结构生物化学Chapter16 Lipids and biological membranes
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EUnsaturated chains bend and pack in a less ordered way, with greater potential for motion.
Triglycerols (triglycerides)
u Triglycerols consist of a glycerol esterified with three fatty acids
membranes; «highly reduced forms of carbon; yield large amount
of energy upon oxidation in metabolism;
Lipid Classification
«Simple lipids: Fatty Acids and their simple esters – triacylglycerols and waxes
«Compound lipids: contain more than simple alcohols and fatty acids – glycerophosphatides, sphingolipids etc.
«Isoprenoid lipids: derived from isoprene – steroids, fat soluble vitamins, terpenes etc.
« Example of a terpene molecule:
Examples of terpene molecule
Steroids
« Based on a core structure consisting of three 6-membered rings and one 5-membered ring, all fused together;
« Sphingomyelins = ceramide + phospholipids (via 1-hydroxyl group)
« Glycosphingolipids = ceramide + β-linked sugar at the 1-hydroxyl moiety.
OH
OH
H H2C C CH
Chapter16 Lipids & biological membranes
Outline
@ Chemical structure and function of lipids
1. Simple lipids 2. Compound lipids 3. Isoprenoid lipids
@ Structure and function of biological membranes
Such an amphipathic lipid may be represented as at right.
O
O
H2C O C R2
R1 C O CH
O
H2C O P O X O
glycerophospholipid
"kink" due to double bond
polar non-polar
6
Fatty Acids
ü Fatty acids = carboxyl group + a long hydrocarbon chain ü Unstaurated fatty acids contain one or more double bonds
in hydrocarbon chains; Double bonds in fatty acids are usually have the cis configuration. ü Saturated fatty acids are single bonds in all carbon-carbon bonds; ü Most naturally occurring fatty acids have an even number of carbon atoms.
«Glycerophospholipids are a subclass of phospholipids;
«Glycerophospholipids are essential component of biological membranes;
Phosphatidic Acid and Phosphatides
Five glyerophospholipids
Phosphatidylcholine Phosphatidylserine
Phosphatidylinositol Phosphatidylethanolamine Diphosphatidylglycerol
(Cardiolipin)
Sphingolipids
– Oleic acid
18:1
– Linoleic acid
18:2
– α-linolenic acid 18:3 (9,12,15)
– γ-linolenic acid 18:3 (6,9,12)
– Arachidonic acid 20:4
– EPA 20:5 (5,8,11,14,17)
– DHA 22:6(4,7,10,13,16,19)
phosphocholine or phosphoethanolamine
a monosaccharide such as glucose or galactose
a complex oligosaccharide, including the acidic sugar sialic acid
Waxes
Terpenes
« Terpenes are a class of lipids from two or more molecules of 2-methyl-1,2-butadiene, or isoprene;
« All sterols (including cholesterol) and steroid hormones are terpene-based molecules
« Phosphatidic acid is the parent compound for the glycerol-based phospholipids;
« Phosphatidic acid consists of sn-glycerol-3-phosphate with fatty acids esterified at the 1and 2-positions;
OH
OH
H H2C C CH
H3N+ CH
NH CH
HC
O C HC
sphingosine
(CH2 )12
R
CH3 ceramide
(CH2 )12 CH3
CH 3
O
H3C
N+
H2 H2 CCO
P
O
CH 3
O
phosphocholine
H2C
sphingosine
OH H C CH
NH CH
O
fatty acid
« Essential Fatty Acids (EFA)
– Linoleic acid
– α- Linolenic Acid
Structural Consequences of Unsaturation
ESaturated chains pack tightly and form more rigid, organized aggregates (i.e., membranes);
1. Chemical components of biological membranes 2. Basic structure and properties of biological
membranes
@ transmembrane transport of substances
Lipids
«Lipids are biological compounds that are insoluble in water
R1 C O CH
O
H2C O P O X O
glycerophospholipid
Each glycerophospholipid includes w a polar region:
glycerol, carbonyl of fatty acids, Pi, & the polar head group (X) w 2 non-polar hydrocarbon tails of fatty acids (R1, R2).
