AS Biology Unit 1 Causes of Disease AQA

Made these notes for my year 12 summer exam to revise and read over. There are spelling mistakes in most of my files but due to the busy exam schedule I had no time to correct them (sorry).

Most files have more information than what is needed but I feel it helps you feel more confident walking into the exam if you have a greater knowledge background and may help when having to apply knowledge to questions. Good luck :)

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  • Created by: Chelcie
  • Created on: 02-09-13 12:31
Preview of AS Biology Unit 1 Causes of Disease AQA

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Causes of Disease
Microorganisms as pathogens must:
Gain entry to the host,
Colonise the tissues of the host,
Resist the defences of the host,
Cause damage to the host tissues.
How do microorganisms get into the body?
By penetrating the organism's interfaces with the environment. Through:
Gas exchange system
Digestive system
Mucous layer that covers gas exchange surfaces
Production of bacteria digesting enzymes
Stomach acid
Cause of disease?
Damaging host tissues ­ viruses prevent synthesis of DNA, RNA and proteins inside body
cells. Pathogens can break down the membranes of host (body) cells.
Producing toxins ­ Bacterial pathogens can produce toxins.
Pathogens, lifestyle and genetic factors are also involved.
Correlation occurs when a change in one variable is reflected by a change in the other.
You can say something has a correlation, but not the cause (need a clear casual connection to prove a
Need to involve other lifestyle factors which graphs cannot show.
Is a measure of the probability that damage to health will occur as a result of a given hazard
Risk is the probability of the hazard occurring, and the consequences of it occurring.
Risk is often measured in %
Risk is often relative to another example e.g. smokers and non-smokers
Lifestyle choices and cancer
Physical activity


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