Final answer:
Viruses infect host cells and use the host's machinery and metabolism to produce new viral particles. They cannot generate their own ATP or carry out metabolic processes independently and require the host cell's ribosomes, ATP, and enzymes for replication.
Step-by-step explanation:
Viruses replicate by infecting a host cell and using the cell's machinery and metabolism to produce new copies of themselves. They lack the ability to generate their own ATP or to carry out metabolic processes independently. Instead, they rely on the host cell's ribosomes, ATP, enzymes, and other components to make viral proteins and replicate their nucleic acid. Therefore, the correct answer to the question is: Viruses use the host cell to copy themselves and make viral proteins.
Viruses have a basic structure, which includes a DNA or RNA core and an outer capsid made of proteins. Some have an additional phospholipid envelope. Once inside the host cell, a virus can commandeer cellular machinery to produce more viral particles. For example, DNA viruses use the host cell's machinery to synthesize additional DNA and mRNA for protein synthesis, while RNA viruses directly use their RNA as a template.
It is clear that viruses are different from living organisms in that they do not possess ribosomes or their own metabolic processes, and hence they cannot synthesize their own ATP or proteins without a host. This distinct mechanism is what characterizes viral replication.