Nokea
A defined microorganism can be isolated in pure culture:
- A. From liquid and solid media
- B. From liquid nutrient media
- C. Only from single colonies on solid media
- D. None of the above
Correct Answer: C
Rationale: The correct answer is C because isolating a defined microorganism in pure culture involves obtaining a single, distinct colony on solid media. This ensures that only one type of microorganism is present in the culture, preventing contamination. Liquid media can harbor multiple organisms, making it challenging to isolate a specific microorganism. Therefore, choice A is incorrect. Choice B is also incorrect as liquid nutrient media does not provide the necessary isolation required for pure culture. Choice D is incorrect because isolating from single colonies on solid media allows for the pure culture of the defined microorganism.
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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.
The organisms to be identified have a nucleus surrounded by a nuclear membrane. Genetic material is concentrated predominantly in the chromosomes which consist of DNA strands and protein molecules. These cells divide mitotically. Identify these organisms:
- A. Eukaryotes
- B. Bacteriophages
- C. Prokaryotes
- D. Viruses
Correct Answer: A
Rationale: Step-by-step rationale:
1. The presence of a nucleus with a nuclear membrane indicates eukaryotic cells.
2. Eukaryotes have genetic material in chromosomes made of DNA and proteins.
3. Mitotic division is characteristic of eukaryotic cells.
4. Therefore, the organisms described are eukaryotes.
Summary:
- Bacteriophages (B) are viruses that infect bacteria.
- Prokaryotes (C) lack a nucleus and their genetic material is not organized into chromosomes.
- Viruses (D) are not considered living organisms and do not have a nucleus or chromosomes.
A blood culture from a patient with sepsis revealed Gram-positive cocci in pairs. The bacteria were catalase-negative and alpha-hemolytic. What is the most likely causative agent?
- A. Streptococcus pneumoniae
- B. Staphylococcus aureus
- C. Enterococcus faecalis
- D. Neisseria gonorrhoeae
Correct Answer: A
Rationale: The correct answer is A: Streptococcus pneumoniae. This is because the bacterium is Gram-positive cocci in pairs, catalase-negative, and alpha-hemolytic, which are characteristic features of S. pneumoniae. The other choices can be ruled out based on specific characteristics: B) Staphylococcus aureus is catalase-positive, C) Enterococcus faecalis is gamma-hemolytic, and D) Neisseria gonorrhoeae is a Gram-negative diplococcus. Therefore, based on the given information, S. pneumoniae is the most likely causative agent of the sepsis.
Erysipelas is a bacterial infection characterised by well-defined areas of bright-red, inflamed and rough or leathery skin. Which one is the causative agent:
- A. Pseudomonas aeruginosa
- B. Staphylococcus aureus
- C. Streptococcus pyogenes
- D. Candida albicans
Correct Answer: C
Rationale: Step-by-step rationale for Choice C (Streptococcus pyogenes) being the correct answer:
1. Erysipelas is a skin infection characterized by well-defined red, inflamed skin areas.
2. Streptococcus pyogenes is a common causative agent of erysipelas.
3. This bacterium produces enzymes that break down skin proteins, leading to the characteristic symptoms of erysipelas.
4. Streptococcus pyogenes is known for causing skin infections, including erysipelas.
Summary of why the other choices are incorrect:
A. Pseudomonas aeruginosa: Typically causes opportunistic infections, but not commonly associated with erysipelas.
B. Staphylococcus aureus: Can cause skin infections, but not typically associated with erysipelas.
D. Candida albicans: Fungal infection, not a bacterium, and not known to cause erysipelas.
A patient consulted a doctor about bowels disfunction. The doctor established symptoms of duodenitis and enteritis. Laboratory examination helped to make the following diagnosis: lambliosis. What medication should be administered?
- A. Metronidazole
- B. Erythromycin
- C. Monomycin
- D. Chingamin
Correct Answer: A
Rationale: Rationale: Metronidazole is the drug of choice for treating lambliosis due to its effectiveness against Giardia lamblia, the parasite causing the infection. Metronidazole works by disrupting the DNA structure of the parasite, leading to its death. Erythromycin (choice B) is not effective against Giardia lamblia. Monomycin (choice C) and Chingamin (choice D) are not commonly used for treating lambliosis. Therefore, choice A, Metronidazole, is the correct medication for this patient.