A* A Level Biology Essay on topic of 'Importance of Diffusion in Living Organisms'
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Unit 2 - Cells
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AQA
A* A Level Biology Essay on topic of 'Importance of Diffusion in Living Organisms'. Completed to a high standard, teacher corrections included. Four topics in great detail with evaluation and real world application. Thinks to question throughout and specialist vocab used.
The Importance of Diffusion in living organisms
Diffusion is the net movement of particles from an area of high concentration to an area of
low concentration. This is a passive process and does not require any ATP and continues
until equilibrium is reached. Diffusion is necessary to life as many vital processes in the body
rely on the diffusion of molecules, e.g. gas exchange in the lungs, or photosynthesis. There
are two main branches of diffusion; simple diffusion which is the movement of particles
across a membrane; facilitated diffusion which is the movement of particles across a
membrane using a protein, either a carrier protein or a channel protein.
Breathing is a vital process that replenishes the body’s supply of oxygen for cells to undergo
constant respiration. Without a constant supply of oxygen, cellular damage/death can occur
as processes within cells are stopped. Every element of our body relies on this oxygen
supply, from digesting our food, to our muscles in our legs when we go for a run. This gas
exchange occurs in the lungs of humans. When we inhale, the lung pressure drops causing
air to flow down the pressure gradient, through the lungs network and into the alveoli.
Oxygen then diffuses out of our alveoli into our blood stream via a network of capillaries
which is important for the transport of oxygen around the body. Oxygen binds with the
haemoglobin and travels to the muscles in our body that require the energy from
respiration (the muscles undergoing aerobic respiration). This is important as it allows our
muscles enough energy to contract for movement. Diffusion in the lungs also allows the
waste product of carbon dioxide to be released as we exhale. The alveoli are perfectly
adapted for this gas exchange, from their large surface area to the masses of capillaries
surrounding them, for the shortest diffusion pathway possible. Allowing a quick and efficient
diffusion and maintaining the diffusion gradient. Oxygen binded to the haemoglobin then
goes to cells to undergo respiration, the production of ATP. The oxygen allows the ATP to be
synthesized into ADP. The hydrolysis of ATP releases energy in the cell for other processes
that require it, e.g. active transport which requires energy to go against a concentration
gradient.
Another reason why diffusion is important in organisms is that it supplies our cells with
glucose and amino acids. Glucose is a monosaccharide we receive when eating food, vital
for energy for the completion of processes within cells. An example of this is in the ileum to
the small intestine via co-transport when we digest food. The concentration of glucose is
too low for glucose to diffuse out of the blood, so this is why glucose is absorbed in the
ileum. The sodium-potassium pump transports sodium ions out of the epithelial cells and
into the ileum against the concentration gradient via active transport using ATP. Since the
concentration of sodium is higher outside of the cell some sodium ions diffuse down their
concentration gradient via the sodium-glucose co-transport proteins. The protein carries the
sodium and the glucose molecule into the cell. When the concentration in the cell is high
some glucose molecules diffuse out of the cell and into the blood stream via facilitated
diffusion with a channel protein. Glucose diffusion is one of the most important processes in
our body as it provides energy for vital processes such as the contraction of muscles, like
skeletal muscles in exercise. It also is important in Aerobic respiration, when the cell uses
glucose primarily during exercise. When the cell lacks In glucose, anaerobic respiration is
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