1. Virus Notes TEK 4C

2. Section 18.1 Summary – pages 475-483 Viruses are composed of nucleic acids enclosed in a protein coat and are smaller than the smallest bacterium. What is a Virus?

3. Section 18.1 Summary – pages 475-483 Viruses are considered nonliving because: They are NOT cells. They don’t carry out respiration, grow, or develop. They do not reproduce like living cells. What is a Virus?

4. Viruses cannot reproduce without the help of a living cell. Viruses infect a host cell and inject their DNA/RNA.

5. A cell in which a virus replicates inside of is called the host cell. What is a Host Cell?

6. Section 18.1 Summary – pages 475-483 Before a virus can replicate, it must enter a host cell. A virus recognizes and attaches to a host cell when one of its proteins attaches with a molecular shape that is the receptor site on the host cell’s plasma membrane. Virus

7. Section 18.1 Summary – pages 475-483 Each virus has a specifically shaped attachment protein. Therefore, each virus can usually attach to only a few kinds of cells. In general, viruses are species specific, and some also are cell-type specific. For example, polio viruses normally infect only intestinal and nerve cells. Viral Attachment to Host

8. Section 18.1 Summary – pages 475-483 A virus has an inner core of nucleic acid, either RNA or DNA and an outer protein coat called a capsid. Capsid Nucleic acid Viral Structure

9. Section 18.1 Summary – pages 475-483 Some larger viruses, such as human flu viruses, may have an additional layer, called an envelope, surrounding their capsids. Capsid Nucleic acid Envelope Viral Structure Envelopes are composed primarily of the same materials found in the plasma membranes of all cells.

10. Polyhedral virus shape Human Papilloma Virus Envelope studded with projections (flu and AIDS) VIRUS SHAPES

11. Long narrow helical shape (Tobacco Mosaic Virus) Polyhedral-shaped head attached to a cylindrical tail with leg-like fibers VIRUS SHAPES

12. Viruses and Disease

13. A vaccine is an injection of particles of viruses or bacteria that provide the human body with a defense against disease.

14. Antibiotics are ineffective against viral infections. For bacterial infections, antibiotics are a good option.

15. Common Viral Diseases Influenza Common Cold Chicken Pox

16. Common Viral Diseases Small Pox HIV / AIDS HIV attacking T-Cell West Nile Virus Transmitted by mosquito