Transcript THE LIPIDS: TRIGLYCERIDES, PHOSPHOLIPIDS, & STEROLS

THE LIPIDS:
TRIGLYCERIDES,
PHOSPHOLIPIDS, &
STEROLS
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Lipids
A family of compounds that includes
triglycerides (fats and oils), phospholipids,
and sterols.
Fats- lipids in foods or the body, both of
which are composed mostly of
triglycerides.
Oils- liquid fats at room temperature.
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Triglycerides
The chief form of fat in the diet and the
major storage form of fat in the body
Composed of a glycerol backbone with
three fatty acids attached
The most common triglyceride is the 18
carbon stearic acid.
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Fatty Acids
 Fatty acid- an organic compound composed of a
carbon chain with hydrogens attached and an
acid alcohol group (COOH) at one end.
 Saturated FA- a fatty acid carrying the maximum
number of hydrogen atoms.
 Unsaturated FA- a fatty acid that lacks hydrogen
atoms and has at least one double bond
between carbons.
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MUFAs And PUFAs
Monounsaturated FA- a fatty acid that
lacks two hydrogen atoms and has one
double bond between carbons.
Polyusaturated FA- a fatty acid that lacks
four or more hydrogen atoms and has two
or more double bonds between carbons.
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Health Effects Of PUFAs And
MUFAs
 PUFAs lower LDL or “bad” cholesterol..
 Some research suggests that MUFAs increase
HDL or “good” cholesterol while other research
suggests that PUFAs and MUFAs lower both
LDL and HDL cholesterol.
 PUFAs should replace saturated fats in the diet.
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Food Sources Of PUFAs &
MUFAs
PUFAs
Safflower oil
Sunflower oil
Corn oil
Soybean oil
Cottonseed oil
MUFAs
Olive oil
Canola oil
Peanut oil
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Essential Fatty Acids
A fatty acid needed by the body but not
made in amounts sufficient to meet
physiological needs. The human body
makes all its fatty acids with the exception
of linoleic and linolenic acid.
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Omega 3 & 6 Fatty Acids
 Omega- the last letter of the Greek alphabet, used
by chemist to refer to the position of the first
double bond from the methyl end.
 Linoleic acid- primary member of the omega-6
family in which the first double bond is six carbons
from the methyl end of the carbon chain.
 Linolenic acid- primary member of the omega-3
family in which the first double bond is 3 carbons
away from the methyl end.
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Health Effects Of Essential
Fatty Acids
May play an important role in the
prevention and treatment of heart disease,
hypertension, arthritis, and cancer.
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Food Sources Of Essential
Fatty Acids
Omega-6
 Leafy vegetables
 Seeds
 Nuts
 Grains
 Meats
 Vegetable oils
Omega-3
 Nuts
 Seeds
 Wheat germ
 Shellfish
 Fish
 Vegetable oils
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Hydrogenation And TransFatty Acids
 Hydrogenation- a chemical process by which
hydrogens are added to unsaturated fats to
reduce the number of double bonds, making the
fat more saturated and resistant to oxidation.
 Trans-fatty acids- fatty acids with an unusual
configuration around the double bond. They
occur as a result from the process of
hydrogenation.
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Health Effects Of Trans-Fatty
Acids
Trans-fatty acids alter blood cholesterol
the same way saturated fats do.
There is a link between trans-fatty acids
and heart disease.
Margarine versus butter?
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Phospholipids
 A compound similar to a triglyceride but having a
phosphate group (phosphorus containing salt)
and choline (nitrogen-containing group) in place
of one of the fatty acids
 Found in foods such as eggs, liver, soybeans,
wheat germ, and peanuts
 Important constituents of cell membranes
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Sterols
Compounds composed of carbon,
hydrogen, and oxygen molecules arranged
in rings, with any variety of side chains
attached.
The most famous sterol is cholesterol.
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Role Of Sterols
Sterols serve as important compounds in the
body. Sterols include:
Bile acids
Sex hormones
Adrenal hormones
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Cholesterol
 Cholesterol is made endogenously (in the
body).
 Exogenous cholesterol from our diet is
consumed only from animal sources such as
meat, eggs, fish, poultry and dairy products.
 Endo = within
 Exo = outside (the body)
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Digestion Of Lipids
Fats are hydrophobic or water-fearing.
In the mouth- the salivary glands release lipase
which plays a small role in the start of digestion.
In the stomach- fat floats as a layer above the
other components of food, as a result little
digestion takes place here.
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Digestion Of Lipids {continued}
 In the small intestines- when fat arrives in the
duodenum, the gall bladder receives a signal to
release bile from storage.
 The hormone cholecystokinin (CCK) is what triggers
the gallbladder to release bile.
 Bile emulsifies the fat.
 Pancreatic lipases are released as well as some
intestinal lipases.
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Absorption Of Lipids
 Small molecules of glycerol, medium and short chain
fatty acids diffuse easily into the intestinal cells and
are absorbed directly into the bloodstream.
 Larger molecules, the monoglycerides and long chain
fatty acids form micelles.
 Micelles- tiny spherical complexes that arise during fat
digestion carrying fatty acids and monoglycerides into
the cells.
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Absorption of Lipids {continued}
 Once inside the cells, the fatty acids and
monoglycerides form new triglycerides.
 The new triglycerides, along with cholesterol and
phospho- lipids, form into transport vehicles called
chylomicrons.
 The chylomicrons are released into the lymphatic
system by the intestinal cells.
 The chylomicrons travel through the lymph to the
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blood stream.
Transport Of Lipids
 Lipoproteins- clusters of lipids associated with protein
that serve as transport vehicles for lipids in the lymph
and blood.
 Chylomicrons- the class of lipoproteins that transport
lipids from the intestinal cells into the body.
 VLDL- very low density lipoprotein, the type of
lipoprotein made primarily by the liver to transport
lipids to tissues of the body; Composed mainly of
triglycerides.
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Transport Of Lipids
{continued}
 LDL- low density lipoprotein, the type of lipoprotein
derived from VLDLs as cells remove triglycerides
from them; Mainly composed of cholesterol.
Known as “bad” cholesterol because elevated
levels lead to heart disease.
 HDL- high density lipoprotein, the type of
lipoprotein that transports cholesterol back to the
liver from the cells; Composed mainly of protein.
Known as “good” cholesterol because optimal
levels decrease the risk of heart disease.
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Lipids In The Body
Triglycerides are stored in the adipose
cells.
Unfortunately the body’s storage is
unlimited.
Lipids provide more than twice the
energy of carbohydrates.
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Fats In Foods
 The degree of unsaturation of fats affects health.
 The degree of unsaturation influences firmness at
room temperature.
 Butter is more solid than margarine as it contains
more saturated fat.
 Vegetable oils are liquid at room temperature due
to their large proportions of unsaturated fat.
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Recommended Intakes Of Fat
Total fat should account for 30% or less of
total energy intake daily.
Saturated fat should account for no more
than 10% of total energy intake.
Dietary cholesterol should not exceed 300
milligrams daily.
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Avoid The “Hidden Fats”
Salad dressings
Tuna, egg, potato, pasta salads
Meats marbled with fats
Foods such as olives, avocados, and
nuts
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