Changes

[[Diffusion]] is when [[particlesparticle]] s spread from a region of high [[concentration]] to a region of low [[concentration]].

: [[Diffusion]] can only happen in a [[fluid]] which means (a [[liquid]] or a [[gas]] ) because the [[particle]]s can move past each other.

: In [[diffusion]] the particles [[particle]]s always spread from a high [[concentration]] (where there is are lots of the substance[[particle]]s, to a low [[concentration]] (where there is are less of the substance.: [[Diffusion]] stops when all [[substanceparticle]]s are spread out equally and there is no longer a [[Concentration Gradient|concentration gradient]]).

'''[[Diffusion]] is when [[substanceparticle]]s spread from a region of high [[concentration]] to a region of low [[concentration]] along a [[Concentration Gradient|concentration gradient]]. ===About Diffusion===: [[Diffusion]] can only happen in a [[fluid]] (a [[liquid]] or a [[gas]]) because the [[particle]]s can move past each other.: [[Diffusion]] cannot happen in a [[solid]] because the [[particle]]s are held in fixed positions.: In [[diffusion]] the [[particle]]s always follow the [[Concentration Gradient|concentration gradient]] spreading from a high [[concentration]] (where there is lots of the [[particle]]s), to a low [[concentration]] (where there are less of the [[particle]]s).: [[Diffusion]] stops when all [[substance]]s are spread out equally and there is no longer a [[Concentration Gradient|concentration gradient]]. {| class="wikitable"|-|[[File:Diffusion.png|center|600px]]|-| style="height:20px; width:600px; text-align:center;" |This [[diagram]] shows a high [[concentration]] of blue [[particle]]s on the left separated from the red [[particle]]s by a barrier. When the barrier is removed the blue [[particle]]s [[Diffusion|diffuse]] to the area of lower [[concentration]] on the right. [[Diffusion]] continues until all [[particle]]s are equally spread.|} {| class="wikitable"|-|[[File:Diffusion.gif|center]]|-| style="height:20px; width:600px; text-align:center;" |This animation shows a high [[concentration]] of red [[particle]]s initially at the top. When [[diffusion]] begins the red [[particle]]s spread to the area of lower [[concentration]] at the bottom. [[Diffusion]] continues until all [[particle]]s are equally spread.|} ===References=======AQA====

