1. Viruses & Disease Chapter 19 Herpes virus

2. Virus- Latin for poison 1.A virus is a non-living particle made up of a.genetic material (DNA or RNA; NOT both) b.protein coat (capsid) 2. Can invade living cells. 3. Reproduce inside living cells. 4.Viruses ARE NOT CELLS! Slide # 2 Protein coat Nucleic acid Tail Tail Fibers A virus depends upon a living cell for its existence, harming that organism in the process. Parasites

3. Relative Sizes of Viruses Slide # 3

4. The Structure Of a Virus 1. Viruses are made of a core of DNA or RNA surrounded by a protein coat (capsid) 2. The Nucleic core is either made up of DNA or RNA but NOT both. Slide # 4 Bacteriophage: a virus that infects a bacterium.

5. TAKS Practice One characteristic shared by a virus and a living cell is that both — F store genetic information in nucleic acids G have a crystalline structure H gain energy directly from the sun J use glucose for respiration Correct answer: F Autotrophs / producers Cells do this Cells don’t have this Cells & viruses DO Slide # 5

6. E. coli Infected with a Bacteriophage What it looks like in real life. Bacteria are destroyed as viruses are released. E. coli Bacteriophage Slide # 6

7. How Viruses Infect a Host Cell A virus is specific in the type of cell it invades. Proteins on the virus capsid attach to specific binding sites (receptors) on the host cell. Small viruses enter host cell by endocytosis, shedding the capsid upon entry. Other viruses inject the genetic information into the cell leaving the capsid structure behind; permanently attached to the outside of the cell. Virus Slide # 7

8. Viruses: Hijacking a Living Cell for Reproduction. 1.Virus attaches to cell. 2.Virus injects genetic info into the host cell. 3.Host cell DNA is destroyed. 4.Cell machinery is forced to make virus genome and proteins. 5.Viruses are assembled. 6.Viruses break out of cell. *(Some viruses allow the cell to live as virus factories. Viruses bud out without destroying the cell. -ex. HIV) Slide # 8

9. Virus enzyme lyses the bacterium’s cell wall & releases new viral particles Viral proteins & nucleic acids assemble into complete virus particles Virus takes over cell’s metabolism, causes cell to make virus proteins and nucleic acids Virus injects nucleic acid into cell Virus attaches to cell wall Bacteriophage Bacteriophage DNA Bacteriophage protein Bacteriophage protein coat Bacteriophage DNA Bacterial chromosome Lytic Cycle Slide # 9 Viral Reproduction: The Lytic Cycle Go to Section:

10. Viral proteins and nucleic acids assemble into complete viral particles Viral enzyme lyses the bacterium’s cell wall, releases new viral particles Viral DNA inserts itself into bacterial chromosome Viral DNA (prophage) replicates with bacterium for many generations Viral DNA (prophage) can exit the bacterial chromosome Viral DNA forms plasmid Bacteriophage DNA Bacterial chromosome Virus injects nucleic acid into cell Prophage Lytic Cycle Lysogenic Cycle A Lysogenic Infection Go to Section: Slide # 10

11. AIDS Acquired Immune Deficiency Syndrome 1. The immune crippling disease caused by the HIV virus in which the body becomes unable to protect itself against any secondary infections. 2. HIV-Human Immunodeficiency Virus 3. HIV infects the immune system cell called Helper T cells (-most important white blood cell involved in identifying infections.) Slide # 11

12. Body Fluids with High Concentrations of HIV 1. Blood 2. Semen/Vaginal fluids (as high as blood) 3. Breast milk 4. Pus from sores Slide # 12

13. Low Concentrations of HIV It is highly unlikely you will be infected if you come into contact with: a.Sweat b.Tears c.Urine d.Saliva (-highly possible if blood from mouth sores is present) Slide # 13

14. How is HIV Spread? 1. ANY type of unprotected sexual activity (highest risk) 2. Sharing used drug needles 3. Pregnancy-from mother to child 4. Sharing razors- if blood is present 5. Kissing- if even the smallest amount of blood is present. (-membranes of mouth are thin enough for HIV to enter straight into the body.) 6. Tattoos /body piercing if equipment is not clean. Slide # 14

15. How is HIV not spread 1. Shaking hands 2. Hugging 3. Swimming pools 4. Toilet seats 5. Insect bites 6. Donating blood Slide # 15

16. Retrovirus 1. RNA virus that changes its RNA into DNA when inside the host cell. 2. Contains reverse transcriptase enzymes. 3. Example of a Retrovirus is HIV. Slide # 16

17. Reproduction of HIV

18. Can HIV be cured? 1. NO! Drugs are available to manage the disease, but HIV stays in the body forever! 2. PROBLEM: RNA viruses mutate at a very high rate. A person with HIV under control can evolve resistance to the drug treatments. 3. Some infected persons have several strains of HIV in their bodies.

19. Initial infection- flu-like symptoms a few weeks after infection. Stage 1:HIV positive with no symptoms- can stay at this stage for up to 10 years, but still can pass on the virus. Stage 2:HIV positive with symptoms- person is said to have AIDS. Symptoms include: –swollen glands, chronic diarrhea, loss of weight and appetite, fever, fatigue, skin rashes (lesions), night sweats, oral thrush. Life expectancy: 2 to 5 years. What does HIV look like?

20. Death and AIDS Stage III-Full blown AIDS- a.Person dies of rare opportunistic infections that take advantage the weakened immune system: b.Person dies in a matter of months. c.AIDS related illnesses include rare cancers and Pneumonia.

21. Example 1.HIV Virus attaches to host cell’s surface

22. 2. HIV seeks out the nucleus and injects its genetic information

23. 3. HIV directs the cell to make new HIV virus parts, which are then assembled.

24. 4. New HIV viruses break out of the cell, and spread to take over other host cells. The cell is destroyed (lysis) as a result.