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Exchange Surface

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Created page with "==Key Stage 3== ===Meaning=== '''Exchange surfaces''' are membranes that allow diffusion of substances across the membrane from a region of high concentratio..."
==Key Stage 3==
===Meaning===
'''Exchange surfaces''' are [[membrane]]s that allow [[diffusion]] of [[substance]]s across the [[membrane]] from a region of high [[concentration]] to a region of low [[concentration]].

===About Exchange Surfaces===
: There are several exchange surfaces you should know:
:*[[Cell Membrane]]s
:*The walls of [[alveoli]]
:*The walls of the [[intestine]]s.

===About The Cell Membrane as an Exchange Surface===
: When [[Cell (Biology)|cells]] are surrounded by a high [[concentration]] of a [[nutrient]] then the [[nutrient]] will [[Diffusion|diffuse]] through the [[Cell Membrane|cell membrane]] and into the [[Cell (Biology)|cells]].
: When a [[Cell (Biology)|cell]] has filled with a large number of waste [[chemical]]s they will [[Diffusion|diffuse]] through the [[Cell Membrane|cell membrane]] out of the [[Cell (Biology)|cell]].

{| class="wikitable"
|-
|[[File:CellDiffusion1.png|center|300px]]
|[[File:CellDiffusion2.png|center|300px]]
|-
| style="height:20px; width:200px; text-align:center;" |There is a high [[concentration]] of [[nutrient]]s outside the [[Cell (Biology)|cell]] so they diffuse through the [[Cell Membrane|membrane]] into the [[Cell (Biology)|cell]].
| style="height:20px; width:200px; text-align:center;" |The [[concentration]] of [[nutrient]]s inside the [[Cell (Biology)|cell]] and outside the [[Cell (Biology)|cell]] becomes the same.
|-
|[[File:CellDiffusion3.png|center|300px]]
|[[File:CellDiffusion4.png|center|300px]]
|-
| style="height:20px; width:200px; text-align:center;" |There is a high [[concentration]] of waste [[chemical]]s inside the [[Cell (Biology)|cell]] so they diffuse out through the [[Cell Membrane|cell membrane]].
| style="height:20px; width:200px; text-align:center;" |The [[concentration]] of waste [[chemical]]s inside the [[Cell (Biology)|cell]] and outside the [[Cell (Biology)|cell]] becomes the same.
|}

===About The Walls of the Alveoli as an Exchange Surface===
: When [[air]] is [[inhale]]d into the [[lung]]s [[Oxygen]] [[diffuse]]s from the [[air]] across the walls of the [[alveoli]] and into the [[Red Blood Cell|red blood cells]].
: Before [[air]] is [[exhale]]d out of the [[lung]]s [[Carbon Dioxide]] [[diffuse]]s out of the [[blood]] through the walls of the [[alveoli]] and into [[air]] in the [[lung]]s.
: The walls of the [[alveoli]] have several [[adaptation]]s to maximise the rate of [[diffusion]] across them:
:*The [[alveoli]] have thin walls to allow gas exchange to happen quickly.
:*[[Alveoli]] are in groups to make a large [[Surface Area|surface area]] in the [[lung]] for gas exchange.
:*The [[alveoli]] have a good [[blood]] supply to allow gas exchange with the [[blood]].
:*The walls of the [[alveoli]] are kept moist to allow [[gase]]s to [[dissolve]] into to the fluid for gas exchange with the [[blood]].

===About The Wall of the Small Intestines as an Exchange Surface===
: When food is consumed and [[digest]]ed the [[nutrient]]s can [[diffuse]] across the walls of the [[Small Intestine|small intestine]] into the [[blood]] stream.
: The wall of the [[Small Intestine|small intestine]] is [[adaptation|adapted]] to allow the movement of [[nutrient]]s from the food into the [[blood]] stream in the following ways:
:*The [[Small Intestine|small intestine]] is long to give it a large [[Surface Area|surface area]].
:*The wall of the [[Small Intestine|small intestine]] is thin to provide a short distance for [[nutrient]]s to travel from food to the [[blood]] stream.
:*The wall of the [[Small Intestine|small intestine]] is covered in [[villi]] which are small folds, also increasing the [[Surface Area|surface area]].
:**The [[Villi]] have a wall only one cell thick so the [[nutrient]]s only have a short distance to [[Diffusion|diffuse]] into the [[blood]].
**[[Villi]] have [[Capillary|capillaries]] inside them for a good blood supply to allow for quick [[diffusion]] into the [[blood]].
:**[[Villi]] have a large [[Surface Area|surface area]] to allow quicker [[diffusion]].
:**The [[Cell (Biology)|cells]] in the walls of the [[villi]] have [[microvilli]] to provide an even bigger [[Surface Area|surface area]] for quicker [[diffusion]].


==Key Stage 4==
===Meaning===
'''Exchange surfaces''' are [[membrane]]s that allow movement of [[substance]]s by [[diffusion]], [[osmosis]] or [[Active Transport|active transport]].

