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[2] [3] The most familiar type of animal sterol is cholesterol, which is vital to the structure of the cell membrane, and functions as a precursor to fat-soluble vitamins and steroid hormones. While technically alcohols, sterols are classified by biochemists as lipids ( fats in the broader sense of the term).
Cholesterol is the principal sterol of all higher animals, distributed in body tissues, especially the brain and spinal cord, and in animal fats and oils. [3] [4]Cholesterol is biosynthesized by all animal cells [citation needed] and is an essential structural and signaling component of animal cell membranes.
Membrane lipids are a group of compounds (structurally similar to fats and oils) which form the lipid bilayer of the cell membrane. The three major classes of membrane lipids are phospholipids, glycolipids, and cholesterol. Lipids are amphiphilic: they have one end that is soluble in water ('polar') and an ending that is soluble in fat ...
A biological membrane is a form of lamellar phase lipid bilayer. The formation of lipid bilayers is an energetically preferred process when the glycerophospholipids described above are in an aqueous environment. [2]: 333–4 This is known as the hydrophobic effect.
Their movement can be described by the fluid mosaic model, which describes the membrane as a mosaic of lipid molecules that act as a solvent for all the substances and proteins within it, so proteins and lipid molecules are then free to diffuse laterally through the lipid matrix and migrate over the membrane.
Cholesterol also helps regulate the activity of certain integral membrane proteins. Integral membrane proteins function when incorporated into a lipid bilayer, and they are held tightly to the lipid bilayer with the help of an annular lipid shell. Because bilayers define the boundaries of the cell and its compartments, these membrane proteins ...
Cross-sectional view of the structures that can be formed by phospholipids in an aqueous solution. A biological membrane, biomembrane or cell membrane is a selectively permeable membrane that separates the interior of a cell from the external environment or creates intracellular compartments by serving as a boundary between one part of the cell and another.
Illustration of a eukaryotic cell membrane Comparison of a eukaryotic vs. a prokaryotic cell membrane. The cell membrane (also known as the plasma membrane or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of a cell from the outside environment (the extracellular space).