Viruses

Viral structure Viruses are not cells. Viruses are not considered living. (cannot reproduce by themselves- must use a HOST) Basic structure: Protein coat-CAPSULE or CAPSID Nucleic acid core (RNA or DNA) -ENVELOPE- outside protein coat in some viruses

HIV VIRUS

Virus Categories DNA viruses – stable, do not mutate rapidly Single-stranded or double-stranded Smallpox, Hepatitis B RNA viruses – mutate rapidly, unstable HIV, Rhinovirus

has a shape that matches a molecule in the plasma membrane Viruses are host specific – a protein on the surface of the virus (GLYCOPROTEIN) has a shape that matches a molecule in the plasma membrane of its host, allowing the virus to lock onto the host cell.

LYTIC CYCLES Attachment Step 1 Step 3 Release Assembly Step 2 Replication

Lytic Cycle (VIRULENT- or fast acting) STEP 1-Virus attaches to host cell’s membrane and injects its nucleic acid into the host cell. STEP 2- The viral nucleic acid takes over protein synthesis, creating new viruses. (can infect DNA or go straight to the ribosomes) STEP 3- The host cell bursts, LYSES, releasing the newly formed viruses.

The Lysogenic Cycle

LYSOGENIC CYCLE- TEMPERATE VIRUS or slow acting STEP 1-Virus attaches to host cell’s membrane and injects its nucleic acid into the host cell. STEP 2- Virus cuts into DNA and becomes part of the cell STEP 3- When cell reproduces so does the virus (DORMANCY)- STEP 4- LYTIC STAGE when stimulus is right

How are viruses spread? AIR FOOD /WATER SEXUALLY TRANSMITTED SOIL

KINDS OF VIRUSES VIRUS Infected cells HERPES NERVE CELLS HIV T – HELPER CELLS (WHITE BLOOD CELLS) EBOLA LINING OF THE BLOOD VESSELS (INTESTINES) HUMANPAPILLOMAVIRUS (WARTS) SKIN MEASLES DERMIS OF SKIN WEST NILE LYMPH NODES- NERVES RABIES BRAIN- NERVES CHICKEN POX / SMALL POX PNEUMONIA LUNGS INFLUENZA