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Related Concept Videos

Membrane Fluidity01:23

Membrane Fluidity

Cell membranes are composed of phospholipids, proteins, and carbohydrates loosely attached to one another through chemical interactions. Molecules are generally able to move about in the plane of the membrane, giving the membrane its flexible nature called fluidity. Two other features of the membrane contribute to membrane fluidity: the chemical structure of the phospholipids and the presence of cholesterol in the membrane.Fatty acids tails of phospholipids can be either saturated or...
Membrane Fluidity01:26

Membrane Fluidity

Membrane fluidity is explained by the fluid mosaic model of the cell membrane, which describes the plasma membrane structure as a mosaic of components—including phospholipids, cholesterol, proteins, and carbohydrates—that gives the membrane a fluid character.
Mosaic nature of the membrane
The mosaic characteristic of the membrane helps the plasma membrane remain fluid. The integral proteins and lipids exist as separate but loosely-attached molecules in the membrane. The membrane is a relatively...
Asymmetric Lipid Bilayer01:35

Asymmetric Lipid Bilayer

Biological membranes show uneven distribution of different types of lipids in the inner and outer layers, resulting in transverse asymmetric membranes. The treatment of the erythrocyte membrane with the enzyme phospholipase confirmed the asymmetric nature of the lipid bilayer. The enzyme hydrolyzes lipids into fatty acids and hydrophilic groups. The phospholipase acts only on the outer layer of the membrane, while the inner layer remains intact. The phospholipase treatment resulted in 80%...
Assembly of the Lipid Bilayer in the ER01:28

Assembly of the Lipid Bilayer in the ER

Biological membranes are more than just a barrier separating cell cytoplasm from the outside environment. They are highly dynamic and help maintain the integrity and physiological stability of the cells as well as membrane-bound organelles. Membranes also play vital roles in cell-to-cell and intracellular communication.
A large chunk of any biological membrane is composed of phospholipids. These lipids have a heterogeneous distribution across different subcellular organelles and even between...
Membrane Asymmetry Regulating Transporters01:19

Membrane Asymmetry Regulating Transporters

Enzymes like flippase, floppase, and scramblase transfer phospholipids from one layer to another in the membrane, thereby affecting membrane asymmetry.
Flippase
Eukaryotic flippases are type-IV P-type ATPases or P4-ATPases belonging to P-type ATPase family proteins that are membrane-bound pumps involved in the ATP-mediated transport of ions and molecules across the membrane. Flippases flip specific phospholipids from the outer to the inner leaflet of a membrane. All P4-ATPases have one...
What are Lipids?01:31

What are Lipids?

Lipids function as structural components of cellular membranes, in addition to acting as energy reservoirs and signaling molecules. They are thus crucial to all living organisms.  The three biologically important classes of lipids are triglycerides, phospholipids, and steroids.
Non-Polar and Hydrophobic Characteristics of Lipids
Lipids are a structurally and functionally diverse group of hydrocarbons—compounds consisting of carbon and hydrogen atoms. The carbon-carbon and carbon-hydrogen bonds...

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A Fluorescence-based Assay of Phospholipid Scramblase Activity
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A Fluorescence-based Assay of Phospholipid Scramblase Activity

Published on: September 20, 2016

Lipid flippases and their biological functions.

T Pomorski1, A K Menon

  • 1Humboldt University Berlin, Institute of Biology/Biophysics, Invalidenstr. 43, 10115, Berlin, Germany. thomas.pomorski@rz.hu-berlin.de

Cellular and Molecular Life Sciences : CMLS
|November 15, 2006
PubMed
Summary

Lipid flippases are essential membrane proteins that maintain cell membrane asymmetry by transporting phospholipids. This review highlights recent advances in identifying and understanding these crucial flippase proteins and their functions.

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Last Updated: Jul 16, 2026

A Fluorescence-based Assay of Phospholipid Scramblase Activity
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Lipid Exchange Assay in Living Cells
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Area of Science:

  • Biochemistry
  • Cell Biology
  • Membrane Biology

Background:

  • Cell membranes possess distinct phospholipid compositions in their two leaflets.
  • This asymmetry is established and maintained by the bi-directional transport of lipids, known as flip-flop.
  • Specialized membrane proteins called lipid flippases facilitate this essential lipid transport.

Purpose of the Study:

  • To review recent progress in the identification and characterization of various lipid flippases.
  • To summarize the demonstrated biological functions of these flippases.
  • To provide an overview of the mechanisms by which flippases generate and maintain membrane lipid asymmetry.

Main Methods:

  • Literature review of recent research on lipid flippases.
  • Analysis of studies identifying and characterizing flippase proteins.
  • Synthesis of findings on the biological roles and mechanisms of flippases.

Main Results:

  • Identification of both energy-independent and ATP-dependent flippases.
  • Energy-independent flippases facilitate rapid phospholipid equilibration and glycoconjugate biosynthesis.
  • ATP-dependent flippases mediate net phospholipid transfer, crucial for membrane asymmetry and glycoconjugate synthesis (e.g., bacterial lipopolysaccharide).

Conclusions:

  • Lipid flippases are critical for establishing and maintaining transbilayer phospholipid asymmetry in cell membranes.
  • These proteins play vital roles in both lipid transport and the biosynthesis of complex molecules.
  • Continued research on flippases offers insights into fundamental cellular processes and potential therapeutic targets.