Transcript Ch. 7 Viruses

Ch. 7
Viruses
Key Terms
1.
2.
3.
4.
5.
Virus
Host
Parasite
Bacteriophage
Vaccine
What is a Virus
• Virus is a tiny, nonliving particle that invades
and then multiplies inside a living cell.
• Viruses are not cells.
• The only way in which viruses are like
organisms is that they can multiply.
• They can only multiply when they are inside a
living cell.
What is a Virus
• The organism that a virus multiplies inside is
called a host.
• A host is a living thing that provides a source
of energy for a virus or an organism.
• Viruses act like parasites. (organisms that live
on or in a host and cause it harm).
Structure of Viruses
• Viruses are smaller than cells and vary in size
and shape.
• Some are round
• Others are shaped liked rods, brinks, threads,
or bullets.
Bacteriophage “bacteria eater”: is a virus that
infects bacteria.
Structure of Viruses
• All viruses have two basic parts: a protein coat that
protects the virus and an inner core made of genetic
material.
• Surface proteins play a huge role in the invasion of a
cell.
• Shape allows it to attach to certain cells in the host.
• Most can only attach to a certain type of cell. (lock
and key type situation)
• A cold virus can only attach to cells in the nose and
throat.
How viruses multiply
• Once inside a cell, a virus’s genetic material
takes over many of the cell’s functions.
• It instructs the cell to produce the virus’s
proteins and genetic material.
• These proteins and genetic material then
assemble into new viruses.
• Some viruses take over cell functions
immediately, others wait for awhile.
Active Viruses
• After entering a cell, an active virus goes into
action immediately.
• It’s genetic material takes over and quickly
begins to produce the virus’s proteins and
genetic material.
• New viruses are made. (photocopy)
• Once the invaded cell is full of viruses it burst
open and releases hundreds of new viruses as
it dies.
Hidden Viruses
• Some viruses are hidden inside of the cell and are
not active. (Sometimes for very long periods of time).
• Certain conditions can cause the virus to become
active.
• A cold sore is an example.
• Sunlight or stress can cause people to develop cold
sores.
• Where in a host cell does a hidden virus “hide” while
it is inactive? Genetic Material
Viral Diseases
 Viruses can cause diseases. (Cold, flue, AIDS, etc)
 They can spread in various ways. (contact with
contaminated objects, a bite from an infected animal)
 Treatment for viral diseases. (no cures for them)
 Medicine can relieve the symptoms of a viral infection.
 Resting, drinking plenty of fluids, and eating well
balanced meals can help you recover from a viral
disease.
 Vaccines are used to prevent diseases.