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Lipids are a broad group of organic compounds which include 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 .
Waxes are organic compounds that characteristically consist of long aliphatic alkyl chains, although aromatic compounds may also be present. Natural waxes may contain unsaturated bonds and include various functional groups such as fatty acids, primary and secondary alcohols, ketones, aldehydes and fatty acid esters.
Example of an unsaturated fat triglyceride (C 55 H 98 O 6).Left part: glycerol; right part, from top to bottom: palmitic acid, oleic acid, alpha-linolenic acid. A triglyceride (from tri-and glyceride; also TG, triacylglycerol, TAG, or triacylglyceride) is an ester derived from glycerol and three fatty acids. [1]
Common Name Systematic Name Structural Formula Lipid Numbers Propionic acid: Propanoic acid CH 3 CH 2 COOH : C3:0 Butyric acid: Butanoic acid CH 3 (CH 2) 2 COOH : C4:0 Valeric acid
The fatty acids in wax esters derived from plants typically range from C12-C24, and the alcohols in plant waxes tend to be very long, typically C24-C34. [2] The fatty acids and fatty alcohols of wax esters from different marine animals show major differences. Wax esters of sperm whales contain C12 fatty acids and C14 fatty acid and alcohols.
In this sense, besides the triglycerides, the term would include several other types of compounds like mono-and diglycerides, phospholipids (such as lecithin), sterols (such as cholesterol), waxes (such as beeswax), [1] and free fatty acids, which are usually present in human diet in smaller amounts.
Codon–amino acids mappings may be the biological information system at the primordial origin of life on Earth. [128] While amino acids and consequently simple peptides must have formed under different experimentally probed geochemical scenarios, the transition from an abiotic world to the first life forms is to a large extent still unresolved ...
As a rule of thumb, the epidermal lipid matrix is composed of an equimolar mixture of ceramides (~50% by weight), cholesterol (~ 25% by weight), and free fatty acids (~15% by weight), with smaller quantities of other lipids also being present. [21] [22] The lipid barrier also protects against the entry of microorganisms. [20]