Post on 25-May-2015
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The Lipids: Triglycerides,
Phospholipids, and Sterols
carbohydrates, fatty acids and
triglycerides are composed of
carbon (C), hydrogen (H), and
oxygen (O).
Because these lipids have
many more carbons and
hydrogens in proportion to
their oxygens, however, they
can supply more energy per
gram than carbohydrates
Triglyceride contains one
molecule of glycerol and
three fatty acids
Fatty acids may be saturated
or unsaturated
Fatty acids may be 4 to 24
(even numbers of) carbons
long, the 18-carbon ones
being the most common in
foods
The 18-carbon fatty acids that
fit this description are linolenic
acid (omega-3) and linoleic
acid (omega-6).
Stearic acid, an 18-carbon saturated fatty acid
Stearic acid
Oleic acid, an 18-carbon monounsaturated fatty acid
Linoleic acid, an 18-carbon polyunsaturated fatty acid
Condensation of Glycerol and Fatty Acids to
Form a Triglyceride
Comparison of Dietary Fats
Most fats are a mixture of saturated,
monounsaturated, and polyunsaturated fatty
acids.
phospholipid is lecithin
cell membrane is made of phospholipids
A Bile Acid
bile acids the liver makes from cholesterol. It
is then bound to an amino acid to improve its
ability to form micelles, spherical complexes
of emulsified fat. Most bile acids occur as bile
salts, usually in association with sodium, but
sometimes with potassium or calcium
Emulsification of Fat by Bile
Digestion (Hydrolysis) of a Triglyceride
Chylomicrons
VLDL (Very-Low-Density Lipoproteins)
LDL (Low-Density Lipoproteins)
HDL (High-Density Lipoproteins)
Absorption of Fat The end products of fat digestion
are mostly monoglycerides, some
fatty acids, and very little glycerol.
Their absorption differs depending
on their size. (In reality, molecules
of fatty acid are too small to see
without a powerful microscope
Sizes and Compositions of the Lipoproteins
Cholesterol in Selected Foods
Sources of Omega-3 and Omega-6 Fatty Acids
The USDA Food Guide amounts of fats that
can be included as discretionary kcalories
when most food choices are nutrient dense
and fat 30% total kcal:
• 11 g for 1600 kcal diet
• 15 g for 1800 kcal diet
• 18 g for 2000 kcal diet
• 19 g for 2200 kcal diet
• 22 g for 2400 kcal diet
For perspective, 1 tsp oil = 5 g fat and
provides about 45 kcal