Lipids are
Fats
Which lipids are most abundant in both foods and the body
Triglycerides
Why can lipids supply more energy per gram than carbohydrates?
Because lipids have many more carbons and hydrogens in proportion to their oxygens.
Every triglyceride contains how many glycerols and fatty acids?
1 glycerol and 3 fatty acids
What family of compounds are lipids?
Triglycerides, phospholipids, and sterols
Define fats
Lipids that are solid at room temperature
TRUE or FALSE: Lipids are insoluble in water
TRUE
Define oils
Lipids that are liquid at room temperature
Omega-3 and Omega-6 are what type of fatty acid?
Polyunsaturated
How many carbons long can fatty acids be?
4 - 24 (even numbers of) carbons long
What are the most common fatty acids in foods
18-carbon long ones
Name of 18-carbon fatty acids of Omega-3 and Omega-6
Linolenic Acid = Omega-3 ; Linoleic Acid = Omega-6
Benefits of Omega-3 and Omega-6 's
They are part of longer-chain fatty acids that help regulate blood pressure, blood clotting and other body functions.
The following is acetic acid, describe
Two-carbon organic acid with a Methly end (left CH3) and an acid end (right COOH). Acetic acid is the shortest acid.
Compound that gives vinegar its sour taste
Acetic acid
Fatty acid is inorganic or organic?
Organic
Describe a fatty acid chemical make-up/structure.
Chain of carbons and hydrogens; acids groups (COOH) on one and and Methyl group (CH3) on the other end.
The length of a fatty acid carbon chain is?
Even numbers up to 24
What length fatty acid carbon chain is most abundant in our food supply?
18-carbon fatty acids
Simplest of 18-carbon fatty acids
Stearic Acid
Stearic acid is saturated or unsaturated?
Saturated
The following structure represents?
Stearic Acid
Long-chain fatty acids have carbon chains of what length?
12 - 24 carbons
Examples of long-chain fatty acids most common in the diet are
Meats, fish, and vegetable oils
Medium-chain and short-chain fatty acids have carbon chains of what length?
6 - 10 carbons and < 6 carbons respectively
Examples of medium-chain and short-chain fatty acids most common in the diet are
Primarily dairy products
Every carbon MUST have how many bonds?
4
A fatty acid carrying the maximum possible number of hydrogen atoms is called
Saturated fatty acid
An example of a saturated fatty acid is
Stearic acid
A fatty acid that lacks hydrogen atoms and has at least one double bond between carbons is called
Unsaturated fatty acid
The following structure represents _. Why is it considered monounsaturated?
(18-Carbon) It is monounsaturated because it lacks two hydrogen atoms and has one double bond between carbons
Define point of unsaturation
(at the double bond) the double bond of a fatty acid, where hydrogen atoms can easily be added to the structure
Define polyunsaturated fatty acid
(PUFA) A fatty acid that lacks four or more hydrogen atoms and has two or more double bonds between carbons.
An example of a 18-carbon polyunsaturated fatty acid
Linoleic Acid (2 double bonds - Omega-6) [Linolenic acid = 3 double bonds, Omega-3)
Linoleic Acid
An essential fatty acid with 18 carbons and 2 double bonds
Linolenic Acid
An essential fatty acid with 18 carbons and 3 double bonds
Common food source of Stearic acid
Most animal fats
Common food source of Oleic acid
Olive, canola oils
Common food source of Linoleic acid
Sunflower, safflower, corn, and soybean oils
Common food source of Linolenic acid
Soybean and canola oils, flaxseed, walnuts
Define monounsaturated fatty acid
(MUFA) a fatty acid that lacks 2 hydrogen atoms and has one double bond between carbons
An example of a monounsaturated fatty acid
Oleic acid
What does the numbers in Omega-3 and Omega-6 represent?
The numbers indicate the position of the first double bond in a fatty acid counting from the methyl (CH3) end.
