AQA ALEVEL BIOLOGY ESSAY: THE IMPORTANCE OF RECEPTORS IN ORGANISMS
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Course
AQA biology essays (7402)
Institution
Uppingham School
Top mark AQA A Level biology essay on the importance of receptors in organisms.
includes osmoreceptors, immunity, action potentials, and transcription factors
Osmoreceptors are important receptors in the control of blood water potential
in humans. They are found in the hypothalamus in the brain. They shrink or
shrivel in response to the water potential as water will move in or out of the
osmoreceptors down a water potential gradient via osmosis. If blood water
potential is too low, water will leave by osmosis. Nerve impulses are sent
along sensory neurons to the posterior pituitary gland. These nerve impulses
stimulate the release of Antidiuretic hormone (ADH). ADH attaches to specific
receptors on the kidneys which are the target cells. That results in more
aquaporins being embedded into the walls of the collecting duct and DCT so
more water is reabsorbed from the nephron back into the blood. This brings
blood water potential back to a normal level. The receptors are important in
this process because without them, blood water potential would not be able to
be controlled so if there was too little water, substances wouldn’t be able to
travel around the body as easily as water is an important solvent, water
wouldn’t be readily available for chemical reaction such as hydrolysis. And
there would be less water for sweating which provides a cooling effect. If there
is too much water in the blood, the volume of blood increases which increases
blood pressure. Increased blood pressure can lead to damage to the
endothelium of blood vessels. Without osmoreceptors, the body wouldn’t be
able to detect changes in water levels and make appropriate adjustments.
Without the receptors on Kidney cells, ADH would not be recognised so there
wouldn’t be a response of an increasing number of aquaporins.
Receptors are a vital aspect in mechanisms of immunity and the immune
system as without them, an immune response would not be able to occur.
Receptors on foreign or dysfunctional cells have specific proteins on their
surface known as antigens which trigger an immune response by
lymphocytes. After a pathogen has been processed by phagocytosis, the
phagocyte presents the antigens on its cell surface membrane, which
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