Q.Describe the chemical structure of viruses.

[!TLDR]

The question asks for a description of the chemical structure common to viruses.

[!ANSWER]

A virus is chemically built from a nucleic acid core (either DNA or RNA, never both) enclosed by a protein coat called the capsid, made of repeating subunits called capsomeres, with some viruses additionally having an outer lipid envelope.

Chemically, every virus particle (or virion) is constructed from the same two essential components. At its core is a nucleic acid, which carries the virus's genetic information; unlike a cell, a single virus contains only one type of nucleic acid, either DNA or RNA, never both together, and this nucleic acid may be single-stranded or double-stranded. Surrounding the nucleic acid is a protective protein coat called the capsid, built up from many repeating protein subunits known as capsomeres, which protects the genetic material and plays a role in attaching the virus to a host cell. Some viruses additionally carry an outer envelope, a further layer containing lipid, derived from the membrane of a host cell the virus previously infected, wrapped around the capsid - though many viruses, including TMV and the T-even bacteriophages, lack such an envelope altogether.

[!ANSWER]

The chemical structure of a virus is, at minimum, a nucleic acid core (DNA or RNA) enclosed by a capsomere-built protein capsid, with an optional outer lipid envelope in some viruses.

• Stating that a virus contains both DNA and RNA, when in fact a single virus particle carries only one type of nucleic acid.
• Omitting the capsomeres as the repeating protein subunits that build up the capsid.