===About Exchange Surfaces===
: [[Membrane]]s can be [[Partially Permeable Membrane|partially permeable]] so they only allow certain [[chemical]]s to '''diffuse''' through them.
: [[Diffusion]] in [[Cell (Biology)|cells]] is a passive process which means it does not require [[energy]] to take place.
: When [[Cell (Biology)|cells]] are surrounded by a high [[concentration]] of a [[nutrient]] then the [[nutrient]] will [[Diffusion|diffuse]] through the [[Cell Membrane|cell membrane]] and into the [[Cell (Biology)|cells]].
: When a [[Cell (Biology)|cell]] has filled with a large number of waste [[chemical]]s they will [[Diffusion|diffuse]] through the [[Cell Membrane|cell membrane]] out of the [[Cell (Biology)|cell]].
: [[Osmosis]] is when a [[Cell Membrane|cell membrane]] allows [[water]] to [[diffuse]] across the [[Cell Membrane|cell membrane]] but not other [[molecules]], particularly [[sugar]]s.
: [[Active Transport]] takes place when an essential [[nutrient]] is needed in large quantities so [[Cell (Biology)|cells]] use [[energy]] to pump these [[nutrient]]s across the [[Cell Membrane|cell membrane]] against the [[Concentration Gradient|concentration gradient]].

===Factors Affecting Diffusion, Osmosis and Active Transport across an Exchange Surface===
*[[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]].
*[[Mitochondia]] - In cases of [[Active Transport|active transport]] [[Cell Biology|cells]] will have extra [[mitochondria]] to provide [[energy]] for this process.

===About The Cell Membrane as an Exchange Surface===
: When [[Cell (Biology)|cells]] are surrounded by a high [[concentration]] of a [[nutrient]] then the [[nutrient]] will [[Diffusion|diffuse]] through the [[Cell Membrane|cell membrane]] and into the [[Cell (Biology)|cells]].
: When a [[Cell (Biology)|cell]] has filled with a high [[concentration]] of waste [[chemical]]s they will [[Diffusion|diffuse]] through the [[Cell Membrane|cell membrane]] out of the [[Cell (Biology)|cell]].
: When [[Cell (Biology)|cells]] are surrounded by a low [[concentration]] of a [[nutrient]] then the [[nutrient]] will by moved by [[Active Transport|active transport]] through the [[Cell Membrane|cell membrane]] and into the [[Cell (Biology)|cells]].
: When a [[Cell (Biology)|cell]] has filled with a low [[concentration]] of waste [[chemical]]s they will be moved by [[Active Transport|active transport]] through the [[Cell Membrane|cell membrane]] out of the [[Cell (Biology)|cell]].

===About The Walls of the Alveoli as an Exchange Surface===
: When [[air]] is [[inhale]]d into the [[lung]]s [[Oxygen]] [[diffuse]]s from the [[air]] across the walls of the [[alveoli]] and into the [[Red Blood Cell|red blood cells]].
: Before [[air]] is [[exhale]]d out of the [[lung]]s [[Carbon Dioxide]] [[diffuse]]s out of the [[blood]] through the walls of the [[alveoli]] and into [[air]] in the [[lung]]s.
: The walls of the [[alveoli]] have several [[adaptation]]s to maximise the rate of [[diffusion]] across them:
:*The [[alveoli]] have thin walls to allow gas exchange to happen quickly.
:*[[Alveoli]] are in groups to make a large [[Surface Area|surface area]] in the [[lung]] for gas exchange.
:*The [[alveoli]] have a good [[blood]] supply to allow gas exchange with the [[blood]].
:*The walls of the [[alveoli]] are kept moist to allow [[gase]]s to [[dissolve]] into to the fluid for gas exchange with the [[blood]].

===About The Wall of the Small Intestines as an Exchange Surface===
: When food is consumed and [[digest]]ed the [[nutrient]]s can move across the walls of the [[Small Intestine|small intestine]] into the [[blood]] stream by [[diffusion]] or [[Active Transport|active transport]].
: The wall of the [[Small Intestine|small intestine]] is [[adaptation|adapted]] to allow the movement of [[nutrient]]s from the food into the [[blood]] stream in the following ways:
:*The [[Small Intestine|small intestine]] is long to give it a large [[Surface Area|surface area]].
:*The wall of the [[Small Intestine|small intestine]] is thin to provide a short distance for [[nutrient]]s to travel from food to the [[blood]] stream.
:*The wall of the [[Small Intestine|small intestine]] is covered in [[villi]] which are small folds, also increasing the [[Surface Area|surface area]].
:**The [[Villi]] have a wall only one cell thick so the [[nutrient]]s only have a short distance to [[Diffusion|diffuse]] into the [[blood]].
**[[Villi]] have [[Capillary|capillaries]] inside them for a good blood supply to allow for quick [[diffusion]] into the [[blood]].
:**[[Villi]] have a large [[Surface Area|surface area]] to allow quicker [[diffusion]].
:**The [[Cell (Biology)|cells]] in the walls of the [[villi]] have [[microvilli]] to provide an even bigger [[Surface Area|surface area]] for quicker [[diffusion]].
:***The [[microvilli]] have extra [[mitochondria]] to provide energy for [[Active Transport|active transport]].