Importance of diffusion to living organisms

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ASIF AFZAL

Importance of diffusion to living organisms

Diffusion is basically the movement of chemical species (ions or molecules) under the influence of concentration difference. The species will move from the high concentration area to the low concentration area till the concentration is consistent in the whole system. Diffusion mostly occurs in gases and liquids as these can move freely.

The main features of an efficient diffusion system would be that it has a large surface area, thin membrane and a continuous supply of substances. A large surface area is needed so that high amount of substances can be exchanged at a time while the thin membrane means that the diffusion pathway would be short so that it is more efficient. The continuous supply would help in maintaining a concentration gradient which is essential for diffusion to take place.

The 2 main types of diffusion are simple and facilitated. Simple diffusion is when a small, non-polar molecule passes through a lipid bilayer. In this type of diffusion, a hydrophobic molecule moved into the hydrophobic region of the membrane without getting rejected. A key feature is that it does not need a carrier protein to take place. An example of simple diffusion is osmosis.

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Facilitated diffusion on the other hand is dependant on carrier proteins to transport it across the membrane.

Diffusion is essential for many organisms as it is a feature of a number of processes which control and supply vital substances to the body in order for basic survival. A few of these are discussed below.

Gas exchange is one of these processes. It is when much needed oxygen is obtained by the body in order for respiration to take place and the waste CO2 is taken out of the body. In us mammals, the exchange takes place in the lungs which ...

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*** This piece of writing discusses diffusion in the right way with a good range of relevant examples. However, it does not gain a higher star rating because of a lack of detail. Examiners want to see evidence that candidates have learned new content at AS and A level and that they can use A level terminology correctly and in the right context. If particular terms are used it is important that a candidate shows that they really understand what those terms mean.