Lipids

Lipids are compounds that are soluble in ether, benzene, hot alcohols, etc. They are not soluble in water.

Classification:

Neutral Lipids
Triglycerides
Waxes

True waxes
Cholesterol esters
Vitamin A esters
Vitamin D esters

Conjugated lipids

Phospholipids - contain a molecule of phosphoric acid and a fat molecule

Cerbrosides - contain a carbohydrate and a lipid

Sulfolipids - contain sulfur

Derived lipids

Fatty acids
Fatty alcohols
Fatty aldehydes
Hydrocarbons
Vitamins A, D, E, and K

Miscellaneous

Soaps
Coloring matters
Oxidative polymers
Thermal polymers etc.

Triglycerides

The alpha positions correspond to the locations of the R1 and R3 fatty acids while the beta position is where the R2 fatty acid is located. In the newer system of nomenclature:

SN1 is R1

SN2 is R2

SN3 is R3

In many respects the alpha positions ( SN-1, SN-2 ) are not identical in composition, chemical reactivity or affect on physical properties of the glyceride molecule.
Phospholipids

Waxes Long chain alcohol and fatty acid.

R' = 15, R=17, Cetyl stearate.

Vitamin A and D esters may be wax like.

Cholesterol

International Units: Provides a basis for comparing the vitamin activity of different compounds that exhibit that activity. For example carotene and retinol both exhibit vitamin A activity. One international unit, I.U., of vitamin A is equivalent to the activity of 0.3 micrograms of retinol.


Vitamin A

Functions in vision and maintenance of epithelial tissue

Vitamin D

Functions in the absorption of calcium and phosphorus

Vitamin E

No known function in man

Vitamin K


Involved in normal blood clotting

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Melting Points

• Increasing carbon chain length, increases the melting point

  • Butyric 7.9°C

    Lauric 44.2°C

    Stearic 69.6°C

    Behenic 79.7°C

• Odd chain fatty acids usually melt at a lower temperature than do the even chain acids containing one less carbon. Increasing the number of double bonds decreases the melting point:

  • Stearic 69.6°C

    Oleic 13.4°C

    Linoleic -5.0°C

    Linolenic -11.0°C

• Increasing the distance of the double bond from the carboxyl group, decreases the melting point
• Trans isomers have higher melting points
• Methyl side chains lower the melting point
• Conjugated double bonds have higher melting points

Properties of some common fatty acids:

Types of Fat

Milk Fat
Cow Other
Lauric Acid Oils
Coconut Palm Kernel Others
Vegetable Butters
Cocoa Butter Other
Animal Fats
Lard Greases Tallow
Oleic - Linoleic
Cotton Seed Corn Peanut Safflower Olive Palm
Sunflower Others
Linoleic
Linseed Soybean Others

Milk Fats
Derived from cows and other milk producing animals. Larger amounts of fatty acids in the range of C4 to C12 than found in any other type of fat. Tends to be fairly highly saturated. Has a characteristic and desirable flavor.

Animal Depot Fats: Contain large amounts of saturated C16 and C18 fatty acids (30%)

Lard Fatty Acid Content

Oleic - Linoleic Oils

Soybean oil

Vegetable Butters

Lauric Acid Oils