Lecture 13 FATTY ACIDS and Steroids Convener Dr. Fawaz Aldabbagh.
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Transcript of Lecture 13 FATTY ACIDS and Steroids Convener Dr. Fawaz Aldabbagh.
Lecture 13
FATTY ACIDS and Steroids
Convener
Dr. Fawaz Aldabbagh
Lipids – water insoluble compoundsExcess carbohydrate (high energy foods) are stored as lipids, called fats.No definite structural grouping – include fats, oils, waxes, steroids + derivativesUses – Insulation, protection, help maintain correct body temperature, covering of nerve fibres + major structural material in cells
Two major groups – Saponifiable lipids and Non-Saponifiable lipids
Fatty Acids – naturally occurring long chain carboxylic acids
Unbranched carbon chain with an even number of carbon atoms
Long-chain fatty acids – 12-26 carbons are found in meat and fishMedium-chain fatty acids – 6-10 carbonsShort-chain fatty acids – less than 6 are found in dairy products
H
CH
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
O
OH
Hexadecanoic ac id (palmitic ac id)
COOH
H3C (CH2)14 C
O
OH
This is an example of a saturated fatty acid
COOH
Monounsatuarated
HH
Polyunsatuarated – have a carbon chain in which two or more DBs are present
COOH
linolenic acid
linoleic acid
COOH
These are Essential Fatty Acids
Fats and Oils are Esters
CH2
CH
CH2
OH
OH
OH
Glycerol
1,2,3-Propanetriol
Triacylglycerol (triglyceride)
CH2OC
CHO
CH2O
O
R
C R
O
C R
O
+ 3 NaOH
H2C
C
OH
OH
H2C OH
Glycerol
C
C
C
C R
OC R
O
O
R O Na
+
Sodium Carboxylate Soaps
H O
H
H O C
O
R
OH
H
H
H
H
H
H
H
H
H
H
axial
equatorial
cis-Decalin
equatorial
equatorial
trans-Decalin
H2C
H2CCH2
CH
H2C
CH2
CH2
CH2
H2CFused Bicyclic
Systems
cis is the same sidetrans opposite sides
H
H
axial
equatorial
axial
equatorial
Steroids can be isolated from the lipid fractions of animals and plants
Most show dramatic physiological effects when administered
A B
C DCH3
CH3
1
2
34
56
7
8
9
1112
1314
15
16
17
18
19
10
CH3
CH3
HOH
HH
H
H
Cholestanol
HO
all trans-junctions (equatorial-equatorial)
Cholestanolequatorial
CH3
H
CH3
H
H3C
CH3
CH3
HO Cholesterol
Isolated from nearly all animal tissuesGallstones are particularly rich in cholesterol Intermediate in the biosynthesis of other steroids
8 stereocenters28 = 256 possible isomeric forms
Sex Hormones1. The female sex hormones (estrogens)2. The male sex hormones (androgens)3. The pregnancy hormones (progrestins)
CH3
H
H H
O Progesterone
C O
CH3
CH3
CH3
H
H H
O Testosterone
OH
CH3
OHCH3
H
H H
HO
4 tonnes of sow overies gave 12 mg of estradiol
Estradiol
CH3
H H
HO
Ergosterol
CH3
CH3
H3C
H
CH3
H
HO
Vitamin D2
CH3
H3C
H
CH2
UV light
Sun-light helped to cure ricketsErgosterol was isolated from yeastAnd was found to be highly active