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