agenda: activity: brain pop notes: discovery of viruses activity: lytic vs. lysogenic video...
TRANSCRIPT
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
Monday 4/13/2015
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
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.”
Virus Terminology1. Virus: Segments of nucleic acids held in a protein coat.
Are NOT cells; not living, do not grow, no metabolism.2. Pathogen: agents that cause disease(s)3. 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.
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)
Structure of Viruses1. 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.
Viral Reproduction• There are 2 pathways a virus can take in order to replicate itself; Lytic Cycle or Lysogenic Cycle
1. Lytic CycleStep 1: Virus attaches to cell, injecting its DNA
Step 2: Viral genes enters the cellStep 3: Host cell replicates viral genes & viral proteins
(A.K.A. Capsid Proteins)Step 4: Proteins assemble to form a complete virusStep 5: Host cell bursts open, releasing a NEW virus
Lytic Cycle
2. Lysogenic CycleSome 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 cycleExample: 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
Lysogenic CycleStep 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*
Lysogenic Cycle
Lytic VS Lysogenic Cycle: Video• http://www.youtube.com/watch?v=_J9-xKitsd0