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Lipids
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Lipids Made up of C, H and O Can exist as fats, oils and waxes They are insoluble in water They are a good source of energy
(9 k cal / g) They are poor conductors of heat Most fats & oils are triglycerides
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Lipids Biomolecules that contain fatty acids or a steroid
nucleus. Soluble in organic solvents, but not in water. Named for the Greek word lipos, which means
“fat.” Extracted from cells using organic solvents.
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Triglycerides Formed by esterification (condensation reaction
between 3 fatty acids and glycerol)
Glycerol
H
C
H C
C
H
H
H
H
O
O
O
H
H
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Fatty acids Carboxyl group (-COOH) attached to a long non-polar hydrocarbon
chain (hydrophobic)
H
H
C
H
H
C
H
H
C
HC
O
O
H
C
HH
C
H
H
C
H
H
C
H
H
A saturated fatty acid (no double bonds)
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A polyunsaturated fatty acid
C
O
O
H
C
HH
C
H
H
C
H
H
C
H
C
H
H
C
H
H
C
H
H
A monounsaturated fatty acid
HH
C
O
O
H
C
HH
C C
C C H
C
H
H
C
H
HH H
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Esterification
C
O
O
H
C
HH
C
H
H
C
H
H
C
H
H
Glycerol Fatty acid
H
C
H C
C
H
H
H
H
O
O
O
H
H
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Esterification
C
O
O
H
C
HH
C
H
H
C
H
H
C
H
H
Glycerol Fatty acid
H
C
H C
C
H
H
H
H
O
O
O
H
H
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Esterification
C
OH
C
HH
C
H
H
C
H
H
C
H
Glycerol Fatty acid
C
H C
C
H
H
H
H
O
O
O
H
H
HO
H
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Esterification
C
OH
C
HH
C
H
H
C
H
H
C
H
C
H C
C
H
H
H
H
O
O
O
H
H
HO
H
Ester bond
water
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This happens three times to form a triglyceride
glycerol fatty acids
Esterification
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Phospholipids
One fatty acid can be replaced by a polar phosphate group
glycerol Hydrophobic fatty acids
hydrophilicphosphate
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Classification of Lipids Simple lipids Compound lipids (Complex) Derived lipids
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Simple lipids
The alcohol is glycerol
Oil (liquid at room temperature)
Fat (solid at room temperature)
Natural lipids need 3 F.As. and one molecule of
glycerol to form triglycerides + 3 H2O
A) Natural Lipids
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Simple lipids
Most natural waxes are esters derived from a fatty
acid and a long-chain alcohol
Main biological function of waxes: water barrier
Bee waxes are formed by honey bee and formed
from merioyl alcohol and palmitic acid.
B) Waxes
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Waxes Most natural waxes are esters derived from a fatty acid
and a long-chain alcohol
• Main biological function of waxes: water barrier
Myricyl cerotatePresent in beeswax
Cerotic acidA fatty acid
remove H2O
LeavesWax minimizes water evaporation
Myricyl alcoholLong chain alcohol
FeathersWax minimizes wetting
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Compound lipids
F.A + alcohol + other group Phospholipids (contain phosphate group) Glycolipids (contain carbohydrates) Lipoproteins (contain proteins)
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Derived lipids
Hormones Steroids
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Non-polar lipids (fats) are the principal molecules for energy storage.
Polar lipids (nitrogen and phosphorus containing) are components of biological membranes.
The steroid (class of lipids) (cholesterol) is found in biological membranes and used as a precursor for many hormones, bile and vitamin D
Miscellaneous lipids present only in minor quantities in the cell are involved as light-absorbing pigments (β-carotene, retinal), enzyme cofactors (vitamin K), signal molecules (prostaglandins), and electron carries.
Diversity in structure leads to a diversity in biological function
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Diversity in structure leads to a diversity in biological function
Used as a fuel reserve (when needed)
Provide body with essential fatty acids
Fats under skin (subcutaneous) are used as insulator and protecting and maintaining the body temperature.
Fats provide the protection and fixation of internal organs.
Lipoproteins enter in the formation of cell wall, muscles, mitochondria and microsomes.