What types of fatty acids belong to the omega-9 group
Monounsaturated. Oleic acid (common in olive oil) is an omega-9 fatty acid. Also predominant in monounsaturated fatty acid in the diet
Define triglycerides
The chief form of fat in the diet and major storage form of fat in the body. Composed of a molecule of glycerol and three fatty acids attached; also called triacylglycerols (try-ay-seel-GLISS-er-ols)
Define glycerol
An alcohol composed of a three-carbon chain, which can serve as a backbone for a glycerol
How are triglycerides made
Series of condensation reaction combine hydrogen atom (H) from the glycerol and a hydroxyl (OH) group from a fatty acid forming water (H2O)
REVIEW: Glycerol structure
When glycerol is free an OH group is attached to each carbon. When glycerol is part of a triglyceride each carbon is attached to a fatty acid by a carbon-oxygen bond
Key points on regarding "firmness
#NAME?
Saturated vegetable oils are
Tropical oils" (cocoa butter, palm oil, palm kernel oil, coconut oil)
How are fats effected when exposed to oxygen (oxidation / oxidation reaction)
become spoiled
TRUE or FALSE: Saturation affects stability
TRUE
Define oxidation
process of a substance combining with oxygen; oxidation reactions involve loss of electrons
Which fats spoil more readily? Why?
Polyunsaturated because their double bonds are unstable (monounsaturated are less susceptible)
Which fats are most resistant to oxidation
Saturated fats (least likely to become rancid)
3 ways manufactures can protect fat-containing products again rancidity:
1. Sealed air-tight, nonmetallic containers, protected from light and refrigerated
2. Add antioxidants to compete for the oxygen (ex. BHA and BHT and Vit E)
3. Hydrogenation
Define antioxidants
food additive, preservatives that delay or prevent rancidity of fats in foods and other damage to food cause by oxygen
Define hydrogenation
A chemical process by which hydrogens are added to monounsaturated or polyunsaturated fatty acids to reduce the number of doubly bonds, making the fats more saturate (solid) and more resistant to oxidation (protecting against rancidity). Process produces
How are trans-fatty acids produced
by hydrogenation
Cis
On the near side of; refers to a chemical configuration in which the H atoms are located on same side of double bond
Trans
on the other side of; refers to chemical configuration in which H atoms are on opposite sides of double bond
TRUE or FALSE: Total hydrogenation often occurs during food processing
False, most often fat is paritally hydrogenated
Two advantages of hydrogenation
1. Protects against oxidation (thereby, prolonging shelf life) by making polyunsaturated fats more saturated
2. Alters texture of foods by making liquid vegetable oils more solid (as in margarine - improves texture, makes more spreadable)
In nature most double bonds are cis or trans?
cis
Naturally occurring trans-fatty acids are found commonly where?
milk and meat
Conjugate linoleic acids
Naturally occurring fatty acids that have at trans configuration (may have health benefits).
Not counted as trans fats on food labels
Define conjugated linoleic acid
Several fatty acids that have the same chemical formula as linoleic acid (18-carbons, 2-double bonds) but with different configurations (the double bonds occur on adjacent carbons)
Phospholipids and sterols make up what percent of the lipids in the diet?
5%
Define phospholipid
A compound similar to a triglyceride but having a phosphate group (a phosphorus-containing salt) and choline (or another nitrogen-containing compound) in place of one of the fatty acids
the word ending -ase denotes an
Enzyme
Define Emulsifier
Substances with both water-soluble and fat-soluble portions that promote the mixing of oils and fats in watery solutions
Lecithin is what type/family of lipids
Phospholipids
Define choline
nitrogen-containing compound found in foods and made in the body from amino acid methionine. Choline is part of phospholipid lecithin and the neurotransmitter acetylcholine.
Relating to the chemical structure, how are phospholipids emulsifiers?
