MDCAT Biology · Biology · Acellular life. The idea in plain words, the rules to remember, the mistake to avoid and a worked example, written and checked by Mega Lecture.
A virus is not a cell. It has no cytoplasm, no ribosomes and no metabolism of its own, so it is called acellular. It can multiply only inside a living host cell, which makes it an obligate intracellular parasite.
Every virus has a core of nucleic acid, either DNA or RNA but never both, inside a protein coat called the capsid. The capsid is built from protein subunits called capsomeres. Some viruses also have an outer envelope, taken from the host cell membrane and carrying viral glycoproteins.
Viruses are classified by their nucleic acid, the symmetry of the capsid, the host they infect and the disease they cause.
Saying that a virus contains both DNA and RNA, or mixing up capsid and capsomere. One virus has one kind of nucleic acid only, and many capsomeres make one capsid.
Answer: It is not a virus. It must be a very small cell, such as a tiny bacterium.
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