Post on 18-Jan-2016
transcript
LipidsLipids
Broadly defined as naturally occurring non-polar compounds having simple functional groups.
Major Categories of LipidsMajor Categories of Lipids
Fats and Oils
• Biosynthesis of fatty acids Phospholipids Waxes Terpenes Steroids Prostaglandins
FatsFats
Esters of fatty (long chain carboxylic) acids Common are triacyl glycerols, which can be
hydrolyzed (saponified) into soaps:
CH2O2C
CHO2C
CH2O2C
NaOHaq.
CH2OH
CHOH
CH2OH
+ C13H27CO2 C15H31CO2 C17H35CO2Na Na Na+ +
Soap (mixture of salts of fatty acids):
O
CH2OC
CHOC
CH2OCO
O
Micelles: mode of action of soap
P
P
P
P
P
P
PP
P
P
P
P
P
P
P
P
P
PP
P
P
P
P
P
Na O
O
P
Soap (above) can be represented as:
Soap (and detergents) form spherical clusters(right) called micelles; micelles surroundand dissolve non-polar substances (oily stains) and render them “soluble.”
OilOil
HH22OO
HH22OO
HH22OO
HH22OOHH22OO
HH22OO
Oils (polyunsaturated fats)Oils (polyunsaturated fats)
CH2OC
O
CHO
CH2OC
CO
O
Presence of cis double bonds in oils makes it difficultfor the molecules to pack regularly in a solid structure; oils have lower melting points than fats, and are liquids at RT.
Biosynthesis of Fatty AcidsBiosynthesis of Fatty Acids
Repetitive applications of thio-Claisen
reactions; explains why most fatty acids
have an even number of carbon atoms
Enolization / Carboxylation of Acetyl Coenzyme AEnolization / Carboxylation of Acetyl Coenzyme A
CH2=CSCoA
OHC
O
OH+
(acetyl CoA, a 2 C unit) (enol form)
CH3CSCoA
O
CH2=CSCoA
OH
HOCCH2CSCoA
OO
(malonyl CoA)
Acylation of Malonyl Coenzyme A with 2 Carbon unitAcylation of Malonyl Coenzyme A with 2 Carbon unit
HOCCH2CSCoA
OO
HOCCH=CSCoA
OH
O
CH3C S synthase
O
(malonyl CoA)
CH3CCHCSCoA
O O
COHO
Enol form
Decarboxylation, Reduction, Dehydration and ReductionDecarboxylation, Reduction, Dehydration and Reduction
-CO2CH3CCH2CSCoA
O O
[H] (NADPH)
-H2O
CH3CHCH2CSCoA
OH O
CH3CH=CHCSCoA
O [H]
(NADPH)
CH3CH2CH2CSCoA
O
(a 4 Carbon unit)
CH3CCHCSCoA
O O
COHO
Acylation of Malonyl Co A with 4 carbon unitAcylation of Malonyl Co A with 4 carbon unit
HOCCH2CSCoA
OO
HOCCH=CSCoA
OH
O
CH3CH2CH2C S synthase
O
(malonyl CoA)
CH3CH2CH2CCHCSCoA
O O
COHO
(4 carbon unit)
Conversion to 6 carbon unitConversion to 6 carbon unit
CH3CH2CH2CCHCSCoA
O O
COHO
decarboxylation,reduction of C=Odehydrationreduction of C=C
CH3CH2CH2CH2CH2CSCoA
O
(6 carbon unit)
Acylation of Malonyl Co A with 6 carbon unitAcylation of Malonyl Co A with 6 carbon unit
CH3CH2CH2CH2CH2C
O
S synthase
CH3CH2CH2CH2CH2CCHCSCoA
O O
COHO
(malonyl CoA)
HOCCH=CSCoA
OH
O
HOCCH2CSCoA
OO (6 carbon unit)
Conversion to 8 carbon unit...etc.Conversion to 8 carbon unit...etc.
CH3CH2CH2CH2CH2CH2CH2CSCoA
O
reduction of C=Odehydration,reduction of C=C
decarboxylation,
CH3CH2CH2CH2CH2CCHCSCoA
O O
COHO
(8 carbon unit)
Common Saturated Fatty AcidsCommon Saturated Fatty Acids
CO2H
CO2H
CO2H
C14 Myristic Acid
C16 Palmitic Acid
C18 Stearic Acid
Common Unsaturated Fatty Acids
C
O
OH
Palmitoleic
C
O
OH
Oleic
Linoleic
C
O
OH
Polyunsaturated Fatty Acids
Polyunsaturated fatty acids (PUFAs) include those having two and three double bonds.
Omega-3 fatty acids are those unsaturated fatty acids that have a double bond between the third and fourth carbon from the end of the carbon chain (opposite the CO2H group).
A common omega-3 fatty acid found in fish oil is linolenic acid:
Omega-3 fatty acids are considered beneficial for brain function.