Fatty acids make them soluble in fat and the phosphate group allows them to dissolve in water
Riches food sources of phospholipids
In lechithin = eggs, liver, soybeans, wheat germ, peanuts
Phospholipids are soluble in
water and fat
Role of phospholipids in the body
1. help fat-soluble substances, including vitamins and hormones, pass easily in and out of cells
2. act as emulsifiers, helping to keep fats suspended in the blood and bodily fluids
Phospholipids are constituents of what in the body?
cell membranes
Where is lecithin made in the body
The liver
TRUE or FALSE: lecithin is an essential nutrient
FALSE, it is not an essential nutrient; it is just another lipid
Side effects of large doses of lecithin
GI distress, sweating, loss of appetite
How many kcalories per gram do lipids provide
9
Lecithin supplements, describe
Digestive enzyme lecithinase in intestine hydrolyzes most of it before it passes into the body, therefore little reaches the tissues. (supplement is useless :o )
Compounds made from cholesterol
#NAME?
Most famous sterol
Cholesterol
Sterols
compounds containing a four-ring carbon structure with any of a variety of side chains attached
Sterols are found
both plants and animals contain sterols
Most significant amounts of cholesterol (sterols) are found
from animals: eggs, fish, poultry, meats, and dairy products
Are "good" and "bad" cholesterols types found in foods?
No, the terms, "good" and "bad", refer to the way body transports cholesterol in the blood
Sterols other than cholesterol are naturally found
in plants
Plant sterols affect cholesterol absorption how
they interfere and inhibit it, lowers blood cholesterol levels
More than 90% of the body's cholesterol resides where
in the cells
Cholesterol made in the body is called
Endogenous
Cholesterol from outside the body (foods) is called
Exogenous
In the body, cholesterol is manufactured where and from what
#NAME?
How much cholesterol does the liver make
about 800-1500 milligrams per day
Plaque
an accumulation of fatty deposits, smooth muscle cells, and fibrous connective tissue that develops in the artery walls in atherosclerosis. Plaque associated with atherosclerosis is known as atheromatous plaque.
Atherosclerosis
Type of artery disease characterized by plaques (accumulations of lipid-containing material) on the inner walls of the arteries
Disease that causes heart attacks and strokes
Atherosclerosis
Lipids with a multiple-ring structure
Sterols
Hydrophobic
term referring to water-fearing, or non-water-soluble, substances; also known as lipophilic (fat loving)
Hydrophilic
water-loving, or water-soluble, substances
GI tract receives how many grams of triglycerides
50 - 100 grams
GI tract receives how many grams of phospholipids
4 - 8 grams
GI tract receives how many grams of choelsterol
200 - 350 grams
Fats are hydrophobic or hydrophilic?
Hydrophobic, they tend to separate from watery fluids of the GI tract
Fat digesting enzymes are hydrophobic or hydrophilic?
Hydrophilic
What is the goal of fat digestion
to dismantle triglycerides into small molecules that the body can absorb: namely monoglycerides, fatty acids, and glycerol
Monoglycerides
molecules of glycerol with 1 fatty acid attached
Diglycerides
A molecule of glycerol with 2 fatty acids attached
PH of the stomach is
just below 2
Enzyme that hydrolyzes lipids is called
lipase
lingual refers to
the tongue
When they reach body temperature fats...
melt
Where is lingual lipase released
through the salivary gland at the base of the tongue
In infants, which enzyme efficient digests the short- and medium-chain fatty acids found in milk
lingual lipase
T or F: Lingual lipase plays a minor role in fat digestion in adults and an active role in infants
TRUE
Muscle contractions of the stomach propel the stomach contents toward where
the pyloric sphincter
The churning of the chyme and partially digested food in the stomach as what effect of fat and digestion?
it grinds the solid pieces to finder particles, mixes the chyme, and disperses the fat into small droplets. These actions help expose the fat for attack by the gastric lipase enzyme
The gastric lipase enzyme performs best in what environment
acidic
Most of fat digestion takes place in the
small intestine
The acid-stable lingual lipase initiates lipid digestion how
by hydrolyzing one bond of triglycerides to produce diglycerides and fatty acids
Degree of hydrolysis by lingual lipase is slight for most fats but appreciable for what fats?
Milk fats
The stomachs churning action does what
mixes fats with water and acid
Gastric lipase accesses and hydrolyzes
only a small amount of fat
Bile contains
#NAME?
