Chap. 5: Lipids. Properties of Lipids Do not readily dissolve in water Fats are solid at room...
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Transcript of Chap. 5: Lipids. Properties of Lipids Do not readily dissolve in water Fats are solid at room...
Chap. 5: Lipids
Properties of Lipids
Do not readily dissolve in water
Fats are solid at room temperature
Oils are liquid at room temperature
Triglycerides are the main form of lipids in food and body (storage)
Energy dense (9 kcal /gm)
Fatty Acids
Basic Form of Fats
Form together to make use for the body and for foodSaturatedUnsaturatedPolyunsaturated
Fatty Acid Structure (Fig. 5-1-A)
omega end alpha end
degree of saturation
H H H H H H H H H H H H H H H H H O
H-C--C--C--C--C--C--C--C--C--C--C--C--C--C--C--C--C-C-OH
H H H H H H H H H H H H H H H H H
Saturated Fatty Acid Structure (Fig. 5-1-A)
omega end alpha end
degree of saturation: single carbon bond
H H H H H H H H H H H H H H H H H O
H-C--C--C--C--C--C--C--C--C--C--C--C--C--C--C--C--C-C-OH
H H H H H H H H H H H H H H H H H
Monounsaturated Fatty Acid Structure (Fig. 5-1-B)
omega end alpha end
One double bond
H H H H H H H H H H H H H H H O
H-C--C--C--C--C--C--C--C--C=C--C--C--C--C--C--C--C--C-OH
H H H H H H H H H H H H H H H H H
Polyunsaturated Fatty Acid Structure (Fig. 5-1-C)
omega end alpha end
> 2 double bonds
H H H H H H H H H H H H H O
H-C--C--C--C--C--C=C--C--C=C--C--C--C--C--C--C--C--C-OH
H H H H H H H H H H H H H H H H H
Essential Fatty Acids
Body can only make double bonds after the 9th carbon from the omega end
Primarily need Omega-3 and Omega-6
Essential Fatty Acid- Omega-3 (alpha-linolenic acid)
omega end alpha end
1st double bond is located on the 3rd carbon from the omega end
H H H H H H H H H H H H H H H H H O
H-C--C--C=C--C--C =C--C--C=C--C--C--C--C--C--C--C--C-OH
H H H H H H H H H H H
Omega-3 Fatty Acid
Primarily from fish oil
Also found in canola or soybean oil
Recommend intake of ~2 servings of fish per week
(Omega-3)Alpha-linolenic acid
decrease blood clotting reduces heart attackexcess may cause hemorrhagic stroke large amounts may decrease inflammation
pain with rheumatoid arthritis
Essential Fatty Acid- Omega-6 (alpha-linoleic acid)
omega end alpha end
1st double bond is located on the 6th carbon from the omega end
H H H H H H H H H H H H H O
H-C--C--C--C-- C--C =C--C--C=C--C--C--C--C--C--C--C--C-OH
H H H H H H H H H H H H H H H H H
Omega-6 Fatty Acid
Found in vegetable oils
Only need ~ 1 tablespoon a day
Linoleic acid (Omega-6)Arachidonic acid
increase blood cot increase inflammatory responses
Fats in the body/food
TriglyceridesMain form of fats in the body and in food
PhosolipidsManufactured by the liver (not essential)
SterolsManufactured by the liver and in food
Differ based upon structure & function
Triglycerides
Structure:3 fatty acids connected to a glycerol
backbone
Function:Main form of fats in food and bodyTaken up my muscles for energyTaken up by adipose tissue for storage
Triglycerides
(Ester bond)
Glycerol + 3 FA’s Triglyceride +
3 H20
H
H--C--OH
H--C--OH
H--C--OH
H
O
HO-C-R
O
HO-C-R
O
HO-C-R
+
H O
H--C--O--C--
O
H--C--O--C--
O
H--C--O--C--
H
R + H2O
R + H20
R + H20
Phospholipid
Structure:Built on a glycerol backboneHas at least one fatty acid replaced with
phosphorus compound
Function: EMULSIFICATIONNeeded for transport of triglycerides and
sterols Needed for breakdown of triglycerides
inside the cellPart of the cell membrane
Functions of Phospholipids cont.