S phingom yelin
C HC R (CH 2 )12
CH 3
Ether Glycerophospholipids
Examples of Sphingolipids
Sphingolipid sphingomyelin
cerebroside
ganglioside
Polar head group
Common Fatty Acids
« Saturated fatty acids:
– Lauric acid
12:0
– Myristic acid 14:0
– Palmitic acid
16:0
– Stearic acid
18:0
« Unsaturated fatty acids:
– Palmitoleic acid 16:1
«Hydrophobic barriers
– membrane constituents (phospholipids & glycoplipids)
« Functional
– protective coverings (waxes) – Buoyancy in aquatic organisms – regulatory properties e.g. coenzymes – hormones (steroids, prostaglandins, vitamins) – signalling e.g. odours
« Sphingosine forms the backbone of sphingolipids;
« Sphingosines are important components of biological membranes;
« Ceramide = sphingosine + fatty acid (via an amide link来自百度文库ge);
« Phosphatides are phosphatidic acid esterified with a hydroxyl-containing organic functional group.
O
O
H2C O C R2
R1 C O CH
O
H2C O P O
phosphatidate O
O
O H2C O C R2
Esters of long-chain alcohols with long-chain fatty acids
ü Highly insoluble ü Animal skin and fur are wax-
coated ü Leaves of many plants ü Bird feathers
u If all fatty acid chains are the same, the molecule is called triacylglycerol
Glycerophospholipids
«Glycerophospholipids=1, 2-diacylglycerols that has a phosphate group esterified at carbon 3;
-Are soluble in non-polar solvents
-Are a very heterogeneous group «Most Lipids are amphipathic because they have a
non-polar end and a polar end. «Lipids are a principle component of biological
* Fat soluble vitamins
*steroids
fatty acids
glycolipids phospholipids
* fatty acids absent
eicosanoids
triacylglycerols waxes
5
Functions
«Energy source
– storage compounds (triacyl glycerols)
Triglycerols (triglycerides)
u Triglycerols consist of a glycerol esterified with three fatty acids
membranes; «highly reduced forms of carbon; yield large amount
of energy upon oxidation in metabolism;
Lipid Classification
«Simple lipids: Fatty Acids and their simple esters – triacylglycerols and waxes
«Compound lipids: contain more than simple alcohols and fatty acids – glycerophosphatides, sphingolipids etc.
«Isoprenoid lipids: derived from isoprene – steroids, fat soluble vitamins, terpenes etc.
« Example of a terpene molecule:
Examples of terpene molecule
Steroids
« Based on a core structure consisting of three 6-membered rings and one 5-membered ring, all fused together;
« Sphingomyelins = ceramide + phospholipids (via 1-hydroxyl group)
« Glycosphingolipids = ceramide + β-linked sugar at the 1-hydroxyl moiety.
OH
OH
H H2C C CH
Chapter16 Lipids & biological membranes
Outline
@ Chemical structure and function of lipids
1. Simple lipids 2. Compound lipids 3. Isoprenoid lipids
@ Structure and function of biological membranes
Such an amphipathic lipid may be represented as at right.
O
O
H2C O C R2
R1 C O CH
O
H2C O P O X O
glycerophospholipid
"kink" due to double bond
polar non-polar
6
Fatty Acids
ü Fatty acids = carboxyl group + a long hydrocarbon chain ü Unstaurated fatty acids contain one or more double bonds
in hydrocarbon chains; Double bonds in fatty acids are usually have the cis configuration. ü Saturated fatty acids are single bonds in all carbon-carbon bonds; ü Most naturally occurring fatty acids have an even number of carbon atoms.
