Nokea
Which of the following transport mechanisms transports water across the plasma membrane?
- A. osmosis
- B. facilitated diffusion
- C. phagocytosis
- D. exocytosis
Correct Answer: A
Rationale: Osmosis is the correct answer because it is the process by which water molecules move across a semi-permeable membrane from an area of low solute concentration to an area of high solute concentration. This movement occurs passively, driven by the concentration gradient. Facilitated diffusion (B) involves the transport of specific molecules with the help of carrier proteins, not water. Phagocytosis (C) is a process where cells engulf solid particles, not water molecules. Exocytosis (D) is the process of releasing substances from a cell by fusion of vesicles with the cell membrane, not the transport of water across the membrane.
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It is planned to use the territory of an old cattle burial ground (which is not used for more than 50 years) for building houses. But ground analysis revealed presence of the pathogen of the very dangerous illness. Which of the indicated microorgonisms is likely to remain in the ground for such a long time?
- A. Mycobacterium bovis
- B. Brucella abortus
- C. Bacillus anthracis
- D. Francisella tularensis
Correct Answer: C
Rationale: Rationale:
1. Bacillus anthracis is a spore-forming bacterium that can survive for decades in the soil.
2. The spores are resistant to harsh conditions and can remain dormant for long periods.
3. This resilience allows Bacillus anthracis to persist in the old cattle burial ground for over 50 years.
4. Mycobacterium bovis, Brucella abortus, and Francisella tularensis are not known for long-term survival in soil.
Summary:
- Mycobacterium bovis, Brucella abortus, and Francisella tularensis do not have the spore-forming ability.
- Mycobacterium bovis causes tuberculosis in cattle.
- Brucella abortus causes brucellosis in cattle.
- Francisella tularensis causes tularemia in animals and humans.
Patients with similar complaints applied to the doctor: weakness, pain in the intestines, disorder of GIT. Examination of the feces revealed that one patient with four nucleus cysts should be hospitalized immediately. For what protozoa are such cysts typical?
- A. Lamblia
- B. Dysenteric amoeba
- C. Balantidium
- D. Trichomonas
Correct Answer: B
Rationale: The correct answer is B: Dysenteric amoeba.
1. Dysenteric amoeba causes amoebiasis, which presents with symptoms like weakness, intestinal pain, and gastrointestinal disorders.
2. The presence of four-nucleus cysts in the feces indicates an infection with Entamoeba histolytica, the causative agent of amoebiasis.
3. Multiple-nucleus cysts are characteristic of Entamoeba histolytica, distinguishing it from other protozoa.
4. Lamblia (choice A), Balantidium (choice C), and Trichomonas (choice D) are not associated with four-nucleus cysts or the mentioned symptoms, making them incorrect choices.
Which one is not true for the adaptive immunity:
- A. Is mainly observed in the skin and mucous membranes
- B. Develops immune memory
- C. Has a specificity
- D. Evolutionary newer in comparison to the innate immunity
Correct Answer: A
Rationale: The correct answer is A because adaptive immunity is not mainly observed in the skin and mucous membranes. Adaptive immunity is a systemic response that involves specific immune cells and antibodies targeting specific pathogens. It develops immune memory (B), meaning it can recognize and respond faster upon re-exposure to the same pathogen. Adaptive immunity also has specificity (C), as it can target specific antigens. Lastly, adaptive immunity is not evolutionarily newer in comparison to innate immunity (D), as both systems have co-evolved to provide comprehensive protection against pathogens.
The organism often called “flesh-eating bacteria†is:
- A. Staphylococcus aureus
- B. Staphylococcus epidermidis
- C. Streptococcus pyogenes
- D. Propionibacterium acnes
Correct Answer: C
Rationale: The correct answer is C: Streptococcus pyogenes. This bacterium is commonly known as "flesh-eating bacteria" due to its ability to cause severe tissue destruction and necrotizing fasciitis. Streptococcus pyogenes produces toxins that break down skin and muscle tissues. Staphylococcus aureus (A) can cause skin infections but is not typically associated with necrotizing fasciitis. Staphylococcus epidermidis (B) is a normal skin flora and rarely causes infections. Propionibacterium acnes (D) is associated with acne and not known for causing tissue destruction. Therefore, the correct choice is Streptococcus pyogenes due to its unique ability to cause severe tissue damage and necrotizing fasciitis.
Microscopic examination of a smear from a chancre revealed spiral microorganisms. The bacteria were thin and mobile with 8-12 regular coils. What is the likely diagnosis?
- A. Syphilis
- B. Leptospirosis
- C. Lyme disease
- D. Relapsing fever
Correct Answer: A
Rationale: The correct diagnosis is A: Syphilis. The spiral microorganisms described are characteristic of Treponema pallidum, the causative agent of syphilis. The thin and mobile bacteria with 8-12 regular coils match the morphology of Treponema pallidum. Leptospirosis is caused by Leptospira interrogans, which are thicker and have hook-like ends, different from the described bacteria. Lyme disease is caused by Borrelia burgdorferi, which has a different appearance than the thin, coiled bacteria in the smear. Relapsing fever is caused by Borrelia recurrentis, which typically have irregular coils, unlike the regular coils seen in the smear.