the essay writes about 5 important processes in the body where receptors play an important role in survival. The essay uses key terminology following aqa a level biology specification closely.
Write an essay on the importance of receptors in living organisms.
Receptors play a vital role in the immune response. When foreign antigens are detected by the
phagocytes they form a phagosome around it and fuse with lysosomes which release,
lysozymes which hydrolyses the antigens and present them on the surface of the cell
membrane. The receptors on the helper T cells are complementary to the antigens and bind
together to stimulate B cells to clone by mitosis to produce plasma cells which secrete
antibodies and memory B cells. Without the presence of the receptors on the helper T cells,
there would be no [production of antibodies so cell agglutination can`t occur so its more difficult
for the antigens to be hydrolysed by phagocytes.Moreover no memory B cells or T cells
produced which means that the body will continuously undergo primary response which means
that there will be reocurring sickness to the same pathogen and we will have no immunity
against a particular pathogen. The receptors on the T-cells allow the production of antibodies
which has led to the development in the production of vaccines as the vaccines can have a
dead version of the pathogens which can allow the body to have a primary response to produce
antibodies against the antigen and without the receptors there would no production of these
antibodies it is vital for human survival.
Another importance of receptors is shown by osmoreceptors which are used to maintain the
body water level. When the water potential in the blood is low water moves out of the
osmoreceptors by osmosis and causes the osmoreceptors to shrink this then stimulates the
pituitary gland to release ADH which increases the permeability of the DCT and the collecting
duct to water. in the loop of Henle of the kidney, sodium ions are actively transported out of the
ascending, limb to the medulla lowering the water potential in the medulla so water moves out
by osmosis from the descending limb down the water potential gradient. This maintains a
concentration gradient allowing the counter-current flow so water can then be reabsorbed from
the collecting duct and duct by osmosis because the ADH increases its permeability. This is an
example of negative feedback and the opposite process occurs if the water potential is too high.
osmoreceptors play a crucial role as it maintains the water level in the body go allow metabolic
reaction such as hydrolysis and condensation reactions to occur. Moreover, water is also
important because it has a high latent heat of vaporisation so sweating has a cooling effect so it
allows the maintenance of body temperature, lately water has a high specific heat capacity so it
acts an as a buffer allowing the enzymes in the body to work at optimum conditions. All these
properties of water are effective in the body due to the maintainance of its level which is
because of the presence of the osmoreceptors.
Another importance of receptors is in the travelling of impulses from one neurone to another
particular the cholinergic synapse. When the action potential arrives at the synaptic neurone
and stimulates the calcium ions channels to open in the presynaptic neurone so calcium ions
diffuse in and stimulate the vesicles containing neurotransmitters such as acetylcholine to fuse
with the presynaptic membrane and release the neurotransmitter to the synaptic cleft. The
neurotransmitters are then diffused across the synaptic cleft and bind to the receptors on the
postsynaptic neurone and cause the sodium channel to open allowing the influx of sodium ions
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