When fat enters the small intestine it triggers the release of what hormone
CCK : cholecysokinin
CCK signals what
gallbladder to release its stores of bile
Bile is made where
in the liver
Bile is stored
in the gallbladder
Bile acids are made from what
cholesterol
Amino acids are
building block proteins
Most hydrolysis of triglycerides occurs where in the body
small intestine
Major fat-digesting enzymes are
pancreatic lipases (some intestinal lipases are also active)
Bile acid + amino acid acts as
emulsifier, drawing fat molecules into surrounding watery fluids since amino acid end is hyrophilic and sterol end is lipophilic
Emulsification of fat by bile process:
1. In stomach -> fat and watery GI juices separate. Enzymes in GI juices can't get at the fat
2. Fat enters S.I. -> gallbladder secretes bile -> Bile has affinity for fat + water so brings fat into the water
3. Bile's emulsifying action converts large fat
Fat digestion in SI:
1. Bile flows from gallbladder
2. Fat -> Bile -> Emulsified fat
3. Pancreatic lipase flows from pancreas
4. Emulsified fat -> pancreatic (and intestinal) lipase -> monoglycerides, glycerol, fatty acids (absorbed)
Fat in the large intestine:
Some fat and cholesterol trapped in fiber exit in feces
Major fat-digesting enzymes
Pancreatic lipases
what do pancreatic lipases (enzymes) do to triglycerides
Remove one, then the other of each triglyceride's outer fatty acids, leaving a monoglyceride. Occasionally, enzymes remove all 3 fatty acids, leaving a free molecule of glycerol
Fatty acids, monoglycerides, and glycerol are absorbed where
into the intestinal walls
Lipids that can be absorbed as is
sterols (if any fatta cids are attached, they are first hydrolyzed off)
Two possible routes of bile after it enters SI and emulsifies fat:
1. Most of bile is reabsorbed from SI and recycled
2. Some trapped fiber in LI and excreted
Why does the excretion of bile effectively reduce blood cholesterol
because cholesterol is needed to make bile
Enterhepatic Ciculation
Cycle of bile being release into SI, reabsorbed, and the recycled (sent back for reuse)
(enteron = intestine , hepat = liver)
Micelles
tiny spherical complexes of emulsified fat that arise during digestion
What do most micelles contain
bile salts and products of digestion (fatty acids, monoglycerides, cholesterol)
Chylomicrons
class of lipoproteins that transport lipids from intestinal cells to the rest of the body
Short- and medium-chain fatty acids diffuse easily into intestinal cells and are absorbed where
directly into the bloodstream
Long-chain fatty acids and monoglycerides merge into spherical complexes known as
micelles
Emulsified fat droplets can be called
micelles
How are micelles formed
by molecules of bile surrounding monoglycerides and fatty acids
Micelles do what for lipids
they help create a configuration that permits solubility in watery digestive fluids and transportation (diffuse easily) into intestinal cells
What happens to lipid contents of micelles once inside intestinal cells
monoglycerides and long-chain fatty acids are reassembled into new triglycerides
Chylomicrons are released into where
by intestinal cells into lymphatic system
Following lymphatic entry where do chylomicrons go
glide through lymphatic system until they find the point of entry at the thoracic duct near the heart
The point of entry for chylomicrons into the blood stream is where
at the thoracic duct near the heart
Chylomicrons are
transport vehicles (lipids pack with protein into them)
Lipoproteins
transport vehicles for fats
- clusters of lipids associated with proteins that serve as transport vehicles for lipids in the lymph and blood
The more lipids the __ the density
lower
The more proteins the __ the density
higher
Four types of lipoproteins
1. Chylomicrons
2. VLDL (Very-Low-Density Lipoproteins)
3. LDL (Low-Density Lipoproteins)
4. HDL (High-Density Lipoproteins)
Largest and least dense of lipoproteins
chylomicrons
Within how many hours after absorption have most triglycerides been depleted
14 hours
After triglycerides have been depleted by absorption what remains
