Edexcel GCSE Topic 5 – Health and medicine
Diseases
A disease is a condition which causes part of an organism to function incorrectly. These
can be communicable (diseases that can be spread) or non-communicable (can’t be
spread). Some diseases make you more susceptible to other diseases.
Pathogens
Pathogens are organisms that cause disease. These mainly cause communicable
diseases.
Bacteria are small prokaryotic cells which can reproduce rapidly. They usually produce
toxins that damage cells and tissues.
Viruses are not cells. They reproduce rapidly using the machinery inside the cells they
target, which will then burst, releasing the new viruses. The damage is what makes you
feel ill.
Protists are eukaryotes, most of which are single-celled. They are usually transferred by
a vector organism, which doesn’t get ill itself but instead carries the disease.
Fungi can be single or multi-celled. The multi-celled organisms have a body which is
made of hyphae (thread-like structures). These hyphae can penetrate organisms,
causing diseases or can spread spores, which cause diseases as well.
Pathogens can be waterborne or airborne, spreading through water or air. They can also
be spread through contaminated food (known as oral transmission) or through bodily
fluids. They can also be spread through vectors (as seen with protists).
Viruses
Viruses reproduce through two pathways, lytic and lysogenic.
The lytic pathway is when the virus latches onto a host cell and injects its genetic
material into the cell. The virus then uses the machinery to replicate itself, creating new
parts of viruses. These then assemble and the cell bursts, releasing the new viruses.
The lysogenic pathway starts the same way, with the virus injecting its genetic material
into the cell. This is then incorporated into the DNA of the cell. The DNA gets replicated
when the cell does, creating many copies of the genetic material. A trigger will cause the
material to enter the lytic pathway at some point.
Defences
There are two types of defences, physical and chemical.
Diseases
A disease is a condition which causes part of an organism to function incorrectly. These
can be communicable (diseases that can be spread) or non-communicable (can’t be
spread). Some diseases make you more susceptible to other diseases.
Pathogens
Pathogens are organisms that cause disease. These mainly cause communicable
diseases.
Bacteria are small prokaryotic cells which can reproduce rapidly. They usually produce
toxins that damage cells and tissues.
Viruses are not cells. They reproduce rapidly using the machinery inside the cells they
target, which will then burst, releasing the new viruses. The damage is what makes you
feel ill.
Protists are eukaryotes, most of which are single-celled. They are usually transferred by
a vector organism, which doesn’t get ill itself but instead carries the disease.
Fungi can be single or multi-celled. The multi-celled organisms have a body which is
made of hyphae (thread-like structures). These hyphae can penetrate organisms,
causing diseases or can spread spores, which cause diseases as well.
Pathogens can be waterborne or airborne, spreading through water or air. They can also
be spread through contaminated food (known as oral transmission) or through bodily
fluids. They can also be spread through vectors (as seen with protists).
Viruses
Viruses reproduce through two pathways, lytic and lysogenic.
The lytic pathway is when the virus latches onto a host cell and injects its genetic
material into the cell. The virus then uses the machinery to replicate itself, creating new
parts of viruses. These then assemble and the cell bursts, releasing the new viruses.
The lysogenic pathway starts the same way, with the virus injecting its genetic material
into the cell. This is then incorporated into the DNA of the cell. The DNA gets replicated
when the cell does, creating many copies of the genetic material. A trigger will cause the
material to enter the lytic pathway at some point.
Defences
There are two types of defences, physical and chemical.
