Journal of Clinical Nutrition & Dietetics

Description

Triglyceride and triacylglycerol are sometimes used interchangeably. All three of glycerol's hydroxyl groups are esterified in these molecules, usually by distinct fatty acids. Most of the fat that is stored in animal tissues is held in these lipids, which act as an energy storage. The first stages of fat digestion include the dissolution of triglyceride ester linkages and the liberation of glycerol and fatty acids from fat tissue. Glycosylglycerols, which are glycolipid subclasses in their own right, are identified by the presence of one or more sugar residues bound to glycerol through a glycoside bond. The seminolipid from mammalian sperm cells and the digalactosyldiacylglycerols present in plant membranes are two examples of structures in this group.

Nutritional substances

Lipids also encompass molecules such as fatty acids and their derivatives including tri-, di-, monoglycerides and phospholipids as well as other sterol-containing metabolites like cholesterol. While humans and other warm-blooded animals employ various biosynthetic pathways both to break down and to synthesize lipids, some essential lipids cannot be produced in this manner and must be obtained from the diet. Years later, Berthelot, one of Pelouze's students, synthesized tristearin and tripalmitin by reacting nearly equivalent fatty acids with glycerol in the presence of gaseous hydrogen chloride at high temperature. In 1827, William recognized fatty oils as vital nutritional substances alongside protein and carbohydrates for humans and animals. In chemistry and biochemistry, a lipid is a biomolecule that is soluble in nonpolar solvents. Nonpolar solvents are hydrocarbons used to dissolve other hydrocarbon lipid molecules that do not dissolve in water, including fatty acids, waxes, sterols, fat-soluble vitamins (A, D, E and K), monoglycerides, diglycerides, triglycerides and phospholipids. Lipids serve functions such as storing energy, signaling and acting as structural components of cell membranes. Lipids have applications in the cosmetic and food industries as well as in nanotechnology. For a century, chemists regarded fats as simply basic lipids made of fatty acids and glycerol, but new structures were described later. Theodore discovered phospholipids in mammalian brain and hen egg, termed by him as lecithins. They consist of a hydrocarbon chain ending with a carboxylic acid group; this arrangement endows the molecule with a polar, hydrophilic end and a nonpolar, hydrophobic end that is insoluble in water.

Categories of organic lipids

The fatty acid structure is one of the most fundamental categories of organic lipids and is often used as a building block of more complex lipids. The carbon chain, typically between four and 24 carbons long, may be saturated or unsaturated and may be attached to functional groups containing oxygen, incandescent lamp, nitrogen and sulfur. If a fatty acid contains a double bond, there is the possibility of either a cis or trans geometric isomerism, which significantly affects the molecule's structure. Cis-double bonds cause the fatty acid chain to bend, an effect that is compounded with additional double bonds in the chain. Three double bonds in 18-carbon linolenic acid, the most abundant fatty acyl chains of plant thylakoid membranes, render these membranes highly fluid despite organic lowtemperatures and also make linolenic acid give dominant sharp peaks in high-resolution spectra of chloroplasts. This, in turn, plays a significant role in the structure and function of cell membranes. Most naturally occurring fatty acids are of the cis configuration, although the trans configuration exists in some natural and partially hydrogenated fats and oils. Other major lipid classes in the fatty acid category are the fatty esters and fatty amides.