Viruses a Pre-Lesson
Viruses—a Pre-Lesson (Ch. 18 Sections 1,2,3)
Questions to ponder…
Which properties of life, as discussed in chapter 1, does a virus lack?
How are viruses similar to cells?
Why must viruses rely on living cells for replication?
What relationships exist between a virus and a pathogen?
What effect does a fever have on a virus?
How do viruses harm our cells?
Review of Cells
· Cells are the basic units of life.
· Organisms made of one or more cells illustrate all of the properties of life at some point in their life cycle.
· These properties of life include:
o Cellular organization
o Reproduction
o Metabolism
o Homeostasis
o Heredity
o Responsiveness
o Growth and development
Viruses
· Viruses are currently considered to be nonliving because they do not have all of the characteristics of life because they…
o do NOT grow
o do NOT maintain homeostasis
o do NOT metabolize
o can only reproduce inside of a host cell
· Viruses are similar to cells in that they…
o have genetic material, either DNA or RNA
o have proteins
o have receptor/marker molecules on the outside for communication/recognition
Make a Venn diagram of Viruses and Cells
· Other Information on Viruses
o Viruses are pathogens. What is a pathogen?
o Viruses consist of two parts: Nucleic acid (DNA or RNA) and a protein coat, called a capsid.
§ The protein coat can be studded with receptors, such as glycoproteins in HIV, that allow it to bond to complementary receptors on certain cells to allow it’s nucleic acid to enter to start viral replication.
o Viruses basically “hijack” the cell and use it to manufacture more viruses. This is not what harms our cells, though, it is when the viruses lyse (burst) the cell upon exiting to go infect other cells. This destroys our cells and causes our symptoms to develop.
o Diseases/infections viruses cause (not a complete list)
§ Common cold
§ Flu
§ AIDS
§ Mononucleosis
§ Small pox
§ Chicken pox
§ Rabies
§ Warts
o Can antibiotic medications be used to get rid of a virus?
o What can you do to prevent or treat viruses?
§ Vaccines are substances produced from “killed” or weakened pathogens that can be used to prevent certain viruses.
§ Once you have a virus you can only treat the symptoms (fever, headache, congestion, etc.).
§ However, it is best to not always immediately treat a mild fever since a fever actually slows down the viral reproduction process allowing your body’s immune system to fight it faster.
o Viruses can lead to cancer when they affect genes on chromosomes that regulate the cell cycle. Ex. Human papilloma virus causes one type of cervical cancer.
Read and take notes over Ch. 18 Sections 1,2,3—optional, but recommended
View the United Streaming/Discovery Education Video: Life Science: Viruses (20 min)—optional
Go to Mrs. Roy’s website: www.kroymbhs.pbworks.com Click on PreAP Biology, then click on Websites. Click the link to Discovery Education and enter the passcode to set up a student account, then search for Life Science: Viruses Video.