«Glycerophospholipids are a subclass of phospholipids;
«Glycerophospholipids are essential component of biological membranes;
Phosphatidic Acid and Phosphatides
Five glyerophospholipids
Phosphatidylcholine Phosphatidylserine
Phosphatidylinositol Phosphatidylethanolamine Diphosphatidylglycerol
(Cardiolipin)
Sphingolipids
– Oleic acid
18:1
– Linoleic acid
18:2
– α-linolenic acid 18:3 (9,12,15)
– γ-linolenic acid 18:3 (6,9,12)
– Arachidonic acid 20:4
– EPA 20:5 (5,8,11,14,17)
– DHA 22:6(4,7,10,13,16,19)
phosphocholine or phosphoethanolamine
a monosaccharide such as glucose or galactose
a complex oligosaccharide, including the acidic sugar sialic acid
Waxes
Terpenes
« Terpenes are a class of lipids from two or more molecules of 2-methyl-1,2-butadiene, or isoprene;
« All sterols (including cholesterol) and steroid hormones are terpene-based molecules
« Phosphatidic acid is the parent compound for the glycerol-based phospholipids;
« Phosphatidic acid consists of sn-glycerol-3-phosphate with fatty acids esterified at the 1and 2-positions;
OH
OH
H H2C C CH
H3N+ CH
NH CH
HC
O C HC
sphingosine
(CH2 )12
R
CH3 ceramide
(CH2 )12 CH3
CH 3
O
H3C
N+
H2 H2 CCO
P
O
CH 3
O
phosphocholine
H2C
sphingosine
OH H C CH
NH CH
O
fatty acid
« Essential Fatty Acids (EFA)
– Linoleic acid
– α- Linolenic Acid
Structural Consequences of Unsaturation
ESaturated chains pack tightly and form more rigid, organized aggregates (i.e., membranes);
1. Chemical components of biological membranes 2. Basic structure and properties of biological
membranes
@ transmembrane transport of substances
Lipids
«Lipids are biological compounds that are insoluble in water
R1 C O CH
O
H2C O P O X O
glycerophospholipid
Each glycerophospholipid includes w a polar region:
glycerol, carbonyl of fatty acids, Pi, & the polar head group (X) w 2 non-polar hydrocarbon tails of fatty acids (R1, R2).
S phingom yelin
C HC R (CH 2 )12
CH 3
Ether Glycerophospholipids
Examples of Sphingolipids
Sphingolipid sphingomyelin
cerebroside
ganglioside
Polar head group
Common Fatty Acids
« Saturated fatty acids:
– Lauric acid
12:0
– Myristic acid 14:0
– Palmitic acid
16:0
– Stearic acid
18:0
« Unsaturated fatty acids:
– Palmitoleic acid 16:1
«Hydrophobic barriers
– membrane constituents (phospholipids & glycoplipids)
« Functional
– protective coverings (waxes) – Buoyancy in aquatic organisms – regulatory properties e.g. coenzymes – hormones (steroids, prostaglandins, vitamins) – signalling e.g. odours
« Sphingosine forms the backbone of sphingolipids;
« Sphingosines are important components of biological membranes;
« Ceramide = sphingosine + fatty acid (via an amide link来自百度文库ge);
« Phosphatides are phosphatidic acid esterified with a hydroxyl-containing organic functional group.
O
O
H2C O C R2
R1 C O CH
O
H2C O P O
phosphatidate O
O
O H2C O C R2
Esters of long-chain alcohols with long-chain fatty acids
ü Highly insoluble ü Animal skin and fur are wax-
coated ü Leaves of many plants ü Bird feathers
u If all fatty acid chains are the same, the molecule is called triacylglycerol
Glycerophospholipids
«Glycerophospholipids=1, 2-diacylglycerols that has a phosphate group esterified at carbon 3;
-Are soluble in non-polar solvents
-Are a very heterogeneous group «Most Lipids are amphipathic because they have a
non-polar end and a polar end. «Lipids are a principle component of biological
* Fat soluble vitamins
*steroids
fatty acids
glycolipids phospholipids
* fatty acids absent
eicosanoids
triacylglycerols waxes
5
Functions
«Energy source
– storage compounds (triacyl glycerols)