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Diffusion is a mechanism used to transport materials across cell membranes, using no energy (ATP). | Diffusion is a mechanism used to transport materials across [[cell membranes|cell membranes]], using no energy ([[ATP|ATP]]). | ||
There are three types of diffusion: | There are three types of diffusion: | ||
*simple diffusion | *simple diffusion | ||
*facilitated transport | *facilitated transport | ||
*co-transport | *co-transport<br> | ||
=== Simple Diffusion === | |||
<u></u>The movement of ions and molecules from an area of high concentration to a low concentration across a cell membrane. | |||
[[Molecules|Molecules]] which are transported by simple diffusion include: | |||
*[[oxygen|oxygen]] | |||
*[[carbon dioxide|carbon dioxide]] | |||
*oxygen | |||
*carbon dioxide | |||
*steroid hormones<br> | *steroid hormones<br> | ||
=== Facilitated Transport === | |||
<u></u>Facilitated diffusion is the diffusion of ions, [[water|water]] or hydrophilic molecules across a membrane with the help of channel [[proteins|proteins]]. Of these channel proteins there are two types; gated and non-gated channels.<br> | |||
Molecules which are transported via facilitated diffusion include: | |||
Molecules which are transported via facilitated diffusion include: | |||
*[[glucose|glucose]] | |||
*[[amino acids|amino acids]] | |||
*[[water|water]] | |||
*some [[ions|ions]] <ref>LODISH, H et al. (2008) Molecular Cell Biology, 6th ed. p439-440. New York: W.H. Freeman and Company</ref> | |||
=== References === | |||
<references /> | <references /> | ||
Revision as of 15:06, 2 December 2011
Diffusion is a mechanism used to transport materials across cell membranes, using no energy (ATP).
There are three types of diffusion:
- simple diffusion
- facilitated transport
- co-transport
Simple Diffusion
The movement of ions and molecules from an area of high concentration to a low concentration across a cell membrane.
Molecules which are transported by simple diffusion include:
- oxygen
- carbon dioxide
- steroid hormones
Facilitated Transport
Facilitated diffusion is the diffusion of ions, water or hydrophilic molecules across a membrane with the help of channel proteins. Of these channel proteins there are two types; gated and non-gated channels.
Molecules which are transported via facilitated diffusion include:
- glucose
- amino acids
- water
- some ions [1]
References
- ↑ LODISH, H et al. (2008) Molecular Cell Biology, 6th ed. p439-440. New York: W.H. Freeman and Company