Download Viruses

What is a Virus?
• Viruses are tiny, non-cellular,
infectious agents that invade living
cells and take over their machinery
to make copies of themselves.
based
on the characteristics of life, because they:
*Do
not make/use energy or have
any metabolism (they have no
organelles)
• Cannot reproduce on their own
• Are not made of cells
• Do not grow/develop on their
own
• Are viruses living?
no
• Why? Be specific?
Does not have all the
characteristics of life, cannot
survive or reproduce without alone
without a host, no metabolism, not
made of cells
Virus Structure
Bacteriophage
Infects bacterial cells
1.Capsid – made of
protein,
contains the genetic
material
(DNA or RNA)
2. Tail
3.Tail Fibres- used for
attaching to target cell
HIV
Influenza
Human Immunodeficiency
Virus
‘The Flu’
1.Capsid –
made of protein,
contains the
genetic material
(RNA)
Antigens - made of lipids/glycoproteins, help the
virus to attack and enter their target
Also help the immune system to identify
the virus
Flu Attack! How a Virus Invades Your Body
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Viruses Vocab
• Viruses are obligate parasites –
organisms that need to invade a
living cell or being to survive and do
not benefit them in any way
• Host - The organism/cell that a
parasite exploits
• Viruses are pathogens – something
that causes disease in the host
cell/organism
• What is a parasite?
• What is a host?
• What is a pathogen?
How Viruses Work
Step One – Viruses attach to their specific target
cell based on their antigens. This works like a
lock and key, so viruses will only affect certain
cells.
• Step Two – virus injects its
genetic information into the host
• Step Three – Replication (copies)The
cell now starts to make copies of the
virus proteins and genetic information
• Step Four –Assembles-the different
parts of the virus are assembled into full
virus copies
• Step Five – LYSIS (cell bursting apart)
and the virus copies are released to
infect other cells
• What are the 5 steps of the Lytic
Cycle?
• 1. attack
• 2. inject
• 3. replicate
• 4. assemble
• 5. Lysis
How Viruses Work
Lytic/Lysogenic Cycles
Viruses can infect cells in two different ways
1. Lytic Cycle (short cycle)If a virus
enters and immediately causes
infection with the 5 steps Ex. flu
Lytic/Lysogenic Cycles
Viruses can infect cells in two different ways
2. Lysogenic Cycle (long cycle) If a
virus enters and remains
dormant/inactive in the DNA
before causing infection ex. HIV,
Herpes
I’m a Virus! Rap Song
Immune Response-Your immune
system recognizes viruses and bacteria
based on their surface antigens
Every cell in your body has your specific markers, so anything that
looks different is marked by your body as an invader
(this is why people need specific organ transplants and also why you
can’t receive blood transfusions from everyone)
Immune Response
The Immune System protects the body in two ways:
1. Nonspecific Response: Skin, mucus,
sweat, tears, saliva, stomach acid,and
inflammatory response (heat, redness,
swelling, and white blood cells)
2.Specific Response: Body makes
antibodies which seek out and kill
specific antigens
Immune System, part 1: Crash Course A&P #45
Immune Response
The immune
system is
incredibly
complex which is
why it has an
entire branch of
science called
immunology
Brace yourself for the next slide!!
Specific Response
There are many cells that are responsible for the specific immune response:
Macrophages/Phagocytes- Large cells that ‘eat’ the virus/bacteria and show the T Cells and B
Cells the antigen to target
Helper T Cells – Cells that tell B Cells, Cytotoxic T Cells,
and Natural Killer Cells what to do
B Cells – Cells that make Plasma Cells and Memory B Cells
Plasma Cells – Cells that make antibodies which target the virus/bacteria
Memory B Cells- Cells that ‘remember’ the antigen so they can quickly kill the virus/bacteria if it
shows up again later
Cytotoxic T Cells – Cells that make poison granules to kill the virus/pathogen
Natural Killer Cells - Cells that kill any infected or out of control (cancer) cells
Specific Response
HIV attacks Helper T
Cells which greatly
weakens the
immune system
This is how HIV (the
virus) causes AIDS Acquired
Immunodeficiency
Syndrome (the disease)
Medication
Anti tics are medications that kill
living cells so they are used against
living pathogens like bacteria, (useless
against viruses)
• Viruses are very
difficult to target
with medications
because they are
not living by our
definition of life
• Antibiotics treat strep throat, ear
and sinus infections, pneumonia,
any type of bacteria infection.
Vaccines help fight viruses.
• A vaccine actually
contains
weakened (dead,
wrong use of the
word) viruses
that trigger the
immune system
to start making
antibodies which
will protect you
in the future
Some Vaccines
that are available
Keep in mind that not all
vaccines are 100% effective
Currently available vaccines:
*Hepatitis A, B
• HPV
• Influenza (The Flu)
• Measles, Mumps,
Rubella, Varicella
• Meningococcal
• Shingles
• Varicella (Chickenpox)
• Adenovirus
• Anthrax
• Japanese Encephalitis
• Rabies
• Smallpox
• Typhoid
• Yellow Fever
Which of the following are
viruses?