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Monday 4/13/2015 Virus & Bacteria Agenda: Activity: Brain Pop

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Presentation on theme: "Monday 4/13/2015 Virus & Bacteria Agenda: Activity: Brain Pop"— Presentation transcript:

1 Monday 4/13/2015 Virus & Bacteria Agenda: Activity: Brain Pop
Notes: Discovery of Viruses Activity: Lytic vs. Lysogenic Video Homework: Viral Reproduction Worksheet due Tuesday/Wednesday 4/14- 4/15/2015 for 40 Points

2 Week Schedule Tuesday 4/14/2015 is a 1,3,5 Block day with lunch at 10:30 ON CAMPUS Wednesday 4/15/2015 is a 2,4,6 Block day with lunch at 10:30 ON CAMPUS Thursday and Friday are block days (1,3,5 and 2,4,6 Friday

3 Discovery of Viruses At the end of the 19th century, scientists began researching the cause of Tobacco Mosaic Disease: stunts the growth of tobacco plants. Scientists filtered bacteria from the sap of infected tobacco plants. FINDING: Filtered sap could still cause uninfected plants to become infected. CONCLUSION: The pathogen is smaller than a bacterium; the pathogen was called a virus- Latin word meaning “poison.”

4 Virus Terminology Virus: Segments of nucleic acids held in a protein coat. Are NOT cells; not living, do not grow, no metabolism. Pathogen: agents that cause disease(s) Bacteriophage: Viruses that infect bacteria, complex structure. 4. Capsid: Protein coat of a virus; contains DNA or RNA, NOT BOTH! 5. Envelope (Membrane): Surrounds the capsid, allows the virus to enter the cell. Made up of proteins, lipids and glycoproteins. Glycoproteins: proteins that attach carbohydrate molecules.


6 Are Viruses alive? All living things are made up of cells; cells can grow and reproduce; the smallest organism with “cell-like” properties are prokaryotes. Viruses are NOT cells, viruses are smaller than prokaryotes. Viruses are pathogens; they CAUSE disease. How Virus Replicates: Infect cell(s), use the cell to make more viruses. Viruses need cells because they do not have the properties needed to produce life. (Don’t grow, metabolize and no homeostasis)

7 Structure of Viruses 1. Filaments- Long rods. Example: Ebola virus 2. Spherical- Studded with receptors, allowing the virus to enter the cell. Example: Influenza virus 3. Helical- Rod-like in appearance with capsid proteins winding around the core in a spiral. 4. Polyhedral- Has MANY sides; the capsid of most polyhedral viruses have 20 triangular faces & 12 corners.

8 Viral Reproduction There are 2 pathways a virus can take in order to replicate itself; Lytic Cycle or Lysogenic Cycle 1. Lytic Cycle Step 1: Virus attaches to cell, injecting its DNA Step 2: Viral genes enters the cell Step 3: Host cell replicates viral genes & viral proteins (A.K.A. Capsid Proteins) Step 4: Proteins assemble to form a complete virus Step 5: Host cell bursts open, releasing a NEW virus

9 Lytic Cycle

10 2. Lysogenic Cycle Some viruses stay inside a cell, spreading its virus through a cells natural reproduction Lysogenic cycle allows the viral genes to replicate without destroying the host cell. In some lysogenic viruses, environmental changes can cause the lysogenic cycle to begin. A virus in the lysogenic cycle can switch to the lytic cycle Example: Cold sore virus; virus hides in facial nerves. When body conditions are favorable (ie. stress), the virus will cause tissue damage resulting in a cold sore or fever blister

11 Lysogenic Cycle Step 1: Viral gene is inserted into host chromosome Step 2: Viral genes (DNA or RNA) combines with host DNA Step 3: Host cell divides normally, resulting in 2 new cells, each containing viral DNA. *NO damage to the host cell* * The new cells, containing viral genes, can switch to the Lytic Cycle to create MORE viruses*

12 Lysogenic Cycle


14 Lytic VS Lysogenic Cycle: Video

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