1. Page 21 EQ: How do Viruses compare to cells? How do viruses replicate?

3. Virus Facts
Structure that contains strands of genetic material (DNA or RNA) surrounded by a protective protein coat
Cannot live independently outside of a host cell
Does not grow
Does not have ANY organelles!
Does not have a cell membrane
NOT a cell or made of cells!
NONLIVING

4. Virus Structure
If a virus’ genetic material is RNA, the virus is called a retrovirus.
The capsid helps the virus attach to the host cell & protects the virus.

5. Virus size compared to cells

6. Viruses and cells Alike Different Reproduce
Have DNA (Although some viruses do NOT have DNA)
Can change over time (evolve)
Have protein
Cells can reproduce independently & viruses need a host
Only cells grow
Only cells need energy
Only cells can respond to changes in their environment
Cells are living & viruses are not

7. Virus Reproduction – pg. 25

8. Lytic Cycle
This cycle occurs when the virus enters the cell and immediately begins replicating.
Results in the (relatively) quick death of the host cell.
Symptoms appear in 1-5 days usually.
Lytic = Quick!

9. Lytic
Cycle

10. Lysogenic Cycle
This cycle occurs when the virus enters the cell and integrates its DNA into the host cell’s DNA.
No virus particles are produced by the cell.
No virus = no symptoms

11. Lysogenic
Cycle

13. How Vaccines Work

14. Treating Viruses Antibiotics work on bacteria – NOT viruses!
To prevent a virus from making you sick, you should get a vaccine.
A vaccine is a weakened/inactive virus that is injected into you. It works by stimulating your immune system to fight the pathogen.
Your immune system also “learns” to recognize the pathogen. When you really encounter the virus, your immune system quickly knows that it is a bad thing that needs to be destroyed so you don’t get sick.
Vaccines give you immunity to the virus. The only other way you can be immune is if you actually have the disease.
To treat a viral infection, you really just treat the symptoms (meds to reduce fever, rest, drink fluids) while your immune system does it’s thing.