1. Viruses
Chapter 7.1

2. POINT > Describe what a virus is
POINT > Describe virus structure
POINT > Define bacteriophage
POINT > Explain how viruses reproduce
POINT > Define two types of viruses
POINT > Discuss the prevention and treatment of viral diseases

3. Why care about viruses?
Influenza virus has killed over 100,000,000 people (40,000,000 in )
HIV virus (AIDS) has killed 35,000,000 in 35 years
Smallpox virus killed 300,000,000 in the 1900’s
What virus is coming next ??

4. POINT > Describe what a virus is
A virus is a nonliving particle that can invade a cell and reproduce
The cell that a virus invades is called the host cell
Viruses cannot reproduce by themselves
Viruses use the host cell to reproduce many more viruses

5. POINT > Describe what a virus is
Viruses are very small. Much smaller than any cells

6. CHECK:
Are viruses alive?
What do we call the cell that a virus invades?
Is a “carrier” homozygous or heterozygous?
What human disease is caused by one extra #21 chromosome?
What is one function of lipids?

7. POINT > Describe virus structure
Viruses can look different, but most viruses are made of two parts:
A protein coat (capsid) that protects the virus
Inside the coat is a nucleic acid (DNA or RNA)

8. POINT > Describe virus structure
The nucleic acid (DNA or RNA) contains the genetic information to make more virus particles

9. POINT > Define bacteriophage
Viruses attack and invade all organisms
Animals, plants, fungi and bacteria are all attacked by different types of viruses
The viruses that attack bacteria are called bacteriophages

10. POINT > Define bacteriophage
One type of virus only attacks one type of cell
Ex. A virus that attacks a plant does not attack animals or bacteria
Even viruses that attack humans, usually can only infect specific cell types
Ex. The HIV virus (that causes AIDS) only attacks human white blood cells

11. CHECK:
What are the two parts of a virus?
Do some viruses attack plants?
Can a virus that attacks a plant also attack you?
What is a bacteriophage?

12. POINT > Explain how viruses reproduce
1. The virus attaches to the host cell membrane

13. POINT > Explain how viruses reproduce
2. The virus injects nucleic acid into the host cell

14. POINT > Explain how viruses reproduce
3. The virus uses the cell’s organelles to make more virus particles inside the cell

15. POINT > Explain how viruses reproduce
4. The virus breaks the cell membrane, releasing the new viruses (3,000 to 100,000 new virus particles)

16. CHECK:
What is the first step in viral infection?
What is the second step in viral infection?
What is the third step in viral infection?
What is the fourth step in viral infection?

17. POINT > Explain how viruses reproduce
There are two main types of viruses
1. Active viruses: Reproduce and destroy the host cell very quickly (8-36 hours)
2. Hidden viruses: Virus DNA enters into host cell DNA and waits for days, months, even years before reproducing

18. POINT > Discuss the treatment and prevention of viral diseases
There are no effective medicines to treat viral infections. Nothing works well after the virus gets in
We use medicine to treat the symptoms and feel better, but the medicines don’t fight the virus
The best treatment is rest, lots of water and good nutrition

19. POINT > Discuss the treatment and prevention of viral diseases
We can prevent some viruses by using vaccines
A vaccine is a part of a virus that can’t make you sick
When we put a vaccine in our body, it prepares the body to fight the real virus
Vaccines have almost ended diseases like small pox and polio, both of which killed millions of people

20. POINT > Discuss the treatment and prevention of viral diseases
We can also prevent some viruses by washing our hands and not sharing food or eating utensils

21. CHECK:
What is one way to prevent getting a virus?
What is another way to prevent getting a virus?

22. Homework:
Read 7.1 pages
S.A. page 215 #1-4
GRAS pages (All)

23. Figure 6.18