Nokea
Microscopy of a smear obtained from a patient with acute purulent periostitis revealed gram-positive bacteria arranged in clusters resembling bunch of grapes. What microorganisms is this morphology typical for?
- A. Staphylococci
- B. Sarcina
- C. Tetracocci
- D. Candida fungi
Correct Answer: A
Rationale: Rationale:
Staphylococci are gram-positive bacteria that typically arrange in clusters resembling a bunch of grapes. This characteristic morphology is specific to staphylococci due to their division pattern. Sarcina, Tetracocci, and Candida fungi do not exhibit this clustering pattern. Staphylococci are commonly associated with purulent infections, making them the most likely microorganisms in this scenario.
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After a prolonged isoniazid treatment, the patient developed polyneuritis, paresthesia, memory disorders, and convulsions. What is the most likely mechanism of the described isoniazid side-effects?
- A. Disruption of cell membrane synthesis
- B. Inhibition of protein synthesis
- C. Inhibition of RNA-synthesis
- D. Inhibition of pyridoxal phosphate synthesis
Correct Answer: D
Rationale: The correct answer is D. Isoniazid inhibits pyridoxal phosphate synthesis, which is the active form of vitamin B6. Pyridoxal phosphate is essential for various enzymatic reactions, including neurotransmitter synthesis and myelin formation. Therefore, isoniazid-induced pyridoxal phosphate deficiency can lead to neurological symptoms like polyneuritis, paresthesia, memory disorders, and convulsions.
A: Disruption of cell membrane synthesis - This is not the mechanism of isoniazid side-effects.
B: Inhibition of protein synthesis - Isoniazid does not directly inhibit protein synthesis.
C: Inhibition of RNA-synthesis - Isoniazid does not inhibit RNA synthesis; it affects vitamin B6 metabolism.
Streptococci are:
- A. Gram-positive, short rod shaped bacteria and size 4-6 µm
- B. Gram-negative, rounded or lanceolate shape and size 0,5-1 µm
- C. Gram-negative, short rod shaped bacteria and size 4-6 µm
- D. Gram-positive, spherical or lanceolate shape and size 0,5-1 µm
Correct Answer: D
Rationale: The correct answer is D because Streptococci are Gram-positive bacteria, typically spherical in shape, and range from 0.5-1 µm in size.
A is incorrect as streptococci are not rod-shaped and are usually smaller in size. B is incorrect as they are not Gram-negative and are not typically of such small size.
C is incorrect as streptococci are not Gram-negative and are not usually rod-shaped. Thus, based on their characteristics, the correct answer is D.
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.
The prokaryotic cell does not possess:
- A. Ribosomes
- B. Endoplasmic reticulum
- C. Chromosome
- D. Peptidoglycan
Correct Answer: B
Rationale: The correct answer is B: Endoplasmic reticulum. Prokaryotic cells lack membrane-bound organelles like the endoplasmic reticulum, which is present in eukaryotic cells. Prokaryotes do possess ribosomes for protein synthesis (A), a chromosome (C) for genetic material, and peptidoglycan (D) in their cell walls. The absence of endoplasmic reticulum is a key characteristic that distinguishes prokaryotic cells from eukaryotic cells.
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.