Facilitated diffusion

Facilitated diffusion

Facilitated diffusion (or facilitated transport) is a process of diffusion, a form of passive transport facilitated by transport proteins. The facilitated diffusion may occur either across biological membranes or through aqueous compartments of an organism.

Polar molecules and charged ions are dissolved in water but they can not diffuse freely across cell membranes due to the hydrophobic nature of the lipids that make up the lipid bilayers. Only small nonpolar molecules, such as oxygen can diffuse easily across the membrane. All polar molecules should be transported across membranes by proteins that form transmembrane channels. These channels are gated so they can open and close, thus regulating the flow of ions or small polar molecules. Larger molecules are transported by transmembrane carrier proteins, such as permeases that change their conformation as the molecules are carried through, for example glucose or amino acids.

Non-polar molecules, such as retinol or fatty acids are poorly soluble in water. They are transported through aqueous compartments of cells or through extracellular space by water-soluble carriers as retinol binding protein. The metabolites are not changed because no energy is required for facilitated diffusion. Only permease changes its shape in order to transport the metabolites. The form of transport through cell membrane which modifies its metabolites is the group translocation transportation.

Facilitated Diffusion- Another type of Passive Transport that uses a carrier protein.


Wikimedia Foundation. 2010.

Игры ⚽ Поможем сделать НИР

Look at other dictionaries:

  • facilitated diffusion — Diffusion across the plasma membrane that is aided by a carrier …   Dictionary of microbiology

  • facilitated diffusion — diffusion across a plasma membrane or other biological membrane in which the molecules to be transported form complexes with specific transport proteins (uniporters) that shuttle them across the membrane down the concentration gradient and… …   Medical dictionary

  • facilitated diffusion — (= passive transport) A process by which substances are conveyed across cell membranes faster than would be possible by diffusion alone. This is generally achieved by proteins that provide a hydrophilic environment for polar molecules throughout… …   Dictionary of molecular biology

  • Diffusion (disambiguation) — Diffusion is a time dependent random process causing a spread in space. Diffusion may also refer to: In physical sciences Molecular diffusion, spontaneous dispersion of mass (distinct from migration, caused by an external force) Conduction of… …   Wikipedia

  • Diffusion — This article is about the generic concept of the time dependent random process. For other uses, see Diffusion (disambiguation). Diffusion describes the spread of particles through random motion from regions of higher concentration to regions of… …   Wikipedia

  • Diffusion of technology in Canada — This article outlines the history of the diffusion or spread of technology in Canada. Technologies chosen for treatment here include, in rough order, transportation, communication, energy, materials, industry, public works, public services… …   Wikipedia

  • diffusion — 1. The random movement of molecules or ions or small particles in solution or suspension under the influence of brownian (thermal) motion toward a uniform distribution throughout the available volume; the rate is relatively rapid among liquids an …   Medical dictionary

  • Colloid-facilitated transport — designates a transport process by which colloidal particles serve as transport vector [1] of diverse contaminants in the surface water (sea water, lakes, rivers, fresh water bodies) and in underground water circulating in fissured rocks [2]… …   Wikipedia

  • Passive transport — means moving biochemicals and other atomic or molecular substances across membranes. Unlike active transport, this process does not involve chemical energy, because, unlike in an active transport, the transport across membrane is always coupled… …   Wikipedia

  • Membrane potential — Differences in concentration of ions on opposite sides of a cellular membrane lead to a voltage called the membrane potential. Many ions have a concentration gradient across the membrane, including potassium (K+), which is at a high inside and a… …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”