Table of Contents
- Lipids are molecules that cannot dissolve in water.
- Cells synthesize most lipids including phospholipids, sterols, and fats.
Structure of lipids
- All lipid molecules are hydrophobic.
- Lipids are hydrophobic because they have several nonpolar covalent bonds.
- Unlike other macromolecules, lipids are not polymers.
- According to their structures, lipids are divided into many subcategories;
- Fats and oils have a similar structure.
- They contain fatty acids that joined the backbone of glycerol.
- Phospholipids contain unique head groups.
- Waxes are esters of a carboxylic acid with R groups contain long straight hydrocarbons.
- Sterols have four fused rings. They are useful in the production of hormones.
- Fats and oils have a similar structure.
Saturated fatty acids
- Fatty acids are long chains of carbon and hydrogen.
- These are components of lipids.
- They can be unsaturated or saturated.
- Saturated fats involve carbon atoms joined together with single bonds in fatty acids. The carbon atoms form four bonds and each contains two hydrogen bonds.
- Unsaturated fats contain carbon atoms with double bonds. The atoms with the double bond can only join one hydrogen atom.
Forming fats and oils
- Fats and oils are formed by attachment of three fatty acids to a glycerol backbone.
- They are referred to as triglycerides because of the three fatty acids.
- Glycerol is formed from three-carbon alcohol with a hydroxyl group attached to each carbon atom.
- Fats are solids at room temperature.
- Oils are in liquid form at room temperature.
- Animal fats like those in meat and dairy products are saturated.
- Fish and plant oils are unsaturated like those found in nuts.
Other types of lipids
- Oils and fats are the most useful lipids.
- Phospholipids and triglycerides have a very similar structure.
- Phospholipids are formed by the condensation reaction between fatty acids and glycerol.
- The phosphate negative charges make phospholipid head groups hydrophilic.
- Amphipathic lipids are those with both nonpolar and polar ends.
- Waxes are generated from long-chain alcohols and fatty acids.
- They are long-chain hydrocarbons with several nonpolar hydrogen carbon bonds.
- Sterols are processed from four associated carbon rings. The rings contain several carbon-hydrogen nonpolar bonds.
- Sterols include steroid hormones, cholesterol, and vitamin D.
Roles of lipids
- Fat insulation is important in animals.
- Fat provides a shock-absorbing layer in animal organs.
- They are important in plasma membrane structure.
- The plasma membrane is made up of numerous phospholipids.
- The cell membrane contains a bilayer of phospholipids with hydrophilic heads outside the membrane while hydrophobic heads facing inwards.
- Lipids are waterproof.
- Plants use axes to prevent leaf damage.
- Waterbirds use waxes to keep their feathers dry.
- Lipids are useful in signaling.
- Various steroid hormones like estrogen and testosterone enhance useful human developmental changes.
- These lipids have a sugar residue.
- They do not have phosphate groups.
- The sugar residue can be polysaccharide, disaccharide or oligosaccharide.
- Glyceroglycolipids are formed from the attachment of sugar and fatty acid residues to a glycerol backbone.
- Sphingoglycolipids are formed by attachment of fatty acids and sugar residues to a sphingosine backbone.
- Lipoproteins are classified into two classes according to their density.
- Low-density lipoproteins are useful in the transportation of phospholipids and cholesterol from the liver into the cells.
- High-density lipoproteins;
- They are used to transport cholesterol and phospholipids back into the liver from the cells.
- High LDL and low HDL levels can be used to indicate looming atherosclerosis.
- Eicosanoids are signaling molecules with twenty carbon atoms.
- They are derived from polyunsaturated fatty acids like eicosapentaenoic acids or arachidonic acid.
- The above polyunsaturated fatty acids undergo reactions that change them into different eicosanoids classes.
- The classes include: prostaglandins, thromboxane, prostacyclin and leukotriene
Trans fat facts
-mandatory to list trans fat on label 2006
-20% of trans fat is natural (milk/meat)
-80% of trans fat in the diet is from processed food
-.5 trans fat on the label- could read trans fat free
major sources of trans fat in the diet
cakes cookies crackers pies bread 40%
-animal products 21%
-fried potatoes 8%
-potato chips, corn chips, popcorn 5%
-household shortening 4%
- other 5% include breakfast cereal, and candy
Safe levels of trans?
no more than 1% of total calories
-no safe level identified
- CDC avoiding artificial trans fat completely could prevent up to 20,000 heart attacks and 7,000 coronary disease deaths in the US every year !
