BOTANY

Detailed explanation-1: -A virus is a tiny, infectious particle that can reproduce only by infecting a host cell. Viruses “commandeer” the host cell and use its resources to make more viruses, basically reprogramming it to become a virus factory. Because they can’t reproduce by themselves (without a host), viruses are not considered living.

Detailed explanation-2: -They do not possess ribosomes and cannot independently form proteins from molecules of messenger RNA. Because of these limitations, viruses can replicate only within a living host cell.

Detailed explanation-3: -Viruses are not able to replicate without the metabolic machinery of the cell.

Detailed explanation-4: -All viruses are obligate parasites; that is, they lack metabolic machinery of their own to generate energy or to synthesize proteins, so they depend on host cells to carry out these vital functions.

Detailed explanation-5: -Viruses cannot reproduce outside a living cell because they lack the cellular organisation and independent machinery which is required for the reproduction and other metabolic activities. They can only multiply inside the living cell of host by using host’s cellular machinery.