Biology - B2 Keeping Healthy

• Micro-organism include bacteria, fungi and viruses. some of these cause infections diseases.
• The effect the infection(bacteria, virus or fungi) has on the body such as fever 
• Different micoorganisms cause different symptons and infecttions 
• the damage is done to te body's cells 

For example, 

Malaria parasites invade red blood cells and mutiply inside them, eventually causing them to burst open. Malaria causes flu like symptons 

Bacteria reproduces by making copies of itself, they need nutrients and warm, moist conditions so that the chemical reactions can take place. in the body there are lots of warm places.

Viruses need other cells to reproduce - they use parts of the other cells to make copies of theselves.

you can work out the size of a microoganism popuation after a certain amount of time, you need to know:

• the number of microorganisms before reproduction starts 
• how long it takes for one microorganism to reproduce 
• how long the microorganisms are left to reproduce for             same unit of time e.g. mins
• 
  

The immune system fights off any infectious microorganism that enter the body that shouldn't. The white blood cells are what take part in the immune system, and there are many different types of white blood cells that are all involved.

Some white blood cells.....

1) anything that gets into the body that shouldn't be there, anything that is foreign, should be detected by a certain type of white blood cells.
2) the white blood cells should have picked up things like microorganisms
3) which they then engulf and digest

Other white blood cells....

Antibodies recognise foreign microorganisms which makes the process much faster. This is a different group of white blood cells that fight off specific microorganisms.
They recognise particular ANTIGENS ( a toxin, foreign substance which induces the immune response in the body). So instead of engulfing them and digesting, the white blood cells produce ANTIBODIES ( proteins that are specific to a particular antigen, for example a microorganism that causes flu will have specific antigens, so the white blood cells will produce antibodies that are specific for that antigen)

The antibodies released latch onto the invading microorganisms and either
-mark microorganism so that other white blood cells can engulf it

• bind to neutralise toxins
• attach to the toxins and kill the directly

Once the right right white blood cell recognises the rights antigens it divides to make more identical cells high make more antibodies and fight the infection faster. Some white blood cells stay around after the original infection has been fought off - these are called memory cells.
Memory cells can reproduce very quickly if the same antigen enters the body for the second time, the white blood cell can produce loads of antibodies that will kill the microorganism before you become ill- immunity.