few remnants of protein, cholesterol, and phospholipid
What happens to Chylomicron remnants
special protein receptions on membranes of liver cells recognize and remove the remnants from blood -> liver cells dismantle them and either use or recycle pieces
Transports diet derived lipids (mostly triglycerides) from SI (via lymph system)
Chylomicrons
VLDL
Very low density lipoprotein
Type of lipoprotein made primarily by liver cells to transport lipids to various tissues in body
Composed primarily of triglycerides
LDL
Low-density lipoprotein
type of lipoprotein derived from VLDV as VLDL triglycerides are removed and broken down
Composed primarily of cholesterol
HDL
High-density lipoprotein
type lipoprotein that transports cholesterol back to the liver from the cells
Composed primarily of protein
Liver makes __ to remove cholesterol from the cells and carry it back to the liver for recycling/disposal
HDL
TIP
H = Healthy = HDL
L = Less Healthy = LDL
Reverse cholesterol transport or Scavenger pathway
transport of cholesterol from the tissues to the liver
The blood cholesterol linked to heart disease
LDL
Elevated HDL represents
cholesterol returning from the resto of the body to the liver for breakdown and excretion
Heart attack is associated with high __ cholesterol
LDL
Factors that lower LDL / raise HDL
#NAME?
The arrangement of hydrophobic molecules on the inside and hydrophilic molecules on the outside allows what
lipids to travel through the watery fluids of the blood
Lipoprotien that is half cholesterol
LDL
Lipoprotein that is half protein
HDL
Lipoprotein that is half triglycerides
VLDL
Chylomicrons contain mostly
triglycerides
Triglycerides role in the body
provide energy
Adipose tissue
The body's fat tissue; consists of masses of triglyceride-storing cells
Adipokines
Proteins synthesized and secreted by adipose cells
Essential fatty acids
fatty acids needed by the body but not made by it in amounts sufficient to meet physiological needs
Storage depot for fat
adipose tissue
Most body cells store how much fat
limited amounts
What hormone does adipose tissue actively secret
adipokines
What role do adipokens play
help regulate energy balance and influence several body functions
Essential nutrient
one that the body cannot make, or cannot make in sufficient quantities to meet its physiological needs
Obesity increases the release of what protein
adipokine (resistin)
Obesity decreases the release of what protein
adipokine (adiponectin)
Resistin does what in the body
promotes inflammation and insulin resistance - factors that predict heart disease and diabetes
Protein that protects again inflammation, diabetes, and heart disease
Adipokine (adiponectin)
Additional roles of fat
insulates the body
absorbs shock
provides structural material for cell membranes
participates in cell signaling pathways
Two fatty acids that the body can not make
Linoleic acids (18-carbon omega-6)
Linolenic acid (18-carbon omega-3)
Two essential fatty acids that must be supplied by the diet
Linoleic and linolenic fatty acids
Omega-3 and Omega-6 fatty acids most notably obtained from what foods
Vegetable oils, seeds, nuts, fish, and other marine foods
Conditionally essential
a nonessential nutrient (such as arachidonic acid) that must be supplied by the diet in special circumstances (as in linoleic acid deficiency)
Arachidonic Acid
omega-6 polyunsaturated fatty acid with 20 carbons and 4 double bonds
Present in small amounts in meat and other animal products and synthesized in the body from Linoleic acid
TIP
The body can not create omega-6 or -3 fatty acids from scratch nor convert an 6 to a 3 or vise versa
Cells can start with 18-carbon member of omega family and make longer fatty acids (forming double bonds/ desaturation) and lengthening the chain 2 carbons
EPA eicosapentaenoic (EYE-cossa-PENTA-ee-NO-ick)
omega-3 polyunsaturated fatty acid with 20 carbons and 5 double bonds
present inf atty fish and synthesized in limited amounts in the body from linolenic acid
Found in the eyes and brain and are essential for nomral growth and cognitive development
omega-3 fatty acids
DHA docosahexaaenoci acid (DOE-cossa-HEXA-ee_NO-ick)
