What is a virus? Tiny organisms that may lead to mild to severe illnesses in humans, animals, and plants

How big are viruses? 100 times smaller than a single bacteria cell bacteria cell is 10 times smaller than a human cell human cell 10 times smaller that the diameter of a single human hair

Are viruses alive? Viruses by themselves are not alive. They cannot grow or multiply on their own and need to enter a human or animal cell and take over the cell to help them multiply. May also infect bacterial cells

The virus particle or the virions attack the cell and take over its machinery to carry out their own life processes of multiplication and growth. An infected cell will produce viral particles instead of its usual products.

Structure of a virus A virion (virus particle) has three main parts: Nucleic acid – this is the core of the virus with the DNA or RNA. The DNA or RNA holds all of the information for the virus and that makes it unique and helps it multiply. Protein Coat (capsid) – This is covering over the nucleic acid that protects it. Lipid membrane (envelope) – this covers the capsid. Many viruses do not have this envelope and are called naked viruses.

How do viruses infect? Viruses do not have the chemical machinery needed to survive on their own. They, thus seek out host cells in which they can multiply. These viruses enter the body from the environment or other individuals from soil to water to air via nose, mouth, or any breaks in the skin and seek a cell to infect.

Life cycle of a basic virus There are a few basic steps that all infecting viruses follow and these are called the lytic cycle. These include: A virus particle attaches to a host cell (process of adsorption) The particle injects its DNA or RNA into the host cell (entry) The invading DNA or RNA takes over the cell and recruits the host’s enzymes The cellular enzymes start making new virus particles (replication) The particles of the virus created by the cell come together to form new viruses (assembly) The newly formed viruses kill the cell so that they may break free and search for a new host cell (release)

How a virus enters your body http://www.youtube.com/watch?feature=player_embedded&v=Rpj0emEGShQ