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Core Biology Smart Teach 5: Disease
and Immune System
Key terms used in exam
questions
• Pathogen – An microorganism that
causes an infectious disease.
• Antibiotic – A chemical that kills
bacteria.
• Antiseptic – A chemical that is used
externally to prevent the spread of
pathogens.
• Resistant – Used in this context it
usually refers to when bacteria are no
longer killed by an antibiotic.
What are the four pathogen types you
are most likely to be asked about?
•
•
•
•
Bacteria – Causes cholera/dysentery.
Viruses – Causes influenza(‘flu)/common cold.
Fungi – Causes Athlete’s Foot
Protozoa – Causes malaria
• You also need to be able to give examples of how
they are spread through populations. The next
few slides will give the key information for each
method and an example for each.
• Airborne – Spread through the air eg colds, influenza,
Tuberculosis.
• Waterborne – Drinking infected water eg cholera.
• Food – Eating infected food eg Salmonella (Food
poisoning)
• Skin-to-skin contact – Touching an infected person, or
walking where they have eg athlete’s foot and verucas
are spread quite commonly in swimming pools.
• Body fluids – Either through infected blood or having
unprotected sex eg HIV.
• Vectors – Carriers of pathogens eg mosquitoes carry
the protozoa that causes malaria, houseflies carry the
bacteria that causes dysentery. It is the mosquitoes
and the houseflies that are the vectors.
What defences does our body have?
Mucus
Lysozymes in tears
and saliva
Cilia
Skin
Hydrochloric acid in
the stomach
Chemical vs Physical
The chemical
defences
are:
Hydrochloric
acid in the
stomach.
Lysozymes in
the tears
and saliva.
You could
be asked
to give an
example
of either
chemical
or physical
defences.
The physical
defences
are:
Skin.
Cilia.
Mucus.
Antibiotics vs. Antiseptics
Antibiotics –
You
could
be
These are
given
data
chemicals to
in
the
form
kill bacteria
of
a
graph
only.
or table to
evaluate
the use of
these
Antiseptics –
These are
chemicals to
kill pathogens
outside of the
body eg
handwash,
wipes etc.
Antibiotic resistance
• Over use of antibiotics can lead to them becoming
resistant to antibiotics eg the antibiotics will no longer
work.
• Resistance is usually due to a genetic mutation.
• MRSA has caused problems in hospitals because some
strains have become resistant to antibiotics.
• You should always finish a course of antibiotics even if
you feel better so that all the bacteria are killed and
don’t have a chance to become resistant.
• Doctors will no longer prescribe antibiotics all the time
now, they are more selective.
MRSA questions usually involve graphs
• The next slide will take you through a typical
exam question.
As time increases
Number of case of MRSA
increases
There is a steep
increase from
2000.
This increase is due to antibiotic resistant strains
of MRSA appearing in hospitals possibly due to
an increase in poor hygiene.
Now lets have a look at
some exam questions
about this..........
Answer
Question
Number
(b)
Acceptable
answers
Mark
B
(1)