1. Viruses
Something you don’t want to catch…

2. NO! 1.Viruses Made of cells Has a metabolism to grow and reproduce
How do scientists classify things as living?
Made of cells
Has a metabolism to grow and reproduce
Information stored in DNA
Are viruses alive?
NO!

3. 1. Viruses 3. What do viruses and living organisms have in common?
Both use nucleic acids to store genetic information in the form of DNA or RNA
Both change over time (evolve)

4. 1.Viruses
4. If viruses do not have their own metabolism to grow and reproduce, how do they survive?
By hijacking living cells and using their metabolism to grow and reproduce.

5. 2. Living or Nonliving? Characterisitic Viruses Bacteria Structure
Capsid, DNA, Envelope
DNA, Cell membrane, Cytoplasm
Reproduction
Growth
Obtains and Uses Energy?
 Response to Environment?
 Harms body by?
 Living?

6. 2. Living or Nonliving? Characterisitic Viruses Bacteria Structure
Capsid, DNA, Envelope
DNA, Cell membrane, Cytoplasm
Reproduction
 Host cell needed
Independent
Growth
Obtains and Uses Energy?
 Response to Environment?
 Harms body by?
 Living?

7. 2. Living or Nonliving? Characterisitic Viruses Bacteria Structure
Capsid, DNA, Envelope
DNA, Cell membrane, Cytoplasm
Reproduction
 Host cell needed
Independent
Growth
 No - assembled
 Yes
Obtains and Uses Energy?
 Response to Environment?
 Harms body by?
 Living?

8. 2. Living or Nonliving? Characterisitic Viruses Bacteria Structure
Capsid, DNA, Envelope
DNA, Cell membrane, Cytoplasm
Reproduction
 Host cell needed
Independent
Growth
 No - assembled
 Yes
Obtains and Uses Energy?
 No
Yes
 Response to Environment?
 Harms body by?
 Living?

9. 2. Living or Nonliving? Characterisitic Viruses Bacteria Structure
Capsid, DNA, Envelope
DNA, Cell membrane, Cytoplasm
Reproduction
 Host cell needed
Independent
Growth
 No - assembled
 Yes
Obtains and Uses Energy?
 No
Yes
 Response to Environment?
 Harms body by?
 Living?

10. 2. Living or Nonliving? Characterisitic Viruses Bacteria Structure
Capsid, DNA, Envelope
DNA, Cell membrane, Cytoplasm
Reproduction
 Host cell needed
Independent
Growth
 No - assembled
 Yes
Obtains and Uses Energy?
 No
Yes
 Response to Environment?
 Harms body by?
 Disrupting Homeostasis
Producing Toxins
 Living?

11. 2. Living or Nonliving? Characterisitic Viruses Bacteria Structure
Capsid, DNA, Envelope
DNA, Cell membrane, Cytoplasm
Reproduction
 Host cell needed
Independent
Growth
 No - assembled
 Yes
Obtains and Uses Energy?
 No
Yes
 Response to Environment?
 Harms body by?
 Disrupting Homeostasis
Producing Toxins
 Living?

12. 3. Virus Reproduction
First, the virus gains entry to the cell by connecting with cell receptors.
Second, the viruses’ DNA or RNA is injected into the cell.

13. 3.Virus Reproduction
c. Third, viral nucleic acid replicates and takes over the cell.

14. 3. Virus Reproduction d. Fourth, new viral particles are packaged
and released from
the cell.

15. 4. 2 types of viral infections
Lytic infection- a virus enters a cell, makes copies of itself, and causes cell to burst .
Lysogenic infection- a virus integrates its DNA into the DNA of the host cell, and the viral genetic information replicates along with the host cell’s DNA.

16. WHAT’S THE DIFFERENCE? Lytic vs. Lysogenic
c. Viruses with lysogenic reproduction, lay dormant until the cell is replicated during mitosis.
Lytic vs. Lysogenic
WHAT’S THE DIFFERENCE?

17. 2 Types of Viral Infection
Lytic - influenza
Lysogenic - herpes

18. CHECK POINT
Lytic
Lysogenic
Lytic vs. Lysogenic

19. 5. Virus Types Bacteriophages = are viruses that attack bacteria
Retroviruses = viruses that use RNA to reverse transcribe DNA that integrates into the host genome.
Example: HIV

20. 6. How do you treat a virus?
Remember you cannot treat a viral infection but you can prevent one by getting a vaccine.
Viruses must be prevented.
Wash your hands
Do not share drinks, food, etc.
Practice good hygeine

21. 6.Vaccine
A vaccine improves
immunity to a particular disease.

22. 6. How do vaccines work?
A vaccine contains a weakened strain of the microbe.
When injected into your body it stimulates your immune system to recognize it as foreign, destroy it, and remember it.
So if your body encounters the full strain later, it can easily recognize and destroy it!!!!!

23. Important facts about viruses
SUMMARY
Important facts about viruses
Viruses must be produced within living cells
Viruses destroy the living cells they grow in
Viruses gain entry by specific receptors on the host cell