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DISTINCTION GIVEN FOR UNIT 12A
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Unit 12AInfectious Diseases
These are diseases can enter your body from the outside and cause harm such as bacteria and
viruses
Bacteria
Bacteria are classified as prokaryotic organisms, they don't
have a nucleus or any membrane-bound organelles. They
measure between 1 to 8 micrometres in length (1)
Bacteria can be found in various different shapes and sizes.
And can also reproduce rapidly by a process called binary
fission which is when the genetic material and the plasmids get
copied inside the cell then moves to each side before the cell
divides. When a bacteria replicates rapidly it can form a colony
which can be observed to identify which bacteria it is. These
are some of the types of colonies,
Image, (2)
Bacteria damages the body by entering into a host and producing toxins to further destroy
healthy cells. Some examples include salmonella which is caused by eating contaminated foods
such as raw chicken, gonorrhoea which is a sexually transmitted disease that is spread through
sexual contact (3)
In the lag phase the bacteria adapt to their new
environment, preparing for growth but not yet dividing.
During the growth phase, bacteria multiply rapidly,
increasing in number rapidly. In the maturation phase,
growth slows as nutrients become limited. Finally, in the
death phase, bacterial numbers drop due to lack of
resources and other factors leading to cell death.(6)
, Viral Infections
A virus is classed as an akaryotic organism as it is non living.
They are missing the cytoplasm, organelles and a cell surface
membrane to be classified as a cell. They are also smaller
than bacteria at around 21-300 nm
(4)
Since viruses lack organelles, they are unable to replicate on
their own. Instead, they rely on host cells for replication, using
the host cell's organelles and metabolism. To replicate, the
viruses insert their genetic material into the host cell, causing
capsomere proteins to be made. These proteins then form new
virions. Eventually, the build of virions leads to the bursting of
the host cell, resulting in damage to the host.
(5)
Case study
Covid 19 (SARS-CoV-2)
COVID-19 primarily affects the respiratory system. The virus
enters the body through the respiratory tract, usually by
inhaling droplets containing viral particles. Once inside the
body, the virus attaches to cells in the respiratory tract,
particularly in the lungs, using spike proteins on its surface to
bind to receptors on host cells.
The virus then enters the host cells, invading their organelles
to replicate itself. This replication process damages the host
cells and triggers an immune response, leading to
inflammation in the respiratory tract. In severe cases, this
inflammation can cause pneumonia and other complications, making it difficult for oxygen to
reach the bloodstream and leading to respiratory failure. Additionally, the virus can also cause
widespread inflammation throughout the body, leading to damage in various organs and tissues.
covid-19 can also affect other systems in the body, including the cardiovascular system and
nervous system, leading to symptoms such as fever, cough, shortness of breath, fatigue, loss of
taste or smell and muscle aches. (7)(8)
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