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Unit 4 – The Natural Environment and Species Survival

INFECTION PREVENTION:
How can infections be prevented?
SKIN
-Skin’s keratin outer layer is effective in stopping entry of microorganisms
...

-Large numbers of skin flora live on the skin surface which prevents colonisation by other
bacteria
...

-Mucus secreted by goblet cells in the trachea and bronchi traps microbes
...

DIGESTIVE SYSTEM
-Gastric juices secreted by gastric glands in the stomach walls contain hydrochloric acid that
kills most bacteria that enter with food
...
The antigens in the
vaccines did not cause the disease but stimulated a specific immune response which
provides immunity
...

-Active natural immunity involves the body having a supply of antibodies and B memory and
T memory cells from previous exposure to the disease meaning that the body will respond
quickly if re-infected with the pathogen
...


TYPES OF VACCINES:
What are the four different components of different vaccines?
-Attenuated viruses are viruses that have been weakened so they are harmless e
...
measles
vaccine
...
g
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-A toxin that has been altered into a harmless form e
...
diphtheria vaccine
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g
...

What is herd immunity?
-This is where enough people are immunised so disease is less likely to be transferred and
less disease in the community
...

-Protease inhibitors which inhibit the proteases that catalyse the cutting of larger proteins
into small polypeptides for use in the construction of new viruses
...
The host’s
own immune system can then destroy the pathogens
...
If a weak wall forms, this can lead to lysis
(bursting) of the cell
...

-Inhibition of nucleic acid synthesis, replication and transcription
...

-Inhibition of protein synthesis meaning enzymes and other essential proteins are not
produced
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