:[https://www.amazon.co.uk/gp/product/1782945954/ref=as_li_tl?ie=UTF8&camp=About Diffusion across a Membrane1634&creative=6738&creativeASIN=1782945954&linkCode=as2&tag=nrjc-21&linkId=100574c08fbbb64318256eb79ed61a76 ''Diffusion pages 51-53, GCSE Biology, CGP, AQA '']: [[https://www.amazon.co.uk/gp/product/0198359373/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=0198359373&linkCode=as2&tag=nrjc-21&linkId=952a73bbb09d222ecc4b50d200679849 ''Diffusion]] in [[Cell (, pages 14-15, 61, 188-189, GCSE Biology)|cells; Third Edition, Oxford University Press, AQA '']] is a passive process which means it does not require :[[energyhttps://www.amazon.co.uk/gp/product/1782945598/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782945598&linkCode=as2&tag=nrjc-21&linkId=ad276ad49df77ab4b40ab4fd0fe09843 ''Diffusion, pages 17, 20, 21, GCSE Combined Science; The Revision Guide, CGP, AQA '']] to take place.: When [[Cell (https://www.amazon.co.uk/gp/product/1782945563/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782945563&linkCode=as2&tag=nrjc-21&linkId=9a1d023a374038e6072f33c4f3cf808b ''Diffusion, pages 20, 21, 23-25, GCSE Biology)|cells; The Revision Guide, CGP, AQA '']] are surrounded by a high :[[concentrationhttps://www.amazon.co.uk/gp/product/0008158754/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=0008158754&linkCode=as2&tag=nrjc-21&linkId=27ad53b0283feeff7fc5ae04a9e205f221 ''Diffusion, pages 44-5, 55, 68-9, 86-7. 92, 94-5, 101, 106-7, 113, 117, 204, GCSE Biology; Student Book, Collins, AQA '']] of a :[[nutrienthttps://www.amazon.co.uk/gp/product/1782946381/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782946381&linkCode=as2&tag=nrjc-21&linkId=5ec5fc3f6429e30c1d9ab9bca2bccf93 ''Diffusion, pages 45-47, GCSE Combined Science Trilogy; Biology, CGP, AQA '']] then the [[nutrient]] will [:[https://www.amazon.co.uk/gp/product/1471851338/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1471851338&linkCode=as2&tag=nrjc-21&linkId=425855d5890466e47189e1c21b67a1ea ''Diffusion|diffuse]] through the [[Cell Membrane|cell membrane]] and into the [[Cell (, pages 5, 28, 29-33, GCSE Biology)|cells], Hodder, AQA ''].: When a [[Cell (Biology)|cellhttps://www.amazon.co.uk/gp/product/1471851354/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1471851354&linkCode=as2&tag=nrjc-21&linkId=9012a0d354024419214fb3ad5ac44ba0 ''Diffusion, pages 5, 29, GCSE Combined Science Trilogy 1, Hodder, AQA '']] has filled with a large number of waste :[[chemicalhttps://www.amazon.co.uk/gp/product/1471851354/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1471851354&linkCode=as2&tag=nrjc-21&linkId=9012a0d354024419214fb3ad5ac44ba0 ''Diffusion; in other organisms, pages 31-2, GCSE Combined Science Trilogy 1, Hodder, AQA '']]s they will [:[https://www.amazon.co.uk/gp/product/1471851354/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1471851354&linkCode=as2&tag=nrjc-21&linkId=9012a0d354024419214fb3ad5ac44ba0 ''Diffusion|diffuse]] through ; in the [[Cell Membrane|cell membranelungs, page 30, GCSE Combined Science Trilogy 1, Hodder, AQA '']] out of the :[[Cell (Biology)|cellhttps://www.amazon.co.uk/gp/product/1471851354/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1471851354&linkCode=as2&tag=nrjc-21&linkId=9012a0d354024419214fb3ad5ac44ba0 ''Diffusion; influencing factors, pages 32-3, GCSE Combined Science Trilogy 1, Hodder, AQA '']].

===Factors Affecting Diffusion across a Membrane=Edexcel====*[[Surface Area]] - The larger the [[Surface Area|surface area]] the more quickly [[diffusion]] can take place across the [[membrane]].*Thickness - The thinner the [[membrane]] the more quickly [[diffusion]] can take place across the [[membrane]].*[[Concentration Gradient]] - The greater the difference between the [[concentration]] on each side of the [[membrane]] the more quickly [[diffusion]] can take place across the [[membrane]].

