Which of the following are typical components of a virus?

• A. Nucleic acid, capsid, envelope
• B. Ribosomes and mitochondria
• C. Cell wall and plasma membrane
• D. Chloroplasts and vacuoles

Answer: (A)

Viruses are acellular particles that carry genetic material inside a protective protein shell, and many also have a lipid envelope surrounding that shell. This combination—nucleic acid plus a capsid, with an envelope in many viruses—defines a typical virion. Ribosomes and mitochondria are cellular components found inside host cells, not viruses. Viruses don’t have their own cell wall or plasma membrane; when an envelope is present, it’s a membrane borrowed from the host, not a separate viral membrane. Chloroplasts and vacuoles are plant cell organelles and are not part of viruses. So the classic make-up of a virus is nucleic acid, a capsid, and an envelope in those that have one.