Viruses Viral structure Viruses are not cells Viruses

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 – Single-stranded or double-stranded – HIV, Rhinovirus

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 WEST NILE RABIES CHICKEN POX / SMALL POX PNEUMONIA

• HIV is a retrovirus injecting the enzyme, reverse transcriptase into the cell to copy viral RNA into DNA.