GCSE Biology B2 (Higher)

Microgorganisms Cause Many Diseases:

Lots of microorganisms causes diseases. They are called pathogens.

Pathogen: A bacterium, virus, or other microorganism that can cause disease.

Pathogens include some bacteria, protozoa (single-celled creatures), fungi and viruses.

All pathogens are parasites - they live off their host and give nothing in return

Most microrganisms reproduce fastest in warm, damp places. This means that they tend to reproduce very quickly inside host organisms.

Once pathogens get inside their host and start reproducing, they cause an infection.

Some kinds of pathogen take longer to cause an infection than others.

Your body thankfull has many different barriers to keep microorganisms out. Some of these are:

SKIN - It's a really effective barrier for keeping microorganisms out. If the skin is damaged, it can rapidly repair itself to sop wounds getting infected.

SWEAT - Sweat contains substances that reduce the growth of the microorgansims. It forms an extra protective layer over the skin.

TEARS - Tears contain enzymes that can kill bacteria.

HYDROCHLORIC ACID IN YOUR STOMACH - Bacteria that enter your body via food or drink are usually killed off by this which stops them spreading through your body.

The role of the immune system is to deal with any pathogens that enter the body. An immune response always involves white blood cells. There are several different types and they all have different jobs to do.

1) Anything that gets into the body should be picked up straight away by a certain type of white blood cell.

2) These white blood cells are able to detect things that are 'foreign' to the body.

3) They engulf the microbes and digest them.

4) These white blood cells are non-specific - they attack anything that's not supposed to be there.

6) White blood cells also trigger an inflammatory response. Blood flow to the infected area is increased and fluid leaks into the damaged tissue. This is so that all of the right cells can get to the area to fight the infection.

After this happens, the infected area turns red and hot and starts to swell up.

Antibiotics can kill bacteria and fungi but not viruses

Things like flus and colds are caused by viruses. Antibiotics will not cure these. You just have to wait for your body to deal with them.

Bacteria can evolve and become antibiotic-resistant

Microorganisms sometimes develop random mutations in their DNA. They can lead to changes in the microorganisms characteristics.

This means that they could become more resistant to antibiotics.

Overtime, these microorganisms can devlop into 'superbugs'

So far, new drugs have kept us one step ahead but some people think that it's only a matter of time before our options run out.