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Edexcel GCSE Topic 5 – Health and medicine
Diseases
A disease is a condition which causes part of an organism to function incorrectly
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Some diseases make you more susceptible to other diseases
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These mainly cause communicable
diseases
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They usually produce
toxins that damage cells and tissues
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They reproduce rapidly using the machinery inside the cells they
target, which will then burst, releasing the new viruses
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Protists are eukaryotes, most of which are single-celled
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Fungi can be single or multi-celled
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These hyphae can penetrate organisms,
causing diseases or can spread spores, which cause diseases as well
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They can also
be spread through contaminated food (known as oral transmission) or through bodily
fluids
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Viruses
Viruses reproduce through two pathways, lytic and lysogenic
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The virus then uses the machinery to replicate itself, creating new
parts of viruses
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The lysogenic pathway starts the same way, with the virus injecting its genetic material
into the cell
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The DNA gets replicated
when the cell does, creating many copies of the genetic material
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Defences
There are two types of defences, physical and chemical
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Examples of chemical barriers include stomach acid and lysozymes (which cleave
bacterial cell walls)

The immune system
The immune system uses two types of white blood cell: phagocytes and lymphocytes
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This
is a non-specific response (they can consume any pathogen)
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They contain a receptor on the outside which is complimentary to a protein spikes
(known as antigens) present on all pathogens
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When the B-lymphocyte detects the antigen, it produces antibodies, which bind onto
the antigens of the pathogen, inhibiting reproduction
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Memory lymphocytes
Memory lymphocytes are used to speed up the response when a disease returns
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These
remain in the body much longer than B-lymphocytes
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Immunisation
Immunisation is the process of injecting a deactivated version of a pathogen or the
antigen present on it to trigger an immune response
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Monoclonal Antibodies (Higher tier only)
Monoclonal antibodies are produced from lots of clones of a B-lymphocyte
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They are
created from the B-lymphocyte specific to the pathogen and a myeloma (tumour) cell
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These can be used for pregnancy tests, using the antibodies with blue beads
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When HCG is
present, the antibodies bind to them
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If the HCG is present, the antibodies will bind to the

anti-antibodies, allowing the blue bead to show up
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Drug development
1)
2)
3)
4)
5)

A drug that works is found
This is tested firstly on tissue cultures
Then tested animals (usually apes due to the genetic similarity)
Before being tested on humans
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The placebo is a harmless pill
with similar properties to the actual drug (including nutrition and method of
administration)
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These placebo tests can be blind
(where the patient doesn’t know) or double-blind (Where neither the patient nor the
doctor knows)
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Antibiotics
Antibiotics target di erent bacteria, but not viruses
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This also means that they do not a ect human or animal cells (as we don’t have cell
walls)

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