Lipids

TriglyceridesPhospholipids

Sterols

Lipids• Lipids are a class of nutrients that includes:

– Triglycerides (fats and oils)– Phospholipids – Sterols– Waxes

• Composed of carbon, hydrogen, and oxygen.

• Lipids are hydrophobic (insoluble in water)

Characteristics of Lipids