Viruses Chapter 7.1

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

Why care about viruses? Influenza virus 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 ??

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

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

CHECK: Are viruses alive? What do we call the cell a virus invades?

POINT > Describe virus structure Viruses can look different, but most viruses are made of two parts: 1.A protein coat (capsid) that protects the virus 2.Inside the coat is a nucleic acid (DNA or RNA)

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

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

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

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

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

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

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

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

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?

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

POINT > Discuss the treatment and prevention of viral diseases There are few effective medicines to treat viral infections. Nothing works very well We use medicine to treat the symptoms and feel better, but they don’t fight the virus The best treatment is rest, lots of water and good nutrition

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

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

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

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

Figure 6.18