Phospholipids and Sterols make up _% of the lipids in diet
Lecithin is different than a triglyceride because it only has _ fatty acids attached to a glycerol & the 3rd position is a __ group and a molecule of _
2, phosphate, choline
benefits of phospholipids:
emulsifier; substance with both water soluble and fat soluble portions that promote the mixing of oils and fats in watery solutions because one end is hydrophobic and the other is hydrophilic
ex; egg liver soybeans wheat germ and peanuts
Roles of phospholipids in the body
-Cell membranes (lecithin)
-allow fat soluble VITAMINS and HORMONES to pass in and out of cells easily
-emulsifiers in body helping to keep fats suspended in blood and body fluids
-supplemenatation not required
Sterols- Cholesterol (last FA)
Sterols found in animal products. Only sterols found in animals have significant cholesterol
aka phytosterols are structurally similar to cholesterol.
-interfere with cholesterol absorption.
Do not contain significant cholesterol, and inhibit cholesterol absorption
A diet high in plant sterols lowers _ __ levels
Lowering your cholesterol with TLC:
-low saturated fat
-10-20g soluble fiber
-2g plant sterols and stanols
Cholesterol is the starting material for these compounds:
-adrenal hormones(cortisol, cortisone and aldosterone)
The cholesterol manufactured inside the body is known as …
The cholesterol that one consumes outside the body
fat in small intestine triggers release of hormone CCK which signals the gallbladder to release bile
Bile acids act as a __
Bile is either or with fiber reducing body cholesterol
In the liver bile is made from _.
in the gallbladder, bile is __ .
in the small intestine, bile emulsifies __ .
Lipoprotein; that contains triglycerides, phospholipids, cholesterol and protein. Transport dietary lipids from intestines to other parts of the body
Ship cholesterol and fatty acids made in the liver to other parts of the body
-as body removes triglycerides the VDL shrink and become LDL.
Low density lipoproteins.
-carry triglycerides, cholesterol and phospholipids to body cells to build new tissues
carry cholesterol from cells back to the liver for recycling or disposal, lipoprotein
Removes cholesterol in the cells and carries it back to the liver for disposing.
Essentially clears cholesterol
hormone that fat cells secrete
an adipokine that protects against inflammation diabetes heart disease. Obesity decreases the release of Adiponectin
Essential fatty acids
Polyunsaturated fatty acids:
omega 6-Linoleic + Arachidonic acid
omega 3-Linolenic -DHA+ EPA
EPA + DHA
Fish oils (omega 3)
derivatives of EPA and DHA and arachidonic acid.
-Hormone-like biologically active compounds that HELP REGULATE BLOOD PRESSURE AND CLOTTING
Omega 3 Eicosanoids
lower blood pressure prevent clot formation protect against irregular heart beat reduce inflammation
omega 6 eicosanoids
promote clot formation, promote inflammation, promote blood vessel constriction
EPA + DHA consumption :
less than 2 weeks, each 1g/day increase lead to 5.9% reducing triglycerides
(Linolenic acid )
Omega 3 from Fish
AHA: +2 servings (3.5oz) per week
-excellent source of protein
-to decrease mercury avoid Big Fish: shark,swordfish,kingmackerel,tilefish
-Canned tuna- 6oz or 12oz light per week
-Farm raised fish are lower in both mercury but also lowered in Omega 3
Omega 3 sources
Fish- Salmon, Mackerel, Bluefish, Herring, Anchovy
Other- Flaxseed Oil, Canola (rapeseed), Walnuts, Butternuts, Soybean Oil, Mustard Oil, Pecans
Plant Based n3 PUFA
chia, flax, hemp, rapeseed..small amounts converted to EPA
-cannot be total replacement for marine PUFA
-satiety (the feeling of being full)
-carry fat soluble vitamins
-supply essential fatty acids
-contribute aroma and flavor
Food Cholesterol _ _ raise blood cholesterol as much as saturated fat does
acts like saturated fat in the body and raises blood choelsterol
Monounsaturated and Polyunsaturated fatty acids
increasing these- most effective strategy against heart disease and decreasing the amount of saturated fat that you’re eating
1% decrease in dietary saturated FA=
2% decrease in LDL and 2% decrease in heart disease risk
Hardening of the arteries begins w/ the …
accumulation of fatty streaks along the inner arterial walls
Arteries gradually enlarge and harden as they fill up with:
Cells Lining blood vessel may be damaged due to:
-Hypertension(high blood pressure)
-Toxins from Cigs
-elevated Homocysteine (amino acid)
-some viral and bacterial infection
immune system send in _ and the __ cells of the artery wall try to repair the damage
macrophages, smooth muscle
C- Reactive Pro
used as a marker to predict future heart attacks
-the higher the blood levels of CPR the greater risk
When atherosclerosis restricts blood flow, it deprives the heart w/ oxygen:
Agnia-pain and pressure around the heart
Heart attack; blood flow cut off from the heart, heart muscle dies
TIA aka stroke- restricted blood flow to the brain
Obesity and obesity risk factors
the double bond is a …
point of unsaturation
a fatty acid with two hydrogens missing and 1 double bond is known as a
monounsaturated fatty acid
monounsaturated, abundant in olive oil and canola oil
a fatty acid that has two or more carbon to carbon double bonds is known as
18 carbons w/ 2 double bonds
Linolenic acid has
18 carbons + 3 double bonds
cis vs. trans
cis -the hydrogens next to the double bonds are on the same side of the carbon
trans- hydrogen next to the double bonds are on the opposite sides of the carbon chain
phospholipids are used as …
the goal of fat digestion is to dismantle triglycerides and turn them in to ….
monoglycerides, fatty acids, and glycerol
enzyme in the mouth that starts fat digestion
Digestion of fat in the stomach
-disperses fat into tiny droplets
-help expose fat for attack by gastric lipase
-gastric lipase works best in acidic environment of stomach
the major fat digesting enzymes are :
pancreatic lipase, and some intestinal lipases
The enzymes literally remove each of a triglycerides _ __ one at a time.
a triglyceride with its fatty acids removed is known as a
monoglyceride. unless it has all 3 of the fatty acids removed then its just a molecule of glycerol
tiny spherical complexes of emulsified fat that arise during digestion. most contain bile salts and the products of lipid digestion, including fatty acids, monoglycerides and cholesterol
the _ diffuse in to the intestinal cells, where the monoglycerides and long chain fatty acids are reassembled into new _
micelles , triglycerides
newly made triglycerides and and other lipids (cholesterol & phospholipids) are pack with protein into transport vehicles known as ….
solve the bodys challenge of transporting fat thru the watery blood stream
LDL- low density lipoproteins
LDL cirulates thru the body making their contents available to the cells of all tissues- muscles (heart) fat stores, mammary glands, etc. The cells make triglycerides, cholesterol. and phospholipids to use for energy.
HDL- high density lipoproteins
the liver makes HDL to remove cholesterol from the cells and carry it back to the liver for recycling or disposal.
-lowers risk of heart disease
LDL and HDL reflect the and __ of lipids and proteins within them- not the type of cholesterol.
proportions and types
the fat cells of adipose tissue ..
take up and store triglycerides
adipose tissues secretes a hormone called __
adipokines- proteins that help regulate energy balance and influence several body functions
DRI fat %
DRI saturated fat =
less than 10%
less than 300 mg a day
the two essential fatty acids are :
linoleic acid (18 carbon omega 6 fatty acid)
linolenic acid (18 carbon omega 3 fatty acid)
what protein is produced by adipose cells that promotes inflammation and causes insulin resistance
Omega 3, present in fatty fish and linolenic acid
Omega 3 PUFA, in fatty fish, linolenic acid
Omega 6 polyunsaturated, linoleic acid,present in meat and other animal products.
both omega 3 and omega 6. they are “hormone like”
causes constriction and relaxation of blood vessels and muscles
What is the main cause of CVD (heart disease)
what is the nations number one killer of adults
heart disease (CVD)
What does high LDL lead to?
LPL (liporotien lipase)
Hydrolyzes triglycerides and directs them into the cells
Hormone sensitive lipase
Responds to the body’s need for fuel
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