Viruses AKA the things that make us sick!

The Virus Viruses are tiny, non-living particles (NOT cells!) that infect living cells Cannot reproduce on their own Do not grow or develop Do not use energy

Parts of a Virus Protein shell called a capsid genetic material (DNA or RNA) Envelope made of stolen cell membrane Glycoproteins that attach to cells (handshake)

Parts of a Virus The virus we looked at yesterday is called a bacteriophage It has the same structural characteristics, but different names

Different Forms of Viruses

Viral Replication Viruses confuse cells, turning them into virus factories: Virus finds and attaches to a cell by matching glycoprotein receptors (handshake) DNA or RNA from virus enters the cell

Viral Replication Viral DNA or RNA is copied many times; cell is fooled into reading these new instructions New viral structures are manufactured New viruses burst out of the cell, killing it

Two Types of Viral Infection Lytic Infection – virus enters a cell and quickly makes copies, causing lysis of the cell Lysogenic Infection – a virus “hides” its DNA inside a host cell and lies dormant Viral DNA is copied each time the cell divides Will eventually turn lytic

The handshakes have to match! Viral Specificity Viruses are very specific – infect only certain cells Ex: cold virus infects respiratory cells The handshakes have to match!

lytic! Example 1 - Influenza Attacks and kills respiratory cells, causing flu symptoms Spreads fast, is copied quickly – lytic!

Example 2 - HIV Lysogenic! Human Immunodeficiency Virus attacks and kills cells of the immune system Takes years to actually cause illness – Death of immune cells leads to AIDS (acquired immune deficiency syndrome) Lysogenic! Video

Vaccines Vaccines are used to give immunity against viral infection Contain damaged/weakened form of a virus The immune system can then recognize and destroy the real virus if it ever enters the body There is no scientific evidence whatsoever that autism is linked to vaccination!