Dictionary » D » Diffusion

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.


Please contribute to this project, if you have more information about this term feel free to edit this page



Results from our forum


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.

See entire post
by jinx25
Tue Feb 19, 2013 6:13 pm
 
Forum: Evolution
Topic: mutations and dependencies
Replies: 17
Views: 835

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, ...

See entire post
by caveman
Sun Jan 20, 2013 9:12 am
 
Forum: Evolution
Topic: Refutation of Evolution theory
Replies: 7
Views: 1127

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:

See entire post
by MarkHolland
Wed Dec 05, 2012 7:34 am
 
Forum: Cell Biology
Topic: Chemiosmosis
Replies: 5
Views: 1299

Why do neurones only have one axon?

... are anyway) with a substance called myelin this enables very fast transmission and has gaps at regular intervals called nodes of ranvier where diffusion of ions can occur. If we had lots of axons there would be loads of gaps and the action potentials or nerve impulses would become reduced and ...

See entire post
by Drredfrizzle
Sun Nov 11, 2012 7:46 pm
 
Forum: Human Biology
Topic: Why do neurones only have one axon?
Replies: 1
Views: 722

In and out cell help

for each you have to ask - does someone help them as in active transport? Do they move freely as in simple diffusion or do they use only restricted place to pass as in facilitated diffusion?

See entire post
by JackBean
Thu Nov 08, 2012 7:19 pm
 
Forum: General Discussion
Topic: In and out cell help
Replies: 1
Views: 526
View all matching forum results

This page was last modified 11:59, 17 June 2008. This page has been accessed 463,345 times. 
What links here | Related changes | Permanent link