Dr.ehab the lipids triglycerides, phospholipids, and sterols

The Lipids: Triglycerides,

Phospholipids, and Sterols

carbohydrates, fatty acids and

triglycerides are composed of

carbon (C), hydrogen (H), and

oxygen (O).

Because these lipids have

many more carbons and

hydrogens in proportion to

their oxygens, however, they

can supply more energy per

gram than carbohydrates

Triglyceride contains one

molecule of glycerol and

three fatty acids

Fatty acids may be saturated

or unsaturated

Fatty acids may be 4 to 24

(even numbers of) carbons

long, the 18-carbon ones

being the most common in

foods

The 18-carbon fatty acids that

fit this description are linolenic

acid (omega-3) and linoleic

acid (omega-6).

Stearic acid, an 18-carbon saturated fatty acid

Stearic acid

Oleic acid, an 18-carbon monounsaturated fatty acid

Linoleic acid, an 18-carbon polyunsaturated fatty acid

Condensation of Glycerol and Fatty Acids to

Form a Triglyceride

Comparison of Dietary Fats

Most fats are a mixture of saturated,

monounsaturated, and polyunsaturated fatty

acids.

phospholipid is lecithin

cell membrane is made of phospholipids

A Bile Acid

bile acids the liver makes from cholesterol. It

is then bound to an amino acid to improve its

ability to form micelles, spherical complexes

of emulsified fat. Most bile acids occur as bile

salts, usually in association with sodium, but

sometimes with potassium or calcium

Emulsification of Fat by Bile

Digestion (Hydrolysis) of a Triglyceride

Chylomicrons

VLDL (Very-Low-Density Lipoproteins)

LDL (Low-Density Lipoproteins)

HDL (High-Density Lipoproteins)

Absorption of Fat The end products of fat digestion

are mostly monoglycerides, some

fatty acids, and very little glycerol.

Their absorption differs depending

on their size. (In reality, molecules

of fatty acid are too small to see

without a powerful microscope

Sizes and Compositions of the Lipoproteins

Cholesterol in Selected Foods

Sources of Omega-3 and Omega-6 Fatty Acids

The USDA Food Guide amounts of fats that

can be included as discretionary kcalories

when most food choices are nutrient dense

and fat 30% total kcal:

• 11 g for 1600 kcal diet

• 15 g for 1800 kcal diet

• 18 g for 2000 kcal diet

• 19 g for 2200 kcal diet

• 22 g for 2400 kcal diet

For perspective, 1 tsp oil = 5 g fat and

provides about 45 kcal