth. Choices A, C, and D are incorrect because they fall outside the established timeline based on scientific evidence and fossil records. A (4.0 to 5.0 billion years) is too early for the oldest prokaryote fossils, as it predates the formation of Earth's atmosphere suitable for life. C (2.5 to 3.0 billion years) and D (2.2 to 2.7 billion years) are too recent for the oldest prokaryote fossils, as life is believed to have originated much earlier.
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A 30-year-old patient complains about having abdominal pain and diarrhea for five days; body temperature rise up to 37, 5oC along with chills. The day before a patient had been in a forest and drunk from an open water reservoir. Laboratory analyses enabled to make the following diagnosis: amebic dysentery. What is the drug of choice for its treatment?
- A. Metronidazole
- B. Furazolidonum
- C. Levomycetin
- D. Phthalazol
Correct Answer: A
Rationale: The correct answer is A: Metronidazole.
Rationale:
1. Metronidazole is the drug of choice for amebic dysentery due to its effectiveness against the causative agent, Entamoeba histolytica.
2. Metronidazole has good tissue penetration and is able to reach the site of infection in the gut.
3. It is a bactericidal drug that acts by disrupting the DNA structure of the parasite.
4. Metronidazole is well-absorbed orally and has minimal side effects.
Summary of other choices:
B: Furazolidonum - Not the drug of choice for amebic dysentery. It is primarily used for treating bacterial diarrhea.
C: Levomycetin - Not effective against Entamoeba histolytica and not recommended for amebic dysentery.
D: Phthalazol - Not commonly used for amebic dysentery treatment. Metronidazole is preferred due
The infectious (non-sterile) immunity is:
- A. cross-reactivity of antibodies
- B. toxemia and formation of antitoxic antibodies
- C. persistence of infectious agent
- D. neutralization of infectious agent
Correct Answer: C
Rationale: The correct answer is C because infectious (non-sterile) immunity is achieved through the persistence of the infectious agent in the body, allowing the immune system to continuously recognize and combat the pathogen. This type of immunity provides long-lasting protection against future infections by the same agent.
Choice A (cross-reactivity of antibodies) is incorrect as it refers to the ability of antibodies to recognize similar antigens, not necessarily related to infectious immunity.
Choice B (toxemia and formation of antitoxic antibodies) is incorrect as it specifically relates to toxins produced by pathogens and the corresponding antibody response, not the persistence of the infectious agent itself.
Choice D (neutralization of infectious agent) is incorrect as it describes the process of antibodies binding to and inactivating pathogens, but it does not necessarily lead to long-term immunity through the persistence of the infectious agent.
The time response measures all of the following except:
- A. ED50
- B. Peak effect time
- C. Onset of response
- D. Threshold level
Correct Answer: A
Rationale: The correct answer is A: ED50. The time response does not measure the ED50 because ED50 refers to the effective dose needed to produce a response in 50% of the population, which is a dose-related concept, not a time-related one. Peak effect time, onset of response, and threshold level are all time-related measures in pharmacology. Peak effect time is the time taken to reach the maximum response, onset of response is the time taken for the response to start, and threshold level is the minimum dose or concentration required to produce a response. Therefore, A is the correct answer as it is the only choice that is not a time-related measure in this context.
Immunity after single vaccination against tetanus - application of tetanus toxoid is:
- A. intense and usually life long
- B. of limited duration, booster vaccinations are needed
- C. infectious (non-sterile)
- D. no correct answer
Correct Answer: B
Rationale: The correct answer is B. Immunity after a single tetanus vaccination is of limited duration, usually around 10 years. Booster vaccinations are needed to maintain protection due to waning immunity over time. Choice A is incorrect as immunity is not usually lifelong. Choice C is incorrect as tetanus toxoid is a sterile vaccine and does not cause infection. Choice D is also incorrect as there is a correct answer, which is B.
For infections caused by coronaviruses is NOT true that;
- A. Most commonly associated with URT infections
- B. May be asymptomatic
- C. SARS is an atypical pneumonia that can be complicated with acute respiratory failure and can cause death
- D. Reinfections cannot be observed
Correct Answer: D
Rationale: Step-by-step rationale for why answer choice D is correct:
1. Coronaviruses can cause reinfections due to potential waning immunity.
2. Studies have shown cases of reinfections with different strains or within a short period.
3. This contradicts the notion that reinfections cannot be observed.
Summary:
A: Incorrect because some coronaviruses can cause lower respiratory tract infections.
B: Incorrect as coronaviruses can exhibit varied symptomatology including asymptomatic cases.
C: Incorrect as some coronaviruses like SARS can lead to severe pneumonia and complications.