Lipids
Composed of C, H and few O
Basic unit is fatty acid (glyceride)
Triglyceride is the major form of lipid = 3 fatty acids
Fats and oils
Monounsaturated Fatty Acids
Polyunsaturated Fatty Acids
Saturated Fatty Acids
Essential Fatty Acids
Energy yielding (9 kcal /gm)
Sources of Dietary Lipids
Properties of Lipids
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Do not readily dissolve in water
Fats are solid at room temperature
Oils are liquid at room temperature
Triglycerides are the main form of
lipids in food and body (storage)
• Energy dense (9 kcal /gm)
The building block of lipids are fatty acids
H H H H H H H H H H H H H H H HHO
H-C--C--C--C--C--C--C--C--C--C--C--C--C--C--C--C--C-C-OH
H H H H H H H H H H H H H H H H H
omega end
alpha end
Note that all carbons have two hydrogens – this is a
fully saturated fatty acid.
Triglycerides
H
O
H--C--OH
HO-C-R
H
H--C--O--C-- R + H2O
O
H--C--OH
+
HO-C-R
O
H--C--O--C-- R + H20
O
H--C--OH
HO-C-R
H
Glycerol
3 H20
O
O
H--C--O--C-- R + H20
H
+ 3 FA’s
(Ester bond)
Triglyceride +
Triglycerides
H
H
H--C--OH
Fatty Acid
H--C--OH
+
Fatty Acid
H--C--O--C-- Fatty Acid
O
H--C--O--C-- Fatty Acid
Fatty Acid
H--C--OH
H
O
O
H--C--O--C-- Fatty Acid
H
esterification
desterfication
Monounsaturated Fatty Acid Structure
H H H H H H H H
H H H H H H H O
H-C--C--C--C--C--C--C--C--C=C--C--C--C--C--C--C--C--C-OH
H H H H H H H H H H H H H H H H H
omega end
end
alpha
When two Hs are lost from two adjacent Carbons, a
double bond is formed. This is an unsaturated fatty
acid.
Polyunsaturated Fatty Acid Structure
H H H H H
H
H H H H H HH O
H-C--C--C--C--C--C=C--C--C=C--C--C--C--C--C--C--C--C-OH
H H H H H H H H H H H H H H H H H
omega end
end
Two or more double bonds results in a
polyunsaturated fatty acid.
alpha
The more double bonds, the lower the melting
point of a fat/oil
• Beef fat or lard has a large amount of saturated fatty
acids that are long. It is solid at room temperature.
• Butter has about the same number of saturated as
unsaturated fatty acids. Butter is beginning to melt at
room temperature.
• Vegetable oil is 100% unsaturated fatty acids. It is
liquid at room temperature and will solidify at
around –5 °F.
• What about vegetable shortening?????
The chain length has an effect on how liquid a
fat/oil is at room temperature
• Long chain FA
> 12 Carbons
• Medium chain FA
6 - 10 Carbons
• Short chain FA
< 6 Carbons
Hydrogenation of Fatty Acids
• Process used to solidify an oil
• Addition of H to C=C double bonds
• Formation of trans fatty acid
Health Dangers of Excessive Trans Fatty Acid
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Raises LDL
Lowers HDL
Increases risk for heart disease
Current intake is~3% of total kcals
Soon to be on food labels
Minimize Intake of Trans Fatty Acid
• Limit use of hydrogenated fats
– partially hydrogenated vegetable oil
• Limit deep-fried foods
• Limit high fat baked goods
• Limit use of non-dairy creamers
Essential Fatty Acids
Body can only make double bonds after
the 9th carbon from the omega end
Needed for immune function, vision, cell
membrane, and production of
hormone-like compounds
Essential Fatty Acid;
Omega-3 (alpha-linolenic acid)
H H H H H H H H H H H H H H H HH O
H-C--C--C=C--C--C =C--C--C=C--C--C--C--C--C--C--C--C-OH
H H
H
H
H H H H H H H
omega end
alpha
end
1st double bond is located on the 3rd carbon from
the omega end
Omega-3 Fatty Acids
Primarily from fish oil
Also found in canola or soybean oil
Eicosapentaenoic acid (EPA) and
docosahexaenoic acid (DHA) are related
Metabolized to form eicosanoids
Recommend intake of ~2 servings of fish per
week
Omega 3 (Alpha-linolenic acid, C18:3)
2C
2H
Eicosapentaenoic acid (EPA, C20:5)
2C
2H
Docosahexaenoic acid (DHA, C22:6)
Eicosanoids
Essential Fatty Acid
Omega-6 (alpha-linoleic acid)
H H H H H
H
H H H H H H H O
H-C--C--C--C-- C--C =C--C--C=C--C--C--C--C--C--C--C--C-OH
H H H H H H H H H H H H H H H H H
omega end
alpha
end
1st double bond is located on the 6th carbon from
the omega end
Omega-6 Fatty Acid
• Found in vegetable oils
• Only need ~ 1 tablespoon a day
• Arachidonic acid can be made from omega6
• Metabolized to form eicosanoids
Omega 6 (linoleic acid, C18:2)
2C
2H
Dihomo-gamma-linolenic acid (C20:3)
2H
Arachidonic acid (C20:4)
Eicosanoids
Eicosanoids
Eicosanoids are a group of hormone-like
compounds
Regulators of blood pressure, childbirth,
clotting, immune responses, inflammatory
responses, & stomach secretions
By-pass the blood stream and work in the area
of origin
Eicosanoids Have Different Effects
Omega-6 eicosanoids; Archidonic acid
increase blood cot
increase inflammatory responses
Omega-3 eicosanoids, DHA, EPA
decrease blood clotting
reduces heart attack
excess may cause hemorrhagic stroke???
Eicosanoid has different effect on
different tissues
Signs and Symptoms of Essential Fatty Acids
Deficiency
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Flaky, itchy skin
Diarrhea
Infections
Retarded growth and wound healing
Anemia