An ultra-filtrable infectious agent isolated from diseased plant tissue is subjected to quantitative biochemical analysis. Results confirm that the particle consists solely of single-stranded RNA enclosed within a capsid made of repeating capsomere proteins, completely lacking cytoplasm, ribosomes, and metabolic enzymes. When placed in a sterile, nutrient-rich synthetic growth medium containing glucose, amino acids, and essential salts, the agent exhibits zero metabolic activity and fails to replicate. Which of the following best accounts for the failure of this agent to multiply in the synthetic medium?
- It is an acellular obligate intracellular parasite that lacks independent metabolic machinery and relies entirely on host cell organelles for replication.Answer
- BIts rigid peptidoglycan cell wall prevents passive diffusion of glucose and amino acids required for binary fission outside a host.
- CIt is a primitive cellular organism whose plasma membrane and cytoplasm require host-derived regulatory hormones to activate cell division.
- DThe ambient temperature of the synthetic medium causes immediate thermal denaturation of its metabolic enzymes.
Answer
The pathogen fails to replicate in the synthetic medium because it is an acellular obligate intracellular parasite that lacks independent metabolic machinery and requires host cell organelles for replication.
The correct option accurately identifies viruses as acellular, obligate intracellular parasites. Because viral particles lack cellular components such as cytoplasm, ribosomes, and metabolic enzyme systems, they cannot synthesize proteins or generate energy independently. Consequently, they cannot multiply on cell-free synthetic nutrient media and require living host cells to replicate.
Step-by-Step Solution
Key Concept
Acellular Nature and Obligate Intracellular Parasitism of Viruses
Estimated Time:1m 15s