Download STRUCTURE TYPES OF INFECTIONS DNA or RNA Protein coat

VIRUS
TYPES OF
INFECTIONS
STRUCTURE
DNA
or
Protein
coat
Lytic
infection
Lysogenic
infection
RNA
Host
cell will
burst
Host
cell will
NOT
burst
WHAT IS A VIRUS?
•
Viruses are made of Nucleic Acids (DNA or RNA) and surrounded by a
protein coat.
– This protein coat is called a capsid
•
Viruses can only reproduce inside another cell called a host
•
Outside of a host cell, viruses cannot function.
– A host can be ANY type of cell
Q: What are some types of cells that viruses can infect?
A: animal cells, plant cells, bacteria cells
• Viruses that infect bacteria cells are called bacteriophages
• Q: What are the names of some viruses that you’ve heard of?
• A: influenza virus, ebola virus, smallpox virus, rhinovirus (common cold)
http://player.discoveryeducation.com/index.cfm?guidAssetId=6A96BF0C-1627-468E-845DE352B783CBEA&blnFromSearch=1&productcode=US
-What is a virus? 1:52
-How virus’ reproduce? 3:21
Viruses vary widely in their shape and complexity.
Viral Infections
•
There are 2 types of viral infections:
–
1. Lytic infections
1.LYTIC INFECTIONS:
The steps of the lytic cycle are:
1. A virus particle attaches to a host cell.
2. The particle releases its DNA into the host
cell.
3. This DNA recruits the host cell's enzymes.
4. The enzymes make parts for more new virus
particles.
5. The new particles assemble the parts into
new viruses.
6. The new particles break free from the host
cell.
2. Lysogenic infections
Once inside the host cell:
• Because one virus can reproduce
thousands of new viruses, viral
infections can spread quickly
throughout the body.
EXAMPLE:
• This is what happens when you come down with the flu or a cold:
1. An infected person sneezes near you.
2. You inhale the virus particle, and it attaches to cells lining the sinuses in your nose.
3. The virus attacks the cells lining the sinuses and rapidly reproduces new viruses.
4. The host cells break, and new viruses spread into your bloodstream and also into
your lungs. Because you have lost cells lining your sinuses, fluid can flow into your
nasal passages and give you a runny nose.
5. Viruses in the fluid that drips down your throat attack the cells lining your throat and
give you a sore throat.
6. Viruses in your bloodstream can attack muscle cells and cause you to have muscle
aches.
-Virus crisis-3:49
http://video.nationalgeographic.com/video/player/science/health-human-body-sci/health/virus-crisis-sci.html
-How flu viruses
attack- 3:47
2. Lysogenic Infections
•
•
•
•
•
•
Once inside the host cell, some viruses, such as herpes and HIV, do not reproduce
right away
Instead, they mix their genetic instructions into the host cell's DNA
When the host cell reproduces, the virus’ DNA gets copied & reproduced as well
The host cells can go through many rounds of reproduction, and then something
will trigger and ‘wake up’the "sleeping" viral DNA
Some viruses can "sleep" inside the genetic instructions of the host cells for years
before reproducing
The virus’ DNA will then take over the host's enzymes and make new viruses
Reducing the Spread
• How viruses spread:
– Carrier organisms - mosquitoes, fleas
– The air
– Direct transfer of body fluids from one person to another - saliva, sweat,
nasal mucus, blood, semen, vaginal secretions
– Surfaces on which body fluids have dried
• Things you can do to reduce the spread:
– Cover your mouth or nose when you sneeze or cough.
– Wash your hands frequently, especially after going to the bathroom or
preparing food.
– Avoid contact with the bodily fluids of others.
Comparing Viruses & Cells
Characteristic
Structure
Reproduction
Genetic Information
Obtain & Use Energy
Respond to the
Environment
Change over time
Virus
Genetic info
(DNA or RNA)
&
protein coat
Cell
Genetic info
(DNA & RNA)
& lots of
organelles
Only inside a
host cell
Independent
cell division
DNA or RNA
DNA & RNA
No
Yes
No
Yes
Yes
Yes
Vaccines
• A vaccine improves immunity to a particular disease.
• A vaccine is often made from weakened or killed forms of this microbe or its
toxins.
• This stimulates the body's immune system to recognize the agent as foreign,
destroy it, and "remember" it, so that if it enters your body again, your white
blood cells recognize and destroy it quickly
http://player.discoveryeducation.com/index.cfm?guidAssetId=163D7D9F-78CF-4905-B94AD836C7B330B6&blnFromSearch=1&productcode=US
Vaccines-2:55