Viruses

What is a virus? Virus: small, nonliving particle that invades and then reproduces inside a living cell Considered nonliving because viruses are not cells. They don’t use energy to grow or respond to their surroundings Only multiply when within a cell.

Host: living thing that provides a source of energy for a virus Parasite: organisms that live on or in a host and cause harm Viruses can infect organisms in all 6 kingdoms Viruses are named after the disease it causes or the organism they infect

The Shapes and Sizes Can be in all shapes and sizes Round, rod-shaped, bricklike, threadlike, bulletlike, robotlike Bacteriophage: virus that infects bacteria Vary in shape Smaller than cells and cannot be seen with our microscopes Smaller than bacteria cells Show page 48 in book then page 50

Structure of Viruses All viruses have two parts Outer coat that protects Inner coat made of genetic material Genetic material contains instructions for making new viruses Outer coat plays important role during invasion of a host cell Two parts like an m&m show page 50 How virus attaches to a host transparency pg 51

How viruses multiply After attaching it enters the cell Takes over the cell’s functions Directs to make more viruses Active viruses: immediately goes to action Makes copy after copy Hidden viruses: becomes part of the cell and waits to become active Transparencies of how viruses multiply pg 52 and 53

Caused by a virus Influenza-flu Rabies Chicken pox Polio Measle and mumps Thank goodness for vaccines!!

Review Explain why biologists consider viruses to be nonliving. What is the basic structure of a virus? Compare the two ways viruses can multiply.