BIOC 503 - Complex Lipids

glycerolipids

Lipids with a glycerol backbone

• triacylglycerols (storage fat, neutral lipids)

• glycerophospholipids (major mammal membrane lipids)

• galactolipids (major plant membrane lipids)

sphingolipids

lipids molecule with a sphingosine backbone instead of glycerol backbone. Ceramide for basic structure.

• ceramides

• sphingophospholipids

• glycosphingolipids

• gangliosides

cholesterol

lipids with a sterol nucleus backbone

• precursors to hormones

triacylglycerols

glycerolipid (glycerol backbone) used as fat storage

• look at ALL 3 fatty acid chains to figure out if it is solid/liquid at room temp

glycerophospholipids

derivatives of phosphatidic acid (PA)

• glycerol backbone with a phosphate group in 3rd position (sometime linked to specific headgroup)

• PA , PE, PC, PS, PG, PI

PA

phosphatidic acid

• hydrogen head group

• -1 charge

PE

phosphatidylethanolamine 

• ethanolamine head group

• 0 charge

PC

phosphatidylcholine

• choline head group

• 0 charge

PS

phosphatidylserine

• serine head group

• 1 charge

PG

phosphatidylglycerol

• glycerol head group

• -1 charge

PI

phosphatidylinositol 4,5 biphosphate

• inositol biphosphate head group

• -4 charge

cardiolipin

glycerophospholipid with a phosphatidylglycerol head group

• found in heart

• -2 charge

PIP2

signaling molecule made by phosphorylating PI at position 1 & 2 of head group

• can be broken down in DAG and IP3

phospholipase A1

aka PLA1

break ester linkage in position 1

phospholipase A2

aka PLA2

break ester-linkage in position 2

phospholipase C

aka PLC

break phosphodiester linkage attaching phosphate group of glycerophospholipids attaching phosphate to glycerol backbone in position 3

phospholipase D

aka PLD

break phosphodiester linkage of glycerophospholipids linking phosphate to head group in position 3

plasmalogens

glyceryl ethers

• abundant in the heart and brain

• type of glycerophospholipids

• ester-linked alkene in position 1

• choline group linked to phosphate in 3rd position

• CANNOT be cleaved by PLA1 and PLA2 thus providing some stability to membrane

platelet-activating factor

aka PAF

• type of GLYCEROPHOSPHOLIPIDS

• acetyl ester in 2nd position

• choline linked to phosphate in 3rd position

• WATER SOLUBLE due to acetic acid bound in 2nd position and the polar head group

• extracellular factor

galactolipids

phosphate-free glycerolipids

• sugar (galactose) in 3rd position instead of phosphate

• glycosidic linkage

• abundant in plants (MGDG & DGDG)

sulfolipid

modified galactolipid in which the sugar residue in 3rd position has a sulfur group attached to it

sphingosine

18 carbons amino alcohol lipid with hydrophobic chain serving as backbone for sphingolipids

• amino group used to attach fatty acid using amide linkages (forming ceramides)

ceramide

lipid made of sphingosine backbone with a fatty acid attached to what used to be the amino group using amide linkages

• general structure for sphingolipids aka small head group

• modified head group = different sphingolipids

sphingomyelin

lipid structured like ceramide (sphingosine + fatty acid attached at amino group position) with a phosphocholine head group 

• used for membrane of myelin sheath

• SPHINGOPHOSPHOLIPID

cerebroside

neutral glycosphingolipid with glucose as head group (position 1)

globoside

neutral glycosphingolipid with di-, tri-, or tetrasacharide as head group (position 1)

Ganglioside

category of sphingolipids containing sialic acid as head group and thus being negatively (-) charged at neutral pH

• found in ganglion cells

• sialic acid = sugar alcohol

oligosaccharides linked to the negatively charged sialic acid; membrane lipids located on the outer layer of membrane acting as a virus receptor

outer

glycosphingolipids are always located on the __ leaflet of the membrane (sugar residues stick out on the outside and act as signaling molecules)

significance of glycosphingolipids

• blood group markers

• differentiation markers

• transformation markers

• ligands

• receptors

glycosphingolipids

sphingolipids containing one or more saccharides, membrane lipids located on the outer layer, determine blood group

• include gangliosides, cerebrosides, & globosides

cholesterol

27 carbons compound based on a sterol nucleus which is made of a 4 fused rings structure (three 6-membered rings, and one 5-membered ring) which limits carbon-carbon rotation

• highly hydrophobic molecules due to LARGE hydrophobic body even though it has a small headgroup

• small headgroup makes molecule charged at neutral pH

• precursor to a lot of steroid hormones and prostaglandins, bile acids, bile salts, & vitamin D

• very little solubility due to small headgroup aka -OH group

cholesteryl ester

storage form of cholesterol which has been esterified

• fully hydrophobic and thus transported into the core of proteins

• replacing -OH head group by fatty acid = esterification

• completely insoluble