Lipid

Structures of some common lipids. At the top are cholesterol[1] and oleic acid.[2]: 328  The middle structure is a triglyceride composed of oleoyl, stearoyl, and palmitoyl chains attached to a glycerol backbone. At the bottom is the common phospholipid phosphatidylcholine.

Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids include storing energy, signaling, and acting as structural components of cell membranes.[3][4] Lipids have applications in the cosmetic and food industries, and in nanotechnology.[5]

Lipids may be broadly defined as hydrophobic or amphiphilic small molecules; the amphiphilic nature of some lipids allows them to form structures such as vesicles, multilamellar/unilamellar liposomes, or membranes in an aqueous environment. Biological lipids originate entirely or in part from two distinct types of biochemical subunits or "building-blocks": ketoacyl and isoprene groups.[3] Using this approach, lipids may be divided into eight categories: fatty acyls, glycerolipids, glycerophospholipids, sphingolipids, saccharolipids, and polyketides (derived from condensation of ketoacyl subunits); and sterol lipids and prenol lipids (derived from condensation of isoprene subunits).[3]

Although the term "lipid" is sometimes used as a synonym for fats, fats are a subgroup of lipids called triglycerides. Lipids also encompass molecules such as fatty acids and their derivatives (including tri-, di-, monoglycerides, and phospholipids), as well as other sterol-containing metabolites such as cholesterol.[6] Although humans and other mammals use various biosynthetic pathways both to break down and to synthesize lipids, some essential lipids cannot be made this way and must be obtained from the diet.

  1. ^ Cite error: The named reference Maitland_1998 was invoked but never defined (see the help page).
  2. ^ Cite error: The named reference Stryer_2007 was invoked but never defined (see the help page).
  3. ^ a b c Cite error: The named reference Fahy_2009 was invoked but never defined (see the help page).
  4. ^ Cite error: The named reference Subramaniam_2011 was invoked but never defined (see the help page).
  5. ^ Cite error: The named reference Mashaghi_2013 was invoked but never defined (see the help page).
  6. ^ Cite error: The named reference Michelle_1993 was invoked but never defined (see the help page).

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