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Diffusion

Definition

noun

1. The passive movement of molecules or particles along a concentration gradient, or from regions of higher to regions of lower concentration.

2. The spontaneous net movement of particles down their concentration gradient (i.e. difference in the concentrations of substances or molecules between two areas).

3. (Cell biology): a type of passive transport, therefore, it is a net movement of molecules in and out of the cell across the cell membrane along a concentration gradient.


Supplement

Unlike active transport, diffusion does not involve chemical energy. When molecules move (diffuse) via special transport proteins found within the cell membrane, it is called facilitated diffusion, otherwise it is only simple diffusion. An example of diffusion in biological system is diffusion of oxygen and carbon dioxide across the alveolar-capillary membrane in mammalian lungs.

Word origin: From Latin diffusionem (accusative of diffusio), from verb diffundere.
Related forms: diffusional (adjective).
Compare: active transport, osmosis.
See also: passive transport.


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Effects of SA; V ration on the rate of diffusion

... for me using biological terminology, conventions...? It would be appreciated. At least 1-2 sentences for the following 6 questions. 1. What is diffusion? - I googled this but unsure if it correct 2. What factors can affect diffusion? 3. why do cells require diffusion? 4. How do you think SA: ...

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by patrick987
Sun May 12, 2013 6:32 am
 
Forum: Cell Biology
Topic: Effects of SA; V ration on the rate of diffusion
Replies: 2
Views: 229

Re: Practical Examination (AS)

... the effect of surface area to volume ratio on the uptake of a substance. In addition, you will need to understand the following topics: · Diffusion · The effects of emphysema on lung function · Cigarette smoking and the risk of coronary heart disease · Size and surface area · Gas exchange" ...

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by Mahoganyjoint
Tue Apr 16, 2013 3:07 pm
 
Forum: General Discussion
Topic: Practical Examination (AS)
Replies: 4
Views: 842

Re: mutations and dependencies

... Gentry, whose 1982 report [Geophysical Research Letters 9(10):1129–1130] of high helium retentions in zircons was the basis for my RATE helium diffusion project. But none of us, despite frequent tries, have been able to publish papers with explicitly creationist conclusions.

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by jinx25
Tue Feb 19, 2013 6:13 pm
 
Forum: Evolution
Topic: mutations and dependencies
Replies: 17
Views: 4473

Refutation of Evolution theory

... static. If so, the organism must be contained by some kind of membrane otherwise its precious contents will drift away in the water due to natural diffusion or drifting of water due to temperature variations in the water from sunlight, etc. or from heat generated through its own power, or wind, ...

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by caveman
Sun Jan 20, 2013 9:12 am
 
Forum: Evolution
Topic: Refutation of Evolution theory
Replies: 8
Views: 3131

Chemiosmosis

... high proton concentration to an area of lower proton concentration. This could be harnessed to make ATP. He likened this process to osmosis, the diffusion of water across a membrane, which is called chemiosmosis. Thanks! :lol:

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by MarkHolland
Wed Dec 05, 2012 7:34 am
 
Forum: Cell Biology
Topic: Chemiosmosis
Replies: 5
Views: 2154
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