C
O
OH
1
2
3 6 9
Composition of Fats and Oils
lauric myristic palmitic stearic oleic linoleic
C12 C14 C16 C18 C18(1) C18(2)
Animal FatsLard - 1 25 8 50 10Beef Fat - - 27 14 50 3Butter Fat 2 10 29 10 27 5Human Fat 1 3 25 8 46 10Whale Blubber - 8 12 3 35 10
Vegetable OilsCoconut oil 48 18 11 2 7 1Corn oil - 1 10 3 45 35Olive oil - 1 7 3 82 6Peanut oil - - 7 5 58 24Soybean oil - - 10 2 29 51
Fats and Oils in Nuts
Nut g. prot./oz. g. fat/oz % sat’d % MUFAs % PUFAs
Walnuts 4 18 10 15 75
Almonds 6 14 10 65 25
Hazelnuts 4 17 9 77 14
Cashews 4 13 21 62 17
Macadamia 2 22 16 76 8
Pecans 3 20 9 53 28
Peanuts 7 14 16 52 32
Phospholipids
Phospholipids are long-chain fatty esters of glycerol also containing a phosphoric acid derivative.
They contain a glycerol backbone, like fats and oils, but they have a phosphate group with an ionic alkyl ammonium group also attached.
Representative Phospholipids
CH2O
CO H
CH2O P
O
O
O CH2CH2N(CH3)3
C R
O
C
O
R'
CH2O
CO H
CH2O P
O
O
O CH2CH2NH3
C R
O
C
O
R'
Phosphatidylcholine (lecithin)
Phosphatidylethanolamine (cephalin)
CH2
CO H
CH2O P
O
O
O CH2CH2N(CH3)3
C
OOC
O
Phospholipids…
P
Can be represented as:
CH2
CO H
CH2O P
O
O
O CH2CH2N(CH3)3
C
OOC
O
Lipid Bilayer of Cell Membranes
P P P P P P P
P P P P P P P
Cell membrane
Outside the cell (aqueous)
Inside the cell (aqueous)
WaxesWaxes
Long chain esters of long chain fatty acids
CH3(CH2)mCO2(CH2)nCH3
m = 8 - 18 n = 15 - 35
Waxes:
O
O
(present in beeswax)
TerpenesTerpenes
Derived biosynthetically from a branched five carbon unit, isopentenyl pyrophosphate:
OP
OP
O
OO
O O
isopentyl pyrophosphate isopreneisopentenyl pyrophosphate
Terpenes...Terpenes...
Common monoterpenes (C10):
OH
geraniol
CH2OH
CHO
citral
OH
menthol
Some more common terpenes
zingiberene (ginger)a sesquiterpene; 15 Cs
limonene(lemons)
citronellal(oil of citronella)
O
H
O
H
SteroidsSteroids
Involved in regulatory processes and in sexual characteristics and functions
Common steroids include cholesterol, estradiol, testosterone, estrone and progesterone
CH3
CH3
R
CH3
CH3
R
AA BB
CC DD
AA BBCC
DD
Some Common Steroids
CH3
CH3
H
HH
O
HOH
CH3
CH3
H
HH
HO
O
CH3
H
HH
HO
O
testosterone androsterone
estrone
H
HH
HO
OHCH3
estradiol
…More Common Steroids
H
CH3
H
HH
O
C CHOH
progesterone
CH3
CH3
H
HH
O
CO CH3
norethrindroneethynylestradiol
CH3
H
HH
HO
C CHOH
CH3
CH3
H
HH
HO
H
cholesterol
…More Common Steroids
CH3
CH3
H
HH
O
O OHC
O CH2OH
cortisone
CH3
CH3
H
HH
HO
H
CO2H
HOH
OH
cholic acid
Prostaglandins
C20 carboxylic acids that contain a 5-member ring and have two long side chains.
They were first isolated from prostate glands of sheep, but now they are known to have widespread distribution among tissues, and to exhibit an extraordinarily wide range of biological effects.
Representative Structures
Biosynthetic source: Biosynthetic source: arachidonic acidarachidonic acid
Prostaglandin E1 (PGE1) Prostaglandin F2 (PGF2)
CO2H
CO2H
HO H
H
HHO
O
CO2H
HO H
H
HHO
HO H
Some Varied Biological Effects of Prostaglandins
Lower blood pressure Affect clotting of blood Lower gastric secretions Promote inflammation (countered by aspirin,
which inhibits PG biosynthesis) Affect reproductive systems Stimulate uterine contractions during childbirth
Final ExamFinal Exam
Review:
A review session is scheduled for class on Monday, April 30 in DO 202. Bring questions, and bring the last 4 sheets of the Course-Pack.
Final Exam:
Monday, May 7, 8:00 am – 11:00 am
(Dobo Hall, Room 202)