Virus
What Is a Virus?
A virus is an extremely tiny infectious agent that is only able to live inside a *cell.
Viruses can be rod-shaped, sphere-shaped, or multisided. Some viruses look like tadpoles.
Basically, viruses are composed of just two parts. The outer part is a protective shell made of *protein. This shell is often surrounded by another protective layer or envelope, made of protein or lipids (fats). The inner part is made of genetic material, either *RNA or *DNA.
A virus does not have any other structures (called organelles) that living cells have, like a nucleus or mitochondria. These organelles are the tiny organs that maintain a cell's metabolism (life processes). A virus has no metabolism at all.
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