Download VIRUSES - Piscataway Township Schools

VIRUSES: Alive or Not?
RECALL: The SIX
Characteristics of Life
• Made up of cells
• Made up of similar
chemicals
• Uses energy
• Grows and develops
• Responds to the world
around them
• Reproduces
WHAT IS A VIRUS?
The common cold
virus - Rhinovirus
• Virus: small, nonliving
particle that invades
and then multiplies
inside a living cell.
– Do not use energy
to grow or to
respond to their
surroundings
– Cannot make food,
take in food, or
produce wastes
Virus Shapes and Sizes
• Vary in shape and size
–
–
–
–
Round
Rod-like
Robot-like
Brick shaped
• Although they vary in
size, all viruses are
extremely tiny. The
largest virus is no
more than 250 nm
long.
• What’s a nanometer?
Virus Structure
1. Protein Coat
- each virus has
unique proteins on
its coat, the shape
of the proteins
determine which
cells it will attack.
2. Genetic Material
- Either DNA or
RNA
Viruses Can Only Multiply
When They are Inside a
Living Cell
• Viruses act like
a parasite
because they
destroy the
host cells they
take over when
they multiply.
Two Types of Viruses
• Once a virus enters the cell it takes over the
cell’s functions.
• Some viruses take over right away, others
wait a while.
– Active virus
– Hidden virus
Examples of each kind:
Hidden – HIV, herpes
Active – Rhinovirus, Influenza, Chicken pox
How Do Viruses Multiply?
STEP ONE:
ABSORPTION
The virus attaches
itself to the cell
membrane
How Do Viruses Multiply?
STEP TWO:
ENTRY
The virus injects
its genetic
material.
How Do Viruses Multiply?
STEP THREE:
REPLICATION
The cell starts to
produce the virus’s
proteins and
genetic material.
How Do Viruses Multiply?
STEP FOUR:
ASSEMBLY
New viruses
assemble.
How Do Viruses Multiply?
STEP FIVE:
RELEASE
The cell bursts
open releasing
new viruses.
Hidden Viruses Multiply
Differently
• The only difference is that the hidden virus’
genetic material becomes a part of the
organism for a while until it becomes active.
• See the difference here.
• Cep-1021
REMEMBER THE STEPS
• ABSORPTION
• ENTRY
• REPLICATION
• ASSEMBLY
• RELEASE
Viral Diseases
1. Can cause some short-term
sickness (Ex. Common cold)
2. Can cause death (Ex. AIDS)
3. Spread through physical
contact or inhaled droplets
4. NO medications to cure
viruses.
-
medicines can treat the
symptoms
Our immune system (white blood
cells) is our first defense
Preventing Viruses
Vaccines: substance
that stimulates the
body to produce
chemicals that
destroy viruses or
bacteria.
- may be dead or
altered viruses
- they activate the
body’s natural
defenses
How are Antibiotics and
Vaccines Different?
ANTIBIOTICS
A chemical
used to kill or
slow the
growth of
bacteria
VACCINES
Virus introduced into
the body in order to
put the body “on
alert.” If the virus
ever infects the body,
the immune system
recognizes it and
destroys it.
Why get a Vaccine?
– How are vaccines beneficial?
– Besides vaccines, what other
methods should be used to help
prevent disease?
– Why do people still get the flu even
though they’ve gotten the flu shot?
– Why not just get a SUPER Flu shot
that covers them all?
EXAMPLES OF VIRUSES
• Polio
• Small pox
• Human
Papillomavirus
• AIDS
• Influenza
• Herpes
How Viruses Effect Humans
• HPV
• More than 100
different strands
• Transmitted by direct
contact
• Symptoms: Warts or
none
• Very extreme case:
– Tree man
Measles – A Case Study
• Symptoms: Measles symptoms usually show up in two stages.
– Stage 1: runny nose, cough, and a slight fever. As the infection progresses, the
person's eyes become red and sensitive to light, and the fever rises.
– Stage 2 (3-7 days later) The fever reaches 103oF-105oF, and a red blotchy rash
appears. The rash usually starts on the face and then spreads to the chest, back,
and arms and legs,.The rash lasts for 4 to 7 days. Small white spots might also
appear on the gums and inside of the cheeks.
• Measles is very contagious. An uninfected person can get measles
simply by breathing the air in a room where an infected person has
been.
– The virus can live in the air for 2 hours after an infected person leaves a room.
Infected persons are usually infectious to others even before symptoms appear.
(hidden virus)
• Complications: Pneumonia occurs in up to 6 percent of reported
measles cases and accounts for 60 percent of deaths from measles.
Encephalitis (inflammation of the brain) can also occur.
– Infants under age 2 years and adults over age 20 have a greater risk of
complications.
• Prevention: Get vaccinated!
–
Not so easy for some.