:[https://www.amazon.co.uk/gp/product/1782948120/ref=as_li_tl?ie=UTF8&camp=Adaptations for Diffusion1634&creative=6738&creativeASIN=1782948120&linkCode=as2&tag=nrjc-21&linkId=dedef775c6a43dbb0a609441525adac0 ''Diffusion, factors affecting rate, page 258, GCSE Biology, CGP, Edexcel '']: The [[lung]]s and [[Small Intestine|small intestine]] are specially [[Adaptation|adapted]] exchange surfaces that maximise the rate of [[diffusion]]https://www.amazon.co.uk/gp/product/1782945741/ref=as_li_tl?ie=UTF8&camp=1634&creative=Lungs6738&creativeASIN=1782945741&linkCode=as2&tag=nrjc-21&linkId=30da4f2178da182547b62a7329d13b57 ''Diffusion, page 18, GCSE Combined Science; The [[lungRevision Guide, CGP, Edexcel '']]s must be able to :[[Absorb (https://www.amazon.co.uk/gp/product/1782946748/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782946748&linkCode=as2&tag=nrjc-21&linkId=a4f0348fc37d0ba1bb52d27f8679581f ''Diffusion, page 21, GCSE Biology)|absorb]; The Revision Guide, CGP, Edexcel ''] :[[Oxygenhttps://www.amazon.co.uk/gp/product/1292120193/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1292120193&linkCode=as2&tag=nrjc-21&linkId=572df39392fb4200db8391d98ae6314e ''Diffusion, pages 20, 92-93, 112, GCSE Combined Science, Pearson Edexcel '']] into the :[[bloodhttps://www.amazon.co.uk/gp/product/1292120207/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1292120207&linkCode=as2&tag=nrjc-21&linkId=22455ff53961978667722edaa64c0be5 ''Diffusion, pages 24, 130-131, 162, GCSE Biology, Pearson, Edexcel '']] and release :[[Carbon Dioxide]] from the [[bloodhttps://www.amazon.co.uk/gp/product/1782948120/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782948120&linkCode=as2&tag=nrjc-21&linkId=dedef775c6a43dbb0a609441525adac0 ''Diffusion, pages 48, 49, GCSE Biology, CGP, Edexcel '']] back into the [[lung]]s.: The [[lung]]s are [[Adaptation|adapted]] with thousands of [[alveoli]] which increase the surface area of the [[lung]]shttps://www.amazon.co.: uk/gp/product/1782946748/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782946748&linkCode=as2&tag=nrjc-21&linkId=a4f0348fc37d0ba1bb52d27f8679581f ''Diffusion; factors affecting rate, page 88, GCSE Biology; The walls of the [[alveoli]Revision Guide, CGP, Edexcel ''] separating the [[air]] from the [[blood]] are very thin.: The [[bloodhttps://www.amazon.co.uk/gp/product/1292120207/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1292120207&linkCode=as2&tag=nrjc-21&linkId=22455ff53961978667722edaa64c0be5 ''Diffusion; factors affecting, pages 164-165, GCSE Biology, Pearson, Edexcel '']] supply to the [[lung]]s is very good to constantly supply [[blood]] with little [[Oxygen]] and a lot of [[Carbon Dioxide]] keeping a high [[Concentration Gradient|concentration gradient]].

====Small IntestineOCR====: The [[Small Intestine]https://www.amazon.co.uk/gp/product/0198359829/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=0198359829&linkCode=as2&tag=nrjc-21&linkId=90e8d7b4f039d53035238fa0320fe00b ''Diffusion, page 123, Gateway GCSE Chemistry, Oxford, OCR ''] is long and folded to increase the [[Surface Area|surface area]].: The [[Small Intestine]] has structures called [[Villi]] which are extra folds in the surface to increase the [[Surface Area|surface area]]https://www.amazon.co.: uk/gp/product/1782945695/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782945695&linkCode=as2&tag=nrjc-21&linkId=ceafcc80bcad6b6754ee97a0c7ceea53 ''Diffusion, page 25, Gateway GCSE Combined Science; The [[Cell (Biology)|cells]] on the [[villi]] have [[microvilli]] which are folds on the [[Cell Membrane|cell membrane]] to increase the [[Surface Area|surface area]Revision Guide, CGP, OCR ''].: [https: //www.amazon.co.uk/gp/product/1782945660/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782945660&linkCode=as2&tag=nrjc-21&linkId=83aa4500ad7759e7f401a1c5ba5df758 ''Diffusion, pages 30, 33, Gateway GCSE Biology; The walls of the [[villi]] separating the food from the [[bloodRevision Guide, CGP, OCR '']] are very thin.: The [[blood]] supply to the [[villi]https://www.amazon.co.uk/gp/product/0198359810/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=0198359810&linkCode=as2&tag=nrjc-21&linkId=d768d99f1a06f7c12fab40e5aef85a55 ''Diffusion, pages 58-59, 72-73, Gateway GCSE Biology, Oxford, OCR '']s is very good to constantly supply [[blood]] with little [[nutrients]] keeping a high [[Concentration Gradient|concentration gradient]] between the food and the [[blood]].