Post on 24-Apr-2015
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Chapter 5: Lipids
Overview
Structure: Saturated vs non-saturated FA Classification: Essential vs non-essential Classes: TG, phospholipids, sterols Functions Digestion and absorption Transport Foods and diet patterns
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
Building blocks of lipids Saturated Unsaturated
Monounsaturated Polyunsaturated
Fatty Acid Structure
Methyl group Acid
group(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
Methyl group Acid
group(omega end) (alpha
end) Saturated Fatty Acid C18:0
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
Methyl group Acid
group(omega end) (alpha
end) One double bond C18:1
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
Methyl group Acid
group(omega end) (alpha
end) > 2 double bonds C18:2
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
Chain Length & Saturation: Fatty Acid Characteristics
Long chain…> 12 C Medium chain …6-10 C Short chain…< 6 C
Saturated Unsaturated
Unsaturated Fats
Fewer H atoms; double bonds between Carbons Usually liquid at room temp Mostly plant and fish sources More chemically active (turn rancid faster) Lower blood cholesterol Monounsaturated fat (MUF) - 1 double bond
(minus 2 H) Polyunsaturated fat (PUF) - 2 or more double
bonds
Saturated Fats
Maximum # of Hydrogen atoms Usually solid at room temp. Mostly from animal sources (meat & dairy) Exceptions - tropical oils (palm, coconut)
very saturated Raise blood cholesterol
Essential Fatty Acids
Cannot be produced by the body Omega-3 & Omega-6 fatty acids
Essential for immune function, vision, cell membrane, and production of hormone-like compounds
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
Fish oil is important source Also found in canola, soybean oil & nuts Eicosapentaenoic acid (EPA) and
docosahexaenoic acid (DHA) Recommendation: eat fish 2 x per week Decreases blood clot formation Lowers risk of heart disease
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 Arachidonic acid
Need about 1 tablespoon daily Increases blood clotting Increases inflammatory responses
Signs and Symptoms of Essential Fatty Acids Deficiency
Flaky, itchy skin Diarrhea Infections Growth retardation Poor wound healing Anemia
Functions of Lipids Concentrated energy (diet and storage) Provides essential FAs Insulation for body Padding around organs Transport fat-soluble vitamins Contribute to satiety Flavor and mouth feel of foods Present in cell membranes
Triglycerides (TGs)
Most lipids in foods and body in form of TGs (95%)
Chemical structure: Glycerol back bone 3 fatty acids (Fas) FA 4-22 C long; usually 16-20 C
Triglycerides
(condensation reaction)
Glycerol + 3 FA’s Triglyceride +
3 H20
H O
H--C--O--C--
O
H--C--O--C--
O
H--C--O--C--
H
Fatty Acid
Fatty Acid
Fatty Acid
+
H O
H--C--O--C--
O
H--C--O--C--
O
H--C--O--C--
H
Fatty Acid
Fatty Acid
Fatty Acid
Triglycerides
Function of Triglycerides
Concentrated energy (diet and main storage form) Provides essential fatty acids (linoleic; linolenic) Carrier of Fat Soluble Vits (A,D,E,K) Body Insulation & padding around organs Cell membranes Adds flavor & texture to foods Contributes to satiety
Phospholipids
Built on glycerol backbone > 1 FA replaced with P containing
compound Cell membranes Help transport other fats in blood Emulsifier in foods Mix with both water and fat
Chemical forms of Phospholipid
Sterols
Multi-ringed structures; noncaloricDo not dissolve in water wellex. cholesterol & Vitamin D
Two sterols
Function of Cholesterol
Cell membranes Precursor for Vit D & some hormones (estrogen,
testosterone) Major component of bile ONLY FOUND IN ANIMALS; NEVER FOUND
IN PLANTS Not an essential nutrient since it’s made in body Produced by the liver
Cell membranes