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Facilitated diffusion

 

 
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Facilitated diffusion
 
 
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Facilitated diffusion (or facilitated transport) is a process of diffusion
Diffusion

Molecular diffusion, often called simply diffusion, is a net transport of molecules from a region of higher concentration to one of lower concentration by random molecular motion....
, a form of passive transport
Passive transport

Passive transport means Motion biochemistrys and atomic or molecular substances across the The four main kinds of passive transport are diffusion, facilitated diffusion, filtration and osmosis....
 facilitated by transport protein
Transport protein

A membrane transport protein is a protein involved in the movement of ions, small molecules, or macromolecules, such as another protein across a biological membrane....
s. Facilitated diffusion is the spontaneous passage of molecules or ions across a biological membrane passing through specific transmembrane transport proteins. The facilitated diffusion may occur either across biological membrane
Biological membrane

A biological membrane or biomembrane is an enclosing or separating amphipathic layer that acts as a barrier within or around a cell . It is, almost invariably, a lipid bilayer, composed of a double layer of lipid-class molecules, specifically phospholipids and cholesterol, with occasional integral membrane protein intertwined, some o...
s 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
Cell membrane

The cell membrane is the interface between the cellular machinery inside the cell and the fluid outside.It is a semipermeable lipid bilayer found in all cell ....
 due to the hydrophobic
Hydrophobe

In chemistry, hydrophobicity refers to the physical property of a molecule that is repelled from a mass of water.Hydrophobic molecules tend to be non-polar and thus prefer other neutral molecules and nonpolar solvents....
 nature of the phospholipid
Phospholipid

File:Phospholipid.svgFile:phospholipid_structure.pngFile:Phosphatidyl-Choline.svgPhospholipids are a class of lipids and are a major component of all cell membranes....
s that make up the lipid bilayer
Lipid bilayer

A lipid bilayer is a thin membrane made of two layers of lipid molecules. These membranes are flat sheets that form a continuous barrier around cell ....
s.






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Encyclopedia


Facilitated diffusion (or facilitated transport) is a process of diffusion
Diffusion

Molecular diffusion, often called simply diffusion, is a net transport of molecules from a region of higher concentration to one of lower concentration by random molecular motion....
, a form of passive transport
Passive transport

Passive transport means Motion biochemistrys and atomic or molecular substances across the The four main kinds of passive transport are diffusion, facilitated diffusion, filtration and osmosis....
 facilitated by transport protein
Transport protein

A membrane transport protein is a protein involved in the movement of ions, small molecules, or macromolecules, such as another protein across a biological membrane....
s. Facilitated diffusion is the spontaneous passage of molecules or ions across a biological membrane passing through specific transmembrane transport proteins. The facilitated diffusion may occur either across biological membrane
Biological membrane

A biological membrane or biomembrane is an enclosing or separating amphipathic layer that acts as a barrier within or around a cell . It is, almost invariably, a lipid bilayer, composed of a double layer of lipid-class molecules, specifically phospholipids and cholesterol, with occasional integral membrane protein intertwined, some o...
s 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
Cell membrane

The cell membrane is the interface between the cellular machinery inside the cell and the fluid outside.It is a semipermeable lipid bilayer found in all cell ....
 due to the hydrophobic
Hydrophobe

In chemistry, hydrophobicity refers to the physical property of a molecule that is repelled from a mass of water.Hydrophobic molecules tend to be non-polar and thus prefer other neutral molecules and nonpolar solvents....
 nature of the phospholipid
Phospholipid

File:Phospholipid.svgFile:phospholipid_structure.pngFile:Phosphatidyl-Choline.svgPhospholipids are a class of lipids and are a major component of all cell membranes....
s that make up the lipid bilayer
Lipid bilayer

A lipid bilayer is a thin membrane made of two layers of lipid molecules. These membranes are flat sheets that form a continuous barrier around cell ....
s. Only small nonpolar molecules, such as oxygen
Oxygen

Oxygen no O2 produced; 2) O2 produced, but absorbed in oceans & seabed rock; 3) O2 starts to gas out of the oceans, but is absorbed by land surfaces and formation of ozone layer; 4-5) O2 sinks filled and the gas accumulates]]...
 can diffuse easily across the membrane. All polar molecules are transported across membranes
Cell membrane

The cell membrane is the interface between the cellular machinery inside the cell and the fluid outside.It is a semipermeable lipid bilayer found in all cell ....
 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 permease
Permease

The permeases are membrane transport proteins, a class of multipass transmembrane protein that facilitate the diffusion of a specific molecule in or out of the cell ....
s that change their conformation as the molecules are carried through, for example glucose
Glucose

Glucose , a monosaccharide also known as grape sugar, blood sugar, or corn sugar, is a very important carbohydrate in biology....
 or amino acids.

Non-polar molecules, such as retinol
Retinol

Retinol, the animal form of vitamin A, is a fat-soluble vitamin important in visual system and bone growth. It is also a Terpenoid. Retinol is among the most useable forms of vitamin A, which also include Retinal , Retinoic acid and retinyl ester ....
 or fatty acid
Fatty acid

In chemistry, especially biochemistry, a fatty acid is a carboxylic acid often with a long unbranched aliphatic tail , which is either saturation or Unsaturated compound....
s 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
Retinol binding protein

Retinol-binding proteins are a family of proteins with diverse functions. They are carrier proteins that bind retinol.Assessment of retinol-binding protein is used to determine visceral protein mass in nutritional studies related to health....
. 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
PEP group translocation

PEP group translocation, also known as the phosphotransferase system or PTS, is a distinct method used by bacteria for sugar uptake where the source of energy is from phosphoenolpyruvate....
 transportation.