Viruses

1. Viruses

2. Virus • A non living particle composed of a nucleic acid and a protein coat • Causes many diseases • Can change how a cell functions • Study of viruses is called virology

3. Characteristics • One of the smallest biological particles capable of causing disease • Range from 20 nm to 25 nm • Nm (nanometers) • Uses the organelles and enzymes from the host cells • Not considered living organisms • No nucleus, cytoplasm, organelles,or cell membrane • Replicate only by infecting other cells

4. Structure • Protein coat called a capsid • May have DNA or RNA • Envelope – membrane made mostly of lipids taken from the host cell. It allows new viruses to infect host cells during the first stage of viral replication • Glycoprotein's – projections that contain sugar chains that viruses use to attach to host cells

5. Shape • Can be an Icosahedron – a geometric shape that has 20 triangular faces. • Helix – looks like a coiled spring

6. Virus Types • DNA virus – can directly produce RNA that makes more viral proteins or it may join with the host cell DNA to direct synthesis of new viruses. • RNA virus – Viral RNA is released into the host cells cytoplasm and uses the host cell ribosomes to produce new viral proteins • Retroviruses – a type of RNA virus that contains an enzyme called reverse transcriptase which it uses to make DNA

7. Bacteriophage infectionsLytic Infection • In a lytic infection, a virus enters a cell, makes copies of itself, and causes the cell to burst burst = lyse

8. Lysogenic Infection • In a lysogenic infection, a virus integrates its DNA into the DNA of the host cell, and the viral genetic information replicates along with the host cell’s DNA

9. Examples of Viruses HANTA VIRUS HIV VIRUS

10. Viroids • Smallest known particles able to replicate – consists of a short single strand of RNA and no capsid • Disrupts plant cell metabolism and can damage crops

11. Prions • Abnormal forms of proteins that clump together inside of a cell • This clumping activity eventually leads to the death of the cell

12. Prevention and Treatment • Antiviral Drugs – drugs that interfere with viral nucleic acid synthesis • Vaccines – A preparation of pathogens or other materials that stimulate the bodys immune system 2 types • Inactivated viruses – do not replicate in a host system • Attenuated viruses – viruses that have been genetically altered so that they are incapable of causing disease.