Viruses

Viruses are the smallest of all the microorganisms. They aren't cells, but are an arrangement of genetic material and protein that invade other living cells and take over their biochemistry to make other viruses. It is because if this that they are still classed a sliving organisms.

They are usually geometric shapes and have similar basic structures. However there is variation in the genetic material they carry, the structure of their protin coat and whether or not they have an evelope. The protein coat is made up of repeating protein units arranged in different ways. In some viruses this is covered by a lipid envelope, prooduced from the host cell. This makes it easier for the virus to pass from cell to cell. Viral genetic material can be DNA or RNA and the nucleic acid is sometimes double stranded, sometimes single. Viral DNA acts directly as a template for both new viral DNA and for mRNA needed to induce synthesis of viral proteins. Viral RNA directs the synthesis of an exzyme called reverse transcriptase that makes DNA molecules correpoding to the viral genome. This DNA is used as a template…