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Viruses & Disease Chapter 19 Herpes virus Virus- Latin for poison Slide # 2 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! Protein coat Nucleic acid Tail Tail Fibers A virus depends upon a living cell for its existence, harming that organism in the process. Parasites Slide # 3 Relative Sizes of Viruses Slide # 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. Bacteriophage: a virus that infects a bacterium. Slide # 5 TAKS Practice One characteristic shared by a virus and a living cell is that both — F store genetic information in nucleic acids Cells & viruses DO G have a crystalline structure Cells don’t have this H gain energy directly from the sun Autotrophs / producers J use glucose for respiration Cells do this Correct answer: F Slide # 6 E. coli Infected with a Bacteriophage Bacteriophage E. coli What it looks like in real life. Bacteria are destroyed as viruses are released. Slide # 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. Virus Other viruses inject the genetic information into the cell leaving the capsid structure behind; permanently attached to the outside of the cell. Slide # 8 Viruses: Hijacking a Living Cell for Reproduction. 1. 2. 3. 4. Virus attaches to cell. Virus injects genetic info into the host cell. Host cell DNA is destroyed. 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 # 9 Viral Reproduction: The Lytic Cycle Bacteriophage protein coat Bacteriophage DNA Bacterial chromosome Virus attaches to cell wall Virus enzyme lyses the bacterium’s cell wall & releases new viral particles Lytic Cycle Virus injects nucleic acid into cell Viral proteins & nucleic acids assemble into complete virus particles Go to Section: Virus takes over cell’s metabolism, causes cell to make virus proteins and nucleic acids Bacteriophage Bacteriophage DNA Bacteriophage protein A Lysogenic Infection Slide # 10 Bacterial chromosome Bacteriophage DNA Virus injects nucleic acid into cell Lytic Cycle Viral enzyme lyses the bacterium’s cell wall, releases new viral particles Lysogenic Cycle Viral DNA forms plasmid Viral proteins and nucleic acids assemble into complete viral particles Go to Section: Viral DNA (prophage) can exit the bacterial chromosome Prophage Viral DNA (prophage) replicates with bacterium for many generations Viral DNA inserts itself into bacterial chromosome AIDS Acquired Immune Deficiency Syndrome Slide # 11 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 # 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 # 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 # 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 # 15 How is HIV not spread 1. Shaking hands 2. Hugging 3. Swimming pools 4. Toilet seats 5. Insect bites 6. Donating blood Slide # 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 . Reproduction of HIV 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. What does HIV look like? 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. Death and AIDS Stage III-Full blown AIDSa. 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. 1. HIV Virus attaches to host cell’s surface Example 2. HIV seeks out the nucleus and injects its genetic information 3. HIV directs the cell to make new HIV virus parts, which are then assembled. 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.