Emulsifier Bile acidsLecithins Improves food products
Emulsifier
Hydrophilic end (attracts water)
Hydrophobic end (attracts lipid)
Emulsification
Sterol--Cholesterol
Structure:A multi-ringed structureDo not have a glycerol backboneWaxy substance
Function:Needed for cell structureNeeded for bile and hormone production
Digestion
Digestion of Fat in the Stomach
Gastric lipase works only on triglycerides containing short & medium chain fatty acid
Minimal digestion in the stomach
Digestion of Fat in the Small Intestine
Primary site of fat digestionCCK stimulates pancreas to release pancreatic lipaseBile acid emulsifies digested fatFat is broken down to monoglycerides and fatty acids
Absorption of Fat
Short and medium chain (<12 C) fatty acids are water solubleEnters the portal system
Long chain fatty acids reforms into TGEnters the lymphatic system
Carrying Fat in the Bloodstream
Water (blood) and oil (fat) are incompatible
Unique system of fat
transportation is needed Fat
Transportation of Digested Fat
Re-formed triglycerides are packaged into a lipoprotein called chylomicrons
Enters Lymphatic System
Enzymes in the chylomicrons break down triglycerides
Fatty acids are absorbed by cells (i.e. muscles or adipose)
Lipoproteins
Transportation of Synthesized Fat
LIVER: takes up lipids from bloodManufactures fats (lipids) and cholesterolSynthesizes new lipoproteins and releases
them into the blood stream
LIPOPROTEINS produced by the liver
VLDL becomes more dense as it releases lipid to cells;
turns into LDL carries and releases fat
LDL carries and releases cholesterol and protein
HDL Cleans up loose cholesterol in the blood High proportion of protein
Benefits of HDL
Remove cholesterol from the blood stream
HDL may block oxidation of LDL
Reduce risk of heart disease
Pre-menopausal women have higher HDL
Good vs Bad Cholesterol
CVD increases with low HDL
If LDL not cleared from bloodstream, WBC’s take it to the arteries
Eventual build up of cholesterol in BV
Leads to CVD
Functions of Lipids (a recap)
Provide energy (muscles)
Efficient storage of energy (in adipose)
Insulation/Protection
Transport fat-soluble vitamins
Satiety
Flavor and mouth feel
Lipids in Foods
Hidden Fat
Look on the Nutrition Facts
Look on the lists of ingredients
Control portion size
Reduce-Fat Foods
Total energy is about the same
Sugar is commonly added in place of fat
Hydrogenation of Fatty Acids
Process used to solidify an oilAddition of H to C=C double bondsIncreases shelf lifeDecreases rancidityFormation of trans fatty acid (similar to shape of saturated fatty acid)
Health Dangers of Excessive Trans Fatty Acid
Raises LDL
Lowers HDL
Increases risk for heart disease
Current intake is~3% of total kcals
Soon to be on food labels
Where do we get Trans Fatty Acids?
hydrogenated fats
deep-fried foods
baked goods
non-dairy creamers
Rancidity
Decomposed oils
Breakdown of the C=C double bonds by ultraviolet rays, &/or O2
Yields unpleasant odor and flavor
PUFA more susceptible
Limits shelf life
RecommendationEssential fatty acids:2 servings of fatty fish/wk2-4 Tbls. of plant oil
~ 20-35% of total caloric intakeCurrent diet supplies ~33% of total kcal
from fatmuch from animal, whole milk, pastries,
cheese, margarine, and mayo
The American Heart Association
For high risk individuals
<20-30% of total kcal from fat/day
<7-10% from saturated fat (includes trans fatty acid)
<200-300 mg cholesterol a day