Viruses

1) What is a capsid?

A capsid is a protein shell that surrounds the genetic material.

2) How are the viruses that infect bacterial cells called?

Bacteriophages (Phages)

3) What does limited host range mean for viruses?

Viruses have a limited host range. This means they can infect only a very limited variety of hosts. Ex. human cold virus infects only cells of the upper respiratory tract.

Facts:

- Researchers discovered viruses in the late 1800s by studying a plant disease, tobacco mosaic disease.

- The genome of a virus can be single or double stranded DNA or RNA

- Phages can reproduce two alternative mechanisms: the lytic cycle and the lysogenic cycle.

- Viruses can reproduce only within cells

- Viroids are naked RNA molecules that infect plants and disrupt their growth.

Summary:

Viruses are particles of nucleic acids, proteins, and, in some cases, lipids. It is in common to all viruses that they enter living cells and, once inside, use the machinery of the infected cell to produce more viruses. Viruses are parasites, not considered to be living things because they are not made up of cells. Once the virus is inside a host cell, two different processes may occur and they are lytic infection and lysogenic infection.

There are viruses that cause diseases and they are called pathogens.

Extra:

HIV virus structure video