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Encyclopedia > Flippase

Flippases (rarely, flipases) are enzymes located in the membrane responsible for aiding the movement of phospholipid molecules between the two leaflets that compose a cell's membrane (transverse diffusion). Although phospholipids diffuse rapidly in the plane of the membrane, their polar head groups cannot pass easily through the hydrophobic center of the bilayer, limiting their diffusion in this dimension. Phospholipid molecules that are synthesized in the cell are incorporated into the cytoplasmic face of the membrane, where flippases can transfer them to the exoplasmic face. Flippases require energy input in the form of ATP to carry out their function, often known as a flip-flop.[1] Ribbon diagram of the enzyme TIM, surrounded by the space-filling model of the protein. ... Image:CellWallDrawing. ... Two schematic representations of a phospholipid. ... A commonly-used example of a polar compound is water (H2O). ... In chemistry, hydrophobic or lipophilic species, or hydrophobes, tend to be electrically neutral and nonpolar, and thus prefer other neutral and nonpolar solvents or molecular environments. ... Biosynthesis is a phenomenon where chemical compounds are produced from simpler reagents. ... Organelles. ... ATP may refer to: Chemistry/Biochemistry Adenosine triphosphate, the universal energy currency of all living organisms Companies Alberta Theatre Projects, a major Canadian theatre company. ...


Many cells maintain asymmetric distributions of phospholipids in their cytoplasmic and exoplasmic membrane leaflets.[1] The loss of asymmetry, particularly the appearance of the anionic phospholipid phosphatidylserine on the exoplasmic face, can serve as an early indicator of apoptosis.[2] This effect has been observed in neurons as a response to exposure to amyloid beta peptides, thought to be a primary cause of the neurodegenerative effects of Alzheimer's disease.[3] An anion is an ion with negative charge. ... Phosphatidylserine is a nutrient found in fish, green leafy vegetables, soybeans and rice, and is essential for the normal functioning of the brain cell membrane. ... A cell undergoing apoptosis. ... Drawing by Santiago Ramón y Cajal of neurons in the pigeon cerebellum. ... Amyloid beta (Aβ or Abeta) is a protein fragment of 39-42 amino acids that is the main constituent of amyloid plaques in various neurological disorders, most prominently Alzheimers disease. ... Neurodegenerative disease is a condition which affects brain function. ...


References

  1. ^ a b Lodish, H, Berk A, Matsudaira P, Kaiser CA, Krieger M, Scott MP, Zipursky SL, Darnell J. (2004). Molecular Cell Biology, 5th, New York: WH Freeman.
  2. ^ Castegna A, Lauderback CM, Mohmmad-Abdul H, Butterfield DA. (2004). Modulation of phospholipid asymmetry in synaptosomal membranes by the lipid peroxidation products, 4-hydroxynonenal and acrolein: implications for Alzheimer's disease. Brain Res 1004(1-2):193-7.
  3. ^ Mohmmad Abdul H, Butterfield DA. (2005). Protection against amyloid beta-peptide (1-42)-induced loss of phospholipid asymmetry in synaptosomal membranes by tricyclodecan-9-xanthogenate (D609) and ferulic acid ethyl ester: implications for Alzheimer's disease. Biochim Biophys Acta 1741(1-2):140-8.

External links

  • Positions of lipid flippases in membranes

 
 

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