An agricultural researcher isolates an ultra-microscopic infectious agent from cassava leaves displaying mosaic symptoms. Biochemical assays indicate that the agent consists solely of a single-stranded RNA core surrounded by a protein coat (capsid). The agent fails to reproduce in a sterile cell-free nutrient broth containing free amino acids, nucleotides, and ATP, but replicates rapidly upon inoculation into living host tissue. Which characteristic of the pathogen explains its inability to multiply in the cell-free medium?
- It lacks autonomous metabolic machinery and protein-synthesizing organelles, functioning strictly as an obligate intracellular parasite.Cevap
- BIts rigid peptidoglycan envelope requires active transport proteins to absorb dissolved nutrients from host cell walls.
- CIt requires its own cytoplasm-bound mitochondria to generate metabolic energy for extracellular division.
- DIt carries out saprophytic extracellular digestion of nutrient broth before undergoing binary fission.
Cevap
It lacks autonomous metabolic machinery and protein-synthesizing organelles, functioning strictly as an obligate intracellular parasite.
The correct option correctly identifies that viruses are acellular entities lacking ribosomes, organelles, and metabolic machinery. Because they cannot synthesize their own capsid proteins or copy their nucleic acids independently, they require living host cells to hijack host ribosomal and enzymatic systems.
Adım Adım Çözüm
Anahtar Kavram
Viruses are acellular obligate intracellular parasites that depend entirely on the host cell metabolic and organelle systems for replication.
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