Download Viruses

Quick Activity
• Put your name on a small piece of paper
• Put the paper into the bin at the front of the
room.
• Stand by your seats and push in the chair.
• Wait for further instructions
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.
What is a Virus?
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
Virus Structure
Bacteriophage
Infects bacterial cells
MOST IMPORTANT PART
Capsid – made of protein,
contains the genetic material
(DNA or RNA)
Tail
Tail Fibres- used for
attaching to target cell
Virus Structure
Influenza
HIV
Human Immunodeficiency
Virus
‘The Flu’
MOST
IMPORTANT
PART
Capsid –
made of
protein,
contains the
genetic
material
(RNA)
Antigens - made of lipids/glycoproteins, help the virus to attach and attack their target
Also help the immune system to identify the virus
Flu Attack! How a Virus Invades Your Body
Viruses Vocab
• Viruses are obligate parasites – organisms
that need to live in/on another 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
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.
How Viruses Work
• Step Two – The virus will inject its genetic
information into the host
How Viruses Work
• Step Three – The
cell now starts to
make copies of the
virus proteins and
genetic information
• Step Four – The
different parts of
the virus are
assembled into full
virus copies
How Viruses Work
• Step Five – The virus causes cell lysis (cell
bursting apart) and the virus copies are
released
How Viruses Work
Lytic/Lysogenic Cycles
Viruses can infect cells in two different ways
1. If a virus enters and immediately causes
infection with the 5 steps, it is called the Lytic
Cycle
Lytic/Lysogenic Cycles
Viruses can infect cells in two different ways
2. If a virus enters and remains dormant/inactive in the
DNA before causing infection, it is called the
Lysogenic Cycle
Evil Mad Scientist
• You are an evil mad scientist.
• You are bent on destroying the world through
you virus.
• Would you prefer a lytic or lysogenic virus and
why?
• Turn to your partner and discuss
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:
• Nonspecific Response: Skin, mucus, sweat,
tears, and inflammatory response (heat,
redness, swelling, and white blood cells)
• Specific Response: Body makes antibodies
which seek out and kill specific antigens
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
• Viruses are very
difficult to target
with medications
because they are
not living by our
definition of life
• Anti tics are medications that are designed
to kill living cells so they are useless against
viruses
Vaccines
• Vaccines have been
developed for a number
of viruses/bacterial
infections.
• A vaccine actually
contains weakened or
dead viruses that trigger
the immune system to
start making antibodies
which will protect you in
the future
Keep in mind that not all
vaccines are 100% effective
Vaccines
Currently available vaccines:
• DTaP
• Hepatitis A, B
• HiB
• HPV
• Influenza (The Flu)
• Measles, Mumps, Rubella, Varicella
• Meningococcal
• MenB
• Pneumococcal Conjugate
Pneumococcal Polysaccharide
• Polio
• Rontavirus
• Shingles
• Tdap
• Td
• Varicella (Chickenpox)
• Adenovirus
• Anthrax
• Japanese Encephalitis
• Rabies
• Smallpox
• Typhoid
• Yellow Fever