4C Viruses

NONLIVING Contain either DNA or RNA (but NEVER Both) VIRUS

Why is a virus considered non-living? They cannot replicate on their own (without a host cell) They cannot obtain and use energy They cannot respond to the environment

What a virus does It invades a cell. It turns the cell into a virus making factory until it no longer needs the cell. It then destroys the cell releasing new viruses to continue the cycle.

How does a virus replicate? Virus injects it’s genetic info into a host cell. Host cell then “replicates” viral DNA to makes new viruses

How do they replicate? (replicate means to make more) LYTIC CYCLE

Lysogenic Cycle Wait for animation

LYTIC CYCLE destroys host cell in a short amount of time LYSOGENIC CYCLE takes longer to destroy host cell

Both Cycles Together

Types of Viruses Adenovirus Retrovirus Bacteriophage

Adenovirus any of a group of DNA viruses first discovered in adenoid tissue, most of which cause respiratory diseases

Retroviruses Made of RNA Inject their RNA into the host cell Host cell makes it into DNA Viral DNA joins the host DNA Viral DNA pirates the cell and forces the cell to make new viral RNA and new viruses HIV is a retrovirus---good for students to know HIV is a retrovirus

Virus that attacks bacteria Bacteriophage Virus that attacks bacteria

Common Viral Diseases Rhinoviruses cause the common cold HPV (Human papillomavirus) can cause cervical cancer in women Herpes simplex viruses cause mouth and/or genital sores, lesions, and ulcers. Influenza viruses cause the flu HIV (Human Immunodeficiency Virus) causes AIDS and weakens the immune system Students should be familiar with these but do not need to memorize.

Rabies

H1N1

Plant Viruses

How is a disease caused by a virus? New viruses made inside BURST out of and destroy host cell When your cells die your health is affected

HIV attacks helper T cells. Most people that die who have AIDS do not die because of the virus, but because the virus weakens the immune system and leaves them susceptible to other sicknesses.

Controlling Viruses Antibiotics DO NOT work on viruses. Most human viral infections can be fought off by the immune system—boost the immune system with lots of water and rest.

How does a VACCINE work? Vaccines stimulate the immune system to create antibodies that recognize a certain virus… Vaccines inject a small amount of the virus into your system.

How do vaccines work? The body then builds antibodies to fight that specific virus. Antibodies remember that virus in the future in case you are exposed to that virus again. These antibodies patrol your body and if they recognize that virus…they call in reinforcements and your immune system goes to battle!

Compare viruses to living cells What do they have in common? They have DNA & RNA and They both change over time