VIRUSESChapter 7 Section 1

Characteristics of Viruses

● Tiny (smaller than cells)● Non living ● Enters a living cell and reproduces● No organisms are safe● Can multiply only when inside a living cell

HOST

● Organism that a virus enters and multiplies in

● Provides a source of energy for a virus or another organism

PARASITE

● Organism that lives on or in a host● Causes harm to its host● Destroys the cells in which they multiply

VIRUS SHAPES

● Round● Rod-shaped● Bricks ● Threads● Bullets● Robot Shape (Bacteriophage)

STRUCTURE OF VIRUSES

● Two basic parts● Protein Coat-protects virus ● Inner Core -made of genetic material

PROTEINS● Play an important role during invasion of

host● Allows the virus to attach to certain cells● Fit only into certain locks on the surface of

host● Allows certain viruses to only attach to

certain cells.

How Viruses Multiply

● Attaches to host● Enters cell● Genetic material takes over cell functions● Instructs cell to produce ● Sometimes happens immediately● Sometimes takes a while

ACTIVE VIRUSES

● Immediately goes into action● Cell quickly begins to produce protein and

genetic material● Like a photocopy machine left in on position● Makes copy after copy until host cell is full

HIDDEN VIRUSES

● Do not immediately become active ● Hide for a while● Does not affect the cells functions ● Can stay inactive for years● As host cell divides the genetic material of

virus is copied as well● Under certain conditions becomes active● Example: Cold Sore

Viruses & Disease

● Some like colds are short lived.● Other like AIDS have much more serious● Can cause disease in Trees, Pets

Usefulness of Viruses

● Gene therapy- use virus as messenger to give cells what they need

● Shows promise in disorders like cystic fibrosis where patience lack genetic material they need to keep lungs functioning properly. Gene therapy delivers genetic material needed by the lungs.