omega-3 polyunsaturated fatty acid with 22 carbons and 6 double bonds
present in fatty fish and synthesized in limited amts in the body from linolenic acid
EPA and DHA plays an important role in treatment of
heart disease
Eicosanoids
derivatives of 20-carbon fatty acids
biologically active compounds that help to regulate blood pressure, blood clotting, and other body functions. they include prostaglandins, thromboxanes, and leukotrienes
How are eicosanoids different from hormones
1. They affect only cells in which they are made or nearby cells in same localized environment (hormones secreted in 1 location and travel to affect cells all over body)
2. They often have different effects on different cells (hormones elicit same respons
The body uses arachidonic acid and EPA to make substances known as
eicosanoids
EPA eicosanoids play what role in body health
help to lower blood pressure, prevent blood clot formation, protect against irregular heartbeats, reduce inflammation
TIP
eicosanoids actions sometimes oppose one another
Classic deficiency symptoms of fatty acids include
growth retardation, reproductive failure, skin lesions, kidney and liver disorders, subtle neurological and visual problems
Historically, infants and young children who have been fed fat-free milk and low-fat diets or hospital clients who have been provided no polyunsaturated fatty acids for long periods of time had what deficiency
fatty acid deficiencies
T or F: most diets in the US and Canada do not meet the minimum essential fatty acid requirements adequately
False, they do
Eicosinoids are powerful compounds that participate in (body)
blood pressure regulation, blood clot formation, immune response to injury and infections, etc
Why are deficiencies of essential fatty acids unlikely
they are common in the diet and stored in the body
Nutrient most linked with heart disease, some types of cancer, and obesity
Fat
Blood lipid profile
results of blood tests that reveal a person's total cholesterol, triglycerides, and various lipoproteins
Desirable blood lipid profile
- Total Cholesterol: __ mg/dL
- LDL Cholesterol: __ mg/dL
- HDL Cholesterol: __ mg/dL
- Triglycerides: __ mg/dL
< 200 mg/dL
<100 mg/dL
>= 60 mg/dL
<150 mg/dL
Reveals concentrations of various lipids in the blood, notably triglycerides and cholesterol, and their lipoprotein carriers (VLDL, LDL, HDL)
Blood lipid profile
Elevated blood cholesterol is a major risk factor for
Cardiovascular disease (CVD)
Cardiovascular Disease (CVD)
general term for all disease of the heart and blood vessels.
Atherosclerosis is the main cause of CVD
When the arteries that carry blood to heart muscle become blocked the heat suffers damage known as
Coronary heart disease (CHD)
Used to predict the likelihood of a person's suffering a heart attack or stroke
Blood cholesterol level
Much of the effort to prevent heart disease focuses on
lowering blood cholesterol
Cholesterol accumulating in arteries causes
restricted blood flow and raised blood pressure - consequences are deadly
Nation's number one killer of adults
heart disease
The more saturated fat in the diet the higher ___ cholesterol
LDL
____ Cholesterol raises the risk of heart disease
LDL
Most notable saturated fatty acids that raise blood cholesterol
Lauric
Myristic
Palmitic Acids
(12, 14, and 16 carbons respectively)
Saturated fatty acid that does not raise blood cholesterol
Stearic acid (18-carbons)
Major sources of saturated fats:
#NAME?
Products that contain tropical oils
Candies, pastries, pies, doughnuts, cookies
The average daily intake of trans-fatty acids in the US is
6 grams per day
Major sources of trans fats:
#NAME?
When selecting margarine look for:
- soft (liquid or tub) vs hard stick
- <= 2g saturated fat
- Liquid vegetable oil (not hydrogenated or partially hydrogenated) as first ingredient
- "Trans fat free
Eggs contain what amount of saturated fat and cholesterol
1 gram of saturated fat but just over 200 mg of cholesterol (2/3rds of the recommended daily limit)
Difference of Olestra's chemical structure
Made of sucrose molecule with 6-8 fatty acids attached