B1 Fighting Disease

What you need to know for B1 Fighting disease

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  • Created on: 22-12-12 23:23
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Fighting Disease
A disease causing micro-organism is called a pathogen. We will be talking about these a lot in this
document. The main two types of pathogen you need to know about are bacteria and viruses.
Below, I have stated the main differences, the ones you need to know about for the exam.
You won't have to be able to label them (as shown in the images), unless you are doing B2.
Bacteria
These are cells
They can reproduce rapidly inside your body
They cause you to become ill by doing two main things: damaging your cells and producing toxins
Viruses
These aren't cells, they are MUCH smaller
They get inside cells in your body and start replicating themselves rapidly. As you may guess, this
would soon cause the cell to burst, releasing all the viruses around the body.
The cell damage is what makes you feel ill.
The body does various things to prevent these pathogens from entering in the first place.
1. In your respiratory tract, there is mucus and cilia (hairs), this reduces the chance of
pathogens entering from the air.
2. Then there's possibly the most obvious one, your skin. It's basically like a shield, preventing
pathogens from entering
3. However, you may be thinking, well skin isn't always there, what if you get cut? There's a
solution to that too. Our body has dead cells called platelets in the blood which clot together
to cover the skin where you have a cut. This reduces the risk of infection entering when you
have a cut. (You don't need to know much about platelets except this, unless you are doing
B3)
4. If a pathogen does make it through all of these defences, then our immune system kicks in
One of the main cells in the immune system is the white blood cell. They can do three things to stop
the pathogen.
1. They can produce antitoxins. These antitoxins counteract with the toxins produced by the
invading bacteria.
2. They can engulf and digest the foreign cells. They do this by using enzymes.
3. Probably the most confusing one, they produce antibodies.
Now, you need to know that even invading cell has a unique molecule on its surface which is
called the antigen. When the white blood cells come across these invading cells, they

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These antibodies will be specific to that one type of invading cell. The antibodies will lock onto
the invading cell and basically kill it. Then, the white blood cells will rapidly produce thousands
of antibodies to be carried around the body to kill any more similar bacteria or viruses.
Remember that bacteria and viruses replicate very quickly, so there will be more bacteria/virus
cells around the body.…read more

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