1. Viruses

2. Is a Virus Alive? Lets first look at organisms we know are alive?
What can you tell by comparing the virus to the cells we have learned about?

3. What is a Virus?
Viruses- segments of nucleic acids contained in a protein coat.
Viruses are not cells and not alive.
Smaller than prokaryotic cells.
Replicate by infecting host cells and using the host DNA to make more viruses.
Viruses do not grow, do not have homeostasis, and do not metabolize.

4. Why are viruses important?
Pathogens- agents that cause disease.
Viruses are often restricted to certain kinds of cells.
Ex. HIV infects immune cells of animals.
Ex. Bacteriophages- viruses that infect bacteria.

5. Discovery Late 1800’s in tobacco plant and identified in 1935
TMV (tobacco mosaic virus)- stunts the growth of tobacco plant.

6. Structure Capsid- virus protein coat.
contain either RNA or DNA, but not both.
Envelope- membrane surrounding capsid.
Helps virus enter cell.
Glycoproteins- projections on envelope made of proteins & carbohydrate molecule, derived from host cell. Helps virus attach to host.
Glycoproteins

7. Bacteriophage Structure

8. Viral Shapes
Spherical
Helical
Rod Shaped
Polyhedral

9. Viral Categories
Viruses divided into 2 categories based on whether they contain RNA or DNA.
RNA
DNA
HIV – Human Immunodeficiency Virus
Warts – Human papillomavirus
FLU – Influenza Virus
Chicken Pox – Varicella Zoster Virus
Rabies – Rabies Virus
Mononucleosis – Epstein-Barr Virus
Hepatitis C – Hepatitis
Genital Herpes - Herpes simplex 2, can be 1
Rabies
Flu
Herpes Virus
Mononucleiosis

10. Replication – 2 Types
Lytic cycle- viral infection, then replication, and then cell destruction.
Once cell is destroyed, the viruses are then released.
Lysogenic cycle- virus stays inside cell but do not make new viruses.
Viral gene is inserted into the host chromosome which is called a provirus. When the cell divides the provirus divides.
Virus replicated without destroying cell.
example: Herpes virus

13. Assignment Draw a diagram of a Bacteriaphage and an spherical Virus.
Label, color, and give some examples of each.
Pg. 437 and pg. 192