BC 10: Lipids

fatty acids

HC derivatives. Their oxidation is very exergonic. 4-36C long, un/saturated, un/branched

common patterns of fatty acids

• most have even num of C in unbranched chain of 12-24C

• in monoUNsat fatacids, double bond us. between C9-10

• in polyUNsat fatacids, double bonds us. between 12 and 15, and us. separated by methylene group

• double bonds usually in cis config

[18:2(△^9,12)]

means 18 carbons with 2 double bonds between C9-10 and C12-13

polyunsaturated fatty acids (PUFAs)

contain >1 double bond in backbone.

• omega 3 fatacids: double bond between C3-4 relative to most distant carbon (omega)

• omega 6 fatacids: double bond between C6-7 relative to (oemga)

trialglycerols

simplest lipids made from fatacids - esters of glycerol.

• 3 fatacids each in ester link w single glycerol

• simple (one kind fatty acid) or mixed (2 or 3 diff fatacids)

• nonpolar, hydrophobic

• vertebrates store as lipid drops in adipocytes, plants store in seeds

solubility of fatty acids

• increase chain length = decrease solubility

• decrease double bond num = decrease solubility

• carboxylic acid group is polar and ionized at neutral pH

lipases

enzymes that catalyze hydrolysis of stored triacylglycerols, releasing fatacids for export to sites where they’re needed for fuel

trans fats

• raise level of triacylglycerols in blood

• raise level of LDL (bad) cholesterol and lower level of HDL

• increase body’s inflammatory response

4 general types of membrane lipids

1. phospholipids

2. glycolipids

3. archaeal tetraether lipids

4. sterols

phospholipids

hydrophobic regions composed of 2 fatacids joined to glycerol/sphingosine

glycolipids

contain simple sugar or complex oligosacc at polar ends

archaeal tetraether lipids

2 very long alkyl chains ether-linked to glycerol at both ends

sterols

compounds characterized by rigid system of 4 fused HC rings

glycerophospholipids (phosphglycerides)

membrane lipids where 2 fatty acids are attached in ester link to C1 and 2 of glycerol, and a highly polar/charged group is attached thru phosphodiester link to C3

• phosphate can bear neg, neut, or pos charge

• gen. contain C16 or C18 sat fatacids at C1, and/or C18 or C20 unsat fatacid at C2

ether lipids

one of two acyl chains is attached to glycerol in ether (rathern ester) link. chain maybe saturated and may contain double bond between C1-2 as in plasmalogens

platelet-activating factor

ether lipid that releases from basophils, stim. platelet aggregation & serotonin release. active in inflamm and allergic responses

galactolipids

member of glycolipid group that predominates in plant cells. 1 or 2 galactose residues connected by glycosidic link to C3 of 1,2-diacylglycerol

sphingolipids

large class of membrane phospholipids & glycolipids. At cell surfaces, are sites of bio recognition (neurons, human blood types)

• polar head group, 2 nonpolar tails

• no glycerol

• 1 molecule of longchain amino alcohol sphingosine (or derivative)

ceramide

sphingolipid compound resulting when fatacid’s attached in amide link to NH2 on C2 (struc similar to diacylglycerol; struc parents of all sphingolipids)

NEXT CARD SPHINGOMYELINS