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.

Release

Attachment

Step 1

Step 2 ReplicationAssembly

LYTIC CYCLES

Step 3

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?

AIRFOOD /WATERSEXUALLY TRANSMITTEDSOIL

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

INFLUENZA

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