Lipids (Fats and Oils)
• Non-polar long chains of carbon atoms
• Fatty Acids have carboxylic acid functional
group and methyl group at other end - most
often even number of C atoms
• Saturated fats - contain only single covalent
bonds, no double bonds
• Unsaturated fats - contain one or more double
covalent bonds
Basic Categories of Lipids
1. Fatty Acids fatty acids and glycerol
2. Triglycerides (Glycerol + 3 FA’s) …
mono-, di-, tri1. Phospholipids (Glycerol + 2 FA’s + P
group) amphiphilic (polar and non-polar)
2. Steroids (Derivatives of Cholesterol)
complex and important!
Functions of Lipids in Body
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•
•
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Energy Storage
Energy Source
Insulation/Protection
Cell Membrane Structure
Transport of Fat Soluble Vitamins
Hormones and Signal Molecules
Vitamin D, Bile, Sex Hormones, Prostaglandins
Regulators of Appetite and Satiety
Lots of Lipids to Choose from
in Your Diet
Fatty Acids – are one of the fundamental
building blocks of nutritional lipids!
General Formula of Fatty Acids:
CH3(CH2)n COOH
n = any even #
from 2 to 24
Carbon chain
contains no double
bonds
Carbon chain
contains one or
more double bonds
Classification of Fatty Acids
Fatty Acids:
A chain of C and H atoms with a carboxyl group
At alpha end and a methyl group at omega end.
FAs attached to OH groups, gives off H2O
Bonds between FA and glycerol = ester bond
Attach a FA to glycerol = esterification
Remove FA from glycerol = deesterification
20 different Fatty Acids, vary by:
 Degree of Saturation 
 Length of the C chain
 Shape
Fatty Acids classified by number of C atoms as:
• Short-chain fatty acids (SCFAs): Less than 8 C’s
• Medium-chain fatty acids (MCFAs): 8 to 14 C’s
• Long-chain fatty acids (LCFAs): 16 or more C’s
• Very-long-chain fatty acids (VLCFAs): More than 22 C’s
Saturation and Length of the C chain
Saturated Fatty Acids
Monounsaturated Fatty Acid (MUFA)
Has one double bond
Polyunsaturated Fatty Acid (PUFA)
Has two or more double bonds
Saturated Fatty Acids in Diet
Lauric acid - CH3 (CH2)10 COOH coconut oil,
breast milk.
Myristic acid CH3 (CH2)12 COOH - coconut, palm
kernel oil, butter, cheese, whale blubber.
Palmitic acid CH3 (CH2)14 COOH - poultry, beef,
game meats.
Stearic acid CH3 (CH2)16 COOH - cocoa butter,
beef tallow, lard, butter, beef, pork, lamb.
Stability of Fatty Acids
Rancidity: Spoiling of fats through oxidation
• Double bonds less
stable than single bonds.
• Foods with unsaturated
fats become rancid faster
than saturated fats.
• Need to Add antioxidants
• Limit Oxygen, Heat, Light
• Hydrogenation of Oils
Saturated Fats and Trans Fats are not the same
List the important feature of these Fatty Acids
Essential Fatty Acids (EFA) - unsaturated,
essential to human health, cannot be manufactured
in the body. 1, 2 or 3 EFAs:
1. Linoleic Acid* - only from diet!
2. α-Linolenic Acid
3. Arachnoidic Acid - from linoleic acid!
*When linoleic acid is obtained in the diet, it can be
converted to both arachnoidic and linolenic acid.
Omega-3 Fats
Plant Based: Alpha-Linolenic Acid (ALA) is essential: chia (64%),
kiwi fruit (62%), flaxseed oil (53%), Hemp (20%) walnuts (9%), and
canola oil (10%), soybean oil (7%). Plus, red meat; dairy products.
Animal Based: Eicosapentaenoic Acid (EPA) and Docosahexaenoic
Acids (DHA) fish, shellfish and krill. DHA needed for brain and retina;
EPA its precursor. You can make some EPA and DHA from short-chain
ALA, but does so inefficiently.
Omega-6 Fats
Linoleic Acid (LA) is essential, which is the most prevalent PUFA in
the Western diet, is abundant meat, poultry, eggs, hemp and nutbased oils – Plus corn, sunflower, soybean and canola oil. All to be
avoided!
Arachidonic Acid (AA), important (membranes, regulate inflammation,
promote blood clotting, communication). Made by EFA’s
Essential Fatty Acids Manufacture
Eicosanoids and Cell Membranes
• Linoleic Acid
– Converted to Arachidonic Acid
cell membranes in
nerve tissue and retina.
• Alpha-Linolenic Acid (ALA)
– Converted to Eicosapentanoic acid (EPA)
– Elongated to Docosahexanoic acid (DHA)
• EPA and Arachidonic Acid (AA) make Eicosanoids.
Hormone-like substances regulating blood clotting,
immune system, inflammation, blood pressure
Eicosanoids
• Prostaglandin- hormone-like compounds. Various
actions include: uterine contraction, sleep cycles,
body temp regulation, vasoactive effects.
• Prostacyclin- made by blood vessel walls, potent
anticoagulent (thins the blood).
• Thromboxane- stimulant of blood clotting.
• Leukotrine- chemical signal regarding state of
inflammation. Involved with hypersensitivity
reactions, and asthma (contracts bronchioles).
• Lipoxin- made by WBCs, involved in immune and
allergic responses.
Dietary Deficiency of Fatty Acids
Not enough FAs in diet causes:
– Flaky skin
– Depression; lower alertness
– Compromised immune system
– Infections
– Slowed wound healing
– Anemia
– Diarrhea
Triglycerides
1
2
3
Esterification Process
Note the different
configuration of the ‘tails’
Formation of Triglycerides
The Functions of Triglycerides in the Body
1 – Energy Storage and Energy Source
Lipids are energy rich (9kcal/g vs 4kcal/g). The process to use lipids
as a fuel source is complex and secondary to glucose in most diets.
Fats as Fuel
Preferred by the heart, liver, and resting muscle
Spares glucose for use by nervous system and RBCs
Provides a backup source of energy between meals
Glucose is needed to metabolize fat.
Glycerol portion of fat can make small amounts of glucose
The Functions of Triglycerides in the Body
2 – Insulation and Protection
Triglycerides are stored in adipose tissue inside adipocytes (fat cells).
Subcutaneous fat is the adipose under the skin, it insulates your Tb
Visceral fat surrounds internal organs, protects and cushions.
3 – Nutrition
The fat-soluble vitamins, A, D, E, and K all require lipids in the body
to absorb them. Vitamins E, D, and K are also stored in the fat tissue.
Note: The fatty acids in a
triglyceride molecule are
usually comprised of all
saturated or unsaturated.
Phospholipids
Like a Triglyceride – with 1 FA replaced with alcohol/sugar phosphate group
both Hydrophobic
and Hydrophilic
Phospholipid Structure
Phospholipid Bilayer
of all Cell Membranes
Average Cell membrane contains 50% lipids
75% Phospholipids; 20% Cholesterol; 5% Glycolipids
Lecithin
aka phosphatidylcholine –
is a type of phospholipid.
• Synthesized by the liver
• Functions
• Used as an emulsifier in
foods (e.g., salad dressing)
• A major phospholipid in the
cell membrane
micelle
Sterols!
Sterols contain the steroid of four fused carbon rings.
The Liver Uses Cholesterol as starting Material for
Vitamin D3
Sex Hormones (Estrogen and Testosterone)
Bile Acid
Highest content in
liver, brain, heart, and kidney
Cortisol
Structural elements of cells
Time Magazine Cover from 1984 blaming
cholesterol and saturated fats as a cause of
heart disease.
Time Magazine cover story in 2014.
Scientists were wrong about saturated
fats. They don’t cause heart disease
after all.
All Fats are Not Equal!
Omega-3- and 6-Fatty Acids

Cholesterol (LDL’s and HDL’s)

Hydrogenated Vegetable Oils
Trans Fats and Acrylamide
Just

Say

No!
*Dr. Ancel Keys (1958)
Ischemic Heart Disease
Cholesterol
Vitamin D
Cortisone
Glucocorticoids
Mineralcorticoids
Steroid Hormones
(testosterone, estrogen,
progesterone)
Bile Salts
Acetyl CoA
Hydroxymethyl Glutaric Acid (HMG-CoA)
Statin = HMG-CoA reductase inhibitors
Mevolaonate
Mevolaonate Pyrophosphate
Isopentenyl Pyrophosphate
Geranyl Pyrophosphate
Famesyl Pyrophosphate
*Without these 3
end products you
age prematurely
Squalene
*Ubiquinone
(CoQ10)
*Cholesterol
*Dolichol
Biochem Cell Biol. 1992 Jun;70(6):422-8
Dolichol in Brain
Decreased Levels of Dolichol result in:
• decrease in energy
• compromised immune system
• hormone imbalance or deficiency
• low sperm count
• cell damage or cell death
• poor brain function
• nervous disorders
• depression
Ubiquinone (CoQ10)
The heart, liver and
kidney have highest
CoQ10 concentrations
CoQ10 is Protectant!
Unsaturated Oils vs. Saturated Fats
Polyunsaturated Fats – e.g., canola, soybean,
safflower, corn - easily become rancid when
exposed to oxygen and produce free radicals in
the body.  Just Say No!
*Olive oil – Still good; best if not heated!
Why is it that every processed food has the
same basic 5 ingredients in them?
The Farm Bill

SayYes
Please!
Virgin Coconut Oil - a saturated fat with medium
chain Fatty Acids (MCFA) - extremely heat stable and
very beneficial for human physiology. Saint-Onge and Jones (2003)
* Coconut Oil does not elevate cholesterol or cause heart disease.
* Reduces weight gain.
* 50% Lauric Acid – same lipid in breast milk. Protective properties.
Eating fat makes you fat and increases your
risk of cardiovascular disease - Right?
One of the best foods to eat to control blood glucose
is Fats - the right fats! Yes - like Coconut Oil!
Triglyceride Digestion Begins in Mouth
and Stomach
• The digestion of fat begins in the mouth with chewing.
– Food mixes with saliva and lingual lipase.
– Lingual lipase hydrolyzes the medium-chain fatty
acids.
• The bolus of food travels through the esophagus into
the stomach.
– Gastrin is released from the gastric pits lining the
stomach and stimulates the release of gastric juices,
rich in gastric lipase.
– Gastric lipase hydrolyzes one fatty acid from the
triglyceride, which produces a free fatty acid and a
diglyceride.
Most Triglycerides Digested and
Components Absorbed in the Small Intestine
• Fat globules in chyme tend to cluster together.
• In the intestine, bile emulsifies larger fat droplets into
smaller fat droplets.
• Allows pancreatic lipase to digest the lipids easily.
The resulting lipid complex is a micelle – these transport
the lipid complex across the small intestinal wall.
• Cholecystokinin (CCK) is the hormone that stimulates the
gallbladder to release bile.
• CCK triggered to release when cells of the duodenum
detect the presence of lipids.
Phospholipids
– Emulsified by bile during digestion
– Dismantled into 2 free FA’s phospholipid remnant
– Packaged as micelles & transported through
intestinal wall
Sterols
– Not digested
– Carried and absorbed intact by micelles
– Bile emulsifies sterols.
Undigested/non absorbed lipids:
– Bind with fiber
– Are eliminated in the feces
Absorption of Dietary Lipids
Chylomicrons Facilitate Lipid Absorption
Glycerol and short- to medium-chain fatty acids are
absorbed directly into the bloodstream.
Long-chain fatty acids combine with phospholipids and
cholesterol to form Chylomicrons.
Chylomicrons Facilitate Lipid Absorption
Chylomicrons are too large to be absorbed directly into
the bloodstream.
– Travel through lymphatic system first
– Exit the lymph and enter bloodstream via thoracic
duct next to the heart
– Lipoprotein lipase (LPL) hydrolyzes triglycerides in
the chylomicrons as they travel to liver via the
bloodstream.
Fat Absorption
• Bile and lecithin emulsify and break down fats into
triglycerides
• Lipases in small intestine break down triglycerides in
food into FAs and monoglycerides
• Monoglycerides and FAs absorbed through villi into
intestinal cells
• The reassembled into triglycerides
• Triglycerides collect and combine with protein,
cholesterol, and phospholipids to form chylomicrons
Nutrients ultimately
end up in your Blood
Blood has 2 parts:
Plasma (fluid)
and Cells!
Plasma is 92% Water and we know that Lipids are
hydrophobic, so they require special mechanism
for transport through the blood to the tissues.
Lipoproteins
Lipoproteins
Lipid Transport Structures
1. Chylomicrons - largest and least dense transport diet
derived triglycerides from small intestine, through the
lymphatic vessels, into blood to body cells which remove
lipids from them.
The liver cells remove the remnants of the chylomicrons
from the blood and reassembles them into new
triglycerides.
Liver - site of lipid synthesis;
uses fatty acids to make cholesterol,
other fatty acids, triglycerides from
carbs, protein and alcohol.
New lipids combine with a protein carrier
and transported around the body
2. Very Low Density Lipoproteins (VLDL) made liver
and about 50% triglyceride transport (some
cholesterol, and phospholipid).
The VLDL travel through the body and cells remove
triglyceride from them. As they lose triglyceride, the
proportion of cholesterol increases and they become
more dense; they become a low-density lipoprotein
(LDL).
3. Low Density Lipoprotein (LDL) mostly cholesterol
(about 50%). They circulate through body and release
triglyceride, cholesterol and phospholipid to body cells.
Body cells require the lipids to make cell membranes,
hormones or store them for later use.
The liver removes LDL from circulation.
LDL’s is not cholesterol and they are not
good or bad. It is a
Carrier of Cholesterol
and other lipids.
4. High Density Lipoprotein (HDL) transports
cholesterol from the cells back to the liver for recycling
or disposal.
This is where the role of HDL in picking up ‘excess
cholesterol’ has become the focus of its role and the
declaration of it as the “good cholesterol”.
Please realize that HDL is not cholesterol; it is a Carrier
of Cholesterol.
Chilomicrons deliver almost all fats from intestine to liver
Very Low Density Lipoproteins (VLDL) triglycerides from liver to tissue cells
Low Density Lipoproteins (LDL) delivers cholesterol to tissues cells
High Density Lipoproteins (HDL) returns excess cholesterol from cells to liver
Lipids in the Diet
• Fats provide flavor
• Contribute to satiety
• Are essential for completion of development
of central nervous system
• Act as emulsifiers (thickeners for foods and
suspend fats)
Is there a difference between Various
Fats? Are there Good Fats and Bad Fats?
• Currently no RDA for fat- because they are idiots!
• Upper limit of 10% energy intake from
polyunsaturated FAs is recommended
– Americans consume about 7%
• No more than 30% of calories from fat in most food
pyramid diets
– Most Americans gets about 33-35%
• AHA recommends 20-30% from fats, and less than
10% from saturated fats
• Limit cholesterol to 300 mg per day
– Typical American diet is 200-400 mg
Rotten Fat Intake – that is, trans fats
• Rancid fats contain peroxides and aldehydes that damage cells
– Polyunsat fats go rancid easily because double bonds are
damaged easily by oxygen, heat, metals, and light- then
they decompose
– Sat trans fats are resistant to this
– Highest risk in fish and vegetable oils, packaged fried foods
– Prevent rancidity by breaking double bonds and adding
hydrogen (hydrogenation), using airtight packaging, or
adding antoxidants (vitamin E, vitamin C)
• Hydrogenated fat excess (trans fats) raises blood cholesterol
levels, lower HDL, increase inflammatory responses, raise
body weight stored in abdomen in visceral fat (increases type
2 diabetes risk)
Fat Replacements - A Really Bad Idea.
Why would you want to take something that
your body cannot function properly without and
substitute it with something you do not need
and may actually be bad for you?
Engineered Fats- synthesized in lab
– Olestra- made by linking FAs to sucrose
• Cannot be digested by human or bacteria- yields no energy
– Olestra can be used in cooking and frying
– Olestra absorbs vitamins A, D, E, K- so manufacturers add
these vitamins to products with olestra
– Can also cause abdominal cramping and loose bowels with
more than 20g at a time
– Also binds carotenoids, which are useful for function of
eye, and reduces chances of heart disease and cancer