Lipids. Lipids are soluble in nonpolar organic compounds They have a variety of structures and...
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Transcript of Lipids. Lipids are soluble in nonpolar organic compounds They have a variety of structures and...
Lipids
Lipids are soluble in nonpolar organic compounds
They have a variety of structures and functions
Fatty Acids Are Carboxylic Acid with Hydrocarbon Chains
The double bonds in naturally occurring fatty acids Have the cis configuration
Double bonds in naturally occurring unsaturated Fatty acids are separated by one methylene group
Polyunsaturated fatty acids have more than one double bond
Triacylglycerols
The three OH groups of glycerol are esterified with fatty acids
CH2 OH
CH OH
CH2 OH
R1 C OH
O
R2 C OH
O
R3 C OH
O
CH2 O
CH O
CH2 O
C
C
C
O
O
O
R1
R2
R3
glycerol fatty acidsa triacylglycerola fat or an oil
Fats are triacylglycerols existing as solid or semisolid state at room temperature
Oils are liquid triacylglycerols
Average composition of fatty acids %
Type Fat, Oil C14 C16 C18 Unsaturated
Animal Fats Butter 8-15 25-29 9-12 44-58
Lard 1-2 25-30 6-12 56-68
Beef tallow 2-5 24-34 15-30 31-59
Vegetable Oils
Olive 0-1 5-15 1-4 80-94
Peanut - 7-12 2-6 82-91
Corn 1-2 7-11 3-4 83-89
Soybean 1-2 6-10 2-4 84-91
Marine Oils Whale 5-10 10-20 2-5 65-83
Fish 6-8 10-25 1-3 64-83
C14 = myristic acid Unsaturated: Oleic (1)
C16 = palmitic acid Linoleic (2)
C18 = stearic acid Linolenic (3)
Phosphoacylglycerols
The terminal OH group of glycerol is esterified with phosphoric acid
They are the major components of cell membranes
The most common phosphoacylglycerols in membranes have a second phosphate ester linkage
Phosphoacylglycerols are classified as phospholipids
Phosphoacylglycerols form membranes by arrangingthemselves into a lipid bilayer
Saturated fatty acids decrease membrane fluidity because their hydrocarbon chains can pack closely together.
Unsaturated fatty acids have the opposite effect
Sphingolipids
They contain sphingosine instead of glycerol
They are the major lipid components in the myelin sheaths of nerve fiber
They are also found in membranes
Two of the Most Common Kinds of Sphingolipids
Prostaglandins are synthesized from arachidonic acid
They are responsible for regulating a variety of physiological responses
Prostaglandins
COOHH
H
postaglandin skeleton
Name in the format PGX, with X designating the functional groups of the five-membered ring
COOHH
H
O
HO OH
H
H
O
HO OH
COOH
H
HHO OH
COOH
HO
PGE1PGE2
PGF2
Naming Prostaglandins
Terpenes contain carbon atoms in multiples of five
They are made by joining together 5-carbon isoprene units
Terpenes
Oxygen-containing terpenes are sometimes called terpenoids
The Isoprene Rule
Squalene, a triterpene, is a precursor of steroid molecules
Lycopene and -carotene are tetraterpenes calledcarotenoids
Formation of geranyl pyrophosphate
Terpene Biosynthesis
Hormones are chemical messengers
Many hormones are steroids
All steroids contain a tetracyclic ring system
Steroids
Methyl groups at C-10 and C-13 are called angular methyl groups
The B, C, and D rings are trans fused
Thoseon the opposite side of the plane of the ring system are -substituents
Substituents on the same side of the steroid ring systemas the angular methyl groups are -substituents
The A and B rings are also trans fused in most naturallyoccurring steroids
Classification of Steroids
1. Sterols2. Bile Acids3. Hormones
Adrenocorticoid hormon Sex hormones
4. Steroid Glycosides
5. Steroid Alkaloids
6. Miscellaneous Steroids Toxines… etc…
Cholesterol Is a Steroid
bile acids (C24) CHOLESTEROL vitamin D (C27) h
pregnenolone (C21)
progesterone (C21)
glucocorticoids (C21) sex hormones mineralocorticoids (C21)
androgens (C19)
estrogens (C18)