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A lipid bilayer is a biological membrane consisting of two layers of lipid molecules. Each lipid molecule, or phospholipid , contains a hydrophilic head and a hydrophobic tail. The tail regions, being repelled by water and slightly attracted to each other, congregate together.
The lipid bilayer is the barrier that keeps ions, proteins and other molecules where they are needed and prevents them from diffusing into areas where they should not be.
The lipid bilayer has been firmly established as the universal basis for cell-membrane structure. It is easily seen by electron microscopy, although specialized techniques, such as x-ray diffraction and freeze-fracture electron microscopy, are needed to reveal the details of its organization.
Most books mention that membranes have a typical "lipid bilayer," but why lipids, why should it be a bilayer, and how was this basic structure determined?
Overall, the lipid bilayer performs several key functions necessary for cell survival and proper functioning: Barrier function: By forming a semipermeable membrane, the lipid bilayer ensures that essential molecules such as ions, nutrients, and waste products can selectively enter and exit the cell.
(A) The plasma membrane of a cell is a bilayer of glycerophospholipid molecules. (B) A single glycerophospholipid molecule is composed of two major regions: a hydrophilic head (green) and ...
Lipids function as essential structural components of membranes, as signalling molecules, as chemical identifiers of specific membranes and as energy storage molecules.
The lipid bilayer is a universal component of all cell membranes. Its role is critical because its structural components provide the barrier that marks the boundaries of a cell. The structure is called a "lipid bilayer" because it is composed of two layers of fat cells organized in two sheets.
The lipid molecules are arranged as a continuous double layer about 5 nm thick (Figure 10-1). This lipid bilayer provides the basic fluid structure of the membrane and serves as a relatively impermeable barrier to the passage of most water-soluble molecules.
The function of the lipid bilayer membrane is mediated by the specific protein that is embedded in it. The proteins of the lipid bilayer function as pumps, channels, energy transducers, receptors, and enzymes.