Difference between revisions of "Diffusion"

Revision as of 08:45, 5 June 2019

Key Stage 3

Meaning

Diffusion is when particles spread from a region of high concentration to a region of low concentration.

About Diffusion

Diffusion can only happen in a fluid which means a liquid or a gas because the particles can move past each other.

Diffusion cannot happen in a solid because the particles are held in fixed positions.

In diffusion the particles always spread from a high concentration where there is lots of the substance, to a low concentration where there is less of the substance.

Diffusion stops when all substances are spread out equally and there is no longer a concentration gradient.


This diagram shows a high concentration of blue particles on the left separated from the red particles by a barrier. When the barrier is removed the blue particles diffuse to the area of lower concentration on the right. Diffusion continues until all particles are equally spread.


This animation shows a high concentration of red particles initially at the top. When diffusion begins the red particles spread to the area of lower concentration at the bottom. Diffusion continues until all particles are equally spread.

Key Stage 4

Meaning

Diffusion is when substances spread from a high concentration to a low concentration along the concentration gradient.

@@ Line 26: / Line 26: @@
 ===Meaning===
 [[Diffusion]] is when [[substance]]s spread from a high [[concentration]] to a low [[concentration]] along the [[Concentration Gradient|concentration gradient]].
-===About Diffusion across a Membrane===
-: [[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]].
-===Factors Affecting Diffusion across a Membrane===
-*[[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]].
-===Adaptations for Diffusion===
-: The [[lung]]s and [[Small Intestine|small intestine]] are specially [[Adaptation|adapted]] exchange surfaces that maximise the rate of [[diffusion]].
-====Lungs====
-The [[lung]]s must be able to [[Absorb (Biology)|absorb]] [[Oxygen]] into the [[blood]] and release [[Carbon Dioxide]] from the [[blood]] back into the [[lung]]s.
-: The [[lung]]s are [[Adaptation|adapted]] with thousands of [[alveoli]] which increase the surface area of the [[lung]]s.
-: The walls of the [[alveoli]] separating the [[air]] from the of [[blood]] are very thin.
-: The [[blood]] 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 Intestine====
-: The [[Small Intestine]] 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]].
-: 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]].
-: The walls of the [[villi]] separating the food from the [[blood]] are very thin.
-: The [[blood]] supply to the [[villi]]s is very good to constantly supply [[blood]] with little [[nutrients]] keeping a high [[Concentration Gradient|concentration gradient]] between the food and the [[blood]].

Difference between revisions of "Diffusion"

Revision as of 08:45, 5 June 2019

Contents

Key Stage 3

Meaning

About Diffusion

Key Stage 4

Meaning