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Viruses & Disease
Chapter 19
Herpes virus
Virus- Latin for poison
Slide # 2
1. A virus is a non-living particle
made up of
a. genetic material (DNA or
RNA; NOT both)
b. protein coat (capsid)
2. Can invade living cells.
3. Reproduce inside living cells.
4. Viruses ARE NOT CELLS!
Protein
coat
Nucleic
acid
Tail
Tail Fibers
A virus depends upon a living cell for its existence,
harming that organism in the process. Parasites
Slide # 3
Relative Sizes of Viruses
Slide # 4
The Structure Of a Virus
1. Viruses are made of a
core of DNA or RNA
surrounded by a
protein coat (capsid)
2. The Nucleic core is
either made up of DNA
or RNA but NOT both.
Bacteriophage: a virus that
infects a bacterium.
Slide # 5
TAKS Practice
One characteristic shared by a virus and a living cell is
that both —
F store genetic information in nucleic acids Cells & viruses DO
G have a crystalline structure Cells don’t have this
H gain energy directly from the sun Autotrophs / producers
J use glucose for respiration Cells do this
Correct answer: F
Slide # 6
E. coli Infected with a Bacteriophage
Bacteriophage
E. coli
What it looks like in real life. Bacteria are destroyed as viruses are released.
Slide # 7
How Viruses Infect a Host Cell
A virus is specific in the type of cell it invades. Proteins on
the virus capsid attach to specific binding sites (receptors)
on the host cell. Small viruses enter host cell by endocytosis,
shedding the capsid upon entry.
Virus
Other viruses inject the genetic information into the cell
leaving the capsid structure behind; permanently attached to
the outside of the cell.
Slide # 8
Viruses: Hijacking a Living Cell for Reproduction.
1.
2.
3.
4.
Virus attaches to cell.
Virus injects genetic info into the host cell.
Host cell DNA is destroyed.
Cell machinery is forced to make virus genome
and proteins.
5. Viruses are assembled.
6. Viruses break out of cell.
*(Some viruses allow the cell to live as virus
factories. Viruses bud out without destroying the
cell. -ex. HIV)
Slide # 9
Viral Reproduction: The Lytic Cycle
Bacteriophage
protein coat
Bacteriophage DNA
Bacterial
chromosome
Virus attaches to cell wall
Virus enzyme lyses the
bacterium’s cell wall & releases
new viral particles
Lytic Cycle
Virus injects nucleic
acid into cell
Viral proteins & nucleic
acids assemble into
complete virus particles
Go to
Section:
Virus takes over cell’s
metabolism, causes cell to
make virus proteins and
nucleic acids
Bacteriophage
Bacteriophage DNA
Bacteriophage protein
A Lysogenic Infection
Slide # 10
Bacterial
chromosome
Bacteriophage
DNA
Virus injects nucleic
acid into cell
Lytic
Cycle
Viral enzyme lyses the
bacterium’s cell wall, releases
new viral particles
Lysogenic
Cycle
Viral DNA forms
plasmid
Viral proteins and
nucleic acids assemble
into complete viral
particles
Go to
Section:
Viral DNA (prophage)
can exit the bacterial
chromosome
Prophage
Viral DNA (prophage)
replicates with bacterium for
many generations
Viral DNA inserts itself into
bacterial chromosome
AIDS
Acquired Immune Deficiency Syndrome
Slide # 11
1. The immune crippling disease caused by the HIV
virus in which the body becomes unable to
protect itself against any secondary infections.
2. HIV-Human Immunodeficiency Virus
3. HIV infects the immune system cell called
Helper T cells (-most important white blood cell
involved in identifying infections.)
Slide # 12
Body Fluids with High Concentrations of HIV
1. Blood
2. Semen/Vaginal
fluids (as high as
blood)
3. Breast milk
4. Pus from sores
Slide # 13
Low Concentrations of HIV
It is highly unlikely you will be infected if you
come into contact with:
a.Sweat
b.Tears
c.Urine
d.Saliva (-highly possible if blood from mouth
sores is present)
Slide # 14
How is HIV Spread?
1. ANY type of unprotected sexual activity (highest risk)
2. Sharing used drug needles
3. Pregnancy-from mother to child
4. Sharing razors- if blood is present
5. Kissing- if even the smallest amount of blood is present.
(-membranes of mouth are thin enough for HIV to enter
straight into the body.)
6. Tattoos /body piercing if equipment is not clean.
Slide # 15
How is HIV not spread
1. Shaking hands
2. Hugging
3. Swimming pools
4. Toilet seats
5. Insect bites
6. Donating blood
Slide # 16
Retrovirus
1. RNA virus that changes
its RNA into DNA when
inside the host cell.
2. Contains reverse
transcriptase enzymes.
3. Example of a Retrovirus
is HIV .
Reproduction
of HIV
Can HIV be cured?
1. NO! Drugs are available to manage the
disease, but HIV stays in the body forever!
2. PROBLEM: RNA viruses mutate at a very
high rate. A person with HIV under control
can evolve resistance to the drug treatments.
3. Some infected persons have several strains
of HIV in their bodies.
What does HIV look like?
Initial infection- flu-like symptoms a few weeks
after infection.
Stage 1:HIV positive with no symptoms- can stay
at this stage for up to 10 years, but still can pass
on the virus.
Stage 2:HIV positive with symptoms- person is
said to have AIDS. Symptoms include:
– swollen glands, chronic diarrhea, loss of
weight and appetite, fever, fatigue, skin
rashes (lesions), night sweats, oral thrush.
Life expectancy: 2 to 5 years.
Death and AIDS
Stage III-Full blown AIDSa. Person dies of rare opportunistic infections
that take advantage the weakened
immune system:
b. Person dies in a matter of months.
c. AIDS related illnesses include rare
cancers and Pneumonia.
1. HIV Virus attaches to host cell’s surface
Example
2. HIV seeks out the nucleus and injects its genetic information
3. HIV directs the cell to make new HIV virus
parts, which are then assembled.
4. New HIV viruses break out of the cell, and
spread to take over other host cells. The cell is
destroyed (lysis) as a result.