1. Viruses Doesn’t belong to any kingdom -It’s not a plant or an animal.
-It’s not a fungi, protist, or bacteria.
WHAT IS A VIRUS?

2. What are Viruses?
Viruses are made up of nucleic acids (RNA or DNA), a protein coat, and in some cases, a lipid envelope surrounds the protein.
Viruses with RNA that transcribe into DNA are called retroviruses
Considered non-living structures
Capable of reproducing only inside a host cell.
Viruses are specific to the type of cells they infect (species specific)
Bacteriophage—viruses that infect bacteria

3. Are Viruses living or non-living?
They are not considered living, but do have some characteristics of life.
Figure Viruses and Cells
Section 19-2

4. Viruses have no nucleus, no organelles, no cytoplasm or cell membrane—Non-cellularvs

5. 2. Flu (influenza), HIV 1. Bacteriophage
A virus is an infectious agent made up of nucleic acid (DNA or RNA) wrapped in a protein coat called a capsid.
Capsid (protein coat)
inside contains either
RNA or DNA
2. Flu (influenza), HIV
DNA or RNA
1. Bacteriophage
Surface Marker
Capsid (protein coat)

6. Size of Viruses
Viruses are smaller than even the smallest cell.

7. Surface Markers Receptor Sites Virus Cell
A virus recognizes cells it can infect by matching its surface marker with a receptor site on a cell.
Certain viruses can only attack certain cell types. They are said to be specific.
Surface Markers
Receptor Sites
Virus
Cell
It’s like the pieces of a puzzle. The ends have to match up so only certain pieces fit.

8. Viruses REPLICATE: Organisms REPRODUCE
Organisms, including bacteria, reproduce by either sexual or asexual means.
Viruses require a host cell to replicate, it must invade a host cell and take over the cell activities, eventually causing destruction of the cell and killing it. Replication is how the virus spreads.
Two processes of replication:
Lytic Cycle ( common cold, flu, etc)
Lysogenic Cycle ( shingles, AIDS) – can stay in a “dormant” stage for years before becoming active
Video: How a Virus invades your body

9. Lytic Cycle Virus attaches to cell.
The virus enters a cell, makes copies of itself and causes the cell to burst releasing more viruses.
DNA/RNA injected into cell.
DNA/RNA is copied.
Virus copies itself.
Cell bursts (lyses/dies) and releases new viruses.

10. Lysogenic Cycle The virus binds to bacteria (host)
In the lysogenic phase the viral DNA is integrated into the host’s DNA   The virus can stay inactive or a period of time, then become active and switch to a lytic lifestyle.
The virus inserts its DNA into the bacteria
The viral DNA gets incorporated into the cell's chromosome
Viral DNA is replicated along with the host’s cell’s DNA
Stays dormant or can enter the lytic cycle
Prophage – when the viral DNA is embedded in the host DNA

11. The Lytic and Lysogenic Cycles
Figure 13.12

12. Discuss Q: How do we treat viruses? Q: How can we prevent viruses?
Antivirals – They are virus specific. Work by stopping viruses from binding to cells, or stop DNA coding.
Supportive care – rest, fluids, fever/pain reducer, time
NO ANTIBIOTICS!!
Wash hands
Wash food before eating
Careful food storage and preparation
Clean water
Stay Healthy
Clean cuts and wounds
Sterile practices
Vaccines
Education
If there are antivirals available, how come they are not used more often:
Antiviral such as Tamiflu, can be associated with a host of adverse effects including nausea, vomiting, diarrhea, headache, and abdominal pain. It only reduces the duration of a virus by 21 hours.

13. What happens if you are vaccinated?
Your body will recognize the virus immediately and already has the weapons (antibodies) to fight it off.
Antibodies are specific for a single virus or bacteria
Antibodies bind to the specific virus or bacteria to stop it from infecting you

14. Create a Venn Diagram Compare and Contrast Viruses and Bacteria
Include: size, structure, treatment /prevention, living/non-living
Viruses
Bacteria