Lipids Flashcards
Lipids
organic compounds of biological origin that are soluble in organic solvents
Fatty acids (FA)
Simplest type of lipids
Building blocks of complex lipids
Long acyl chains ( confer hydrophobic character)
Can be saturated or unsaturated ( double bonds, influence the melting points)
IUPAC: number of C atoms+ -oic acid
Prostaglandins
Arachidonic acid is the precursor
Hormone function
Nomenclature: PGXn
Highly potent signaling molecules
NSAID
Inhibitors of enzymes that convert arachidonic acid into prostaglandins
Waxes
Of vegetal and animal origin
Esters between saturated FAs and long chain alcohols
Triacylglycerides (TAGs)
Storage molecules for fatty acids
Three FAs and a glycerol
Lipases
Enzymes that catalyze the hydrolysis of ester linkage
Saponification
Strong base-mediated hydrolysis (NaOH, KOH) leading to Na+/K+ salt of the FA. Soaps.
Phospholipids
Similar to triglycerides, but position 3 of glycerol makes an ester linkage to phosphoric acid, and this to one (amino)alcohol (ethanolamine, choline, serine) Phosphodiesteric linkage (similarity with DNA, RNA).
Sphingolipids
Sphingosine or dihydrosphingosine backbone
Ceramides
Sphingolipid
N-acyl sphingosines
Precursor of glycosphingolipids
Amide linkage with acyl chain
Sphingomyelin
Sphingosine is linked via an amide bond to a FA molecule and through an ester linkage to a phosphoric ester of the amino alcohol choline.
Cerebrosides
(Glycosphingolipid)
Important for cellular recognition (cell-cell contacts) and tissue immunity. A monosaccharide (galactose or glucose) is linked to the ceramide via a β glycosidic linkage
Gangliosides
Similar to cerebrosides, but contain two or more saccharidic units. Variable composition, apparently linked to specific functions.
• Characterized by the presence of an acid sugar called sialic acid.
Steroids
Compounds containing a common core structure composed by three six-membered rings and one five-membered ring
Cholesterol best known. Alkyl chain at C17 and hydroxyl at C3 make this molecule a sterol. Although minimal, the OH confers reactivity and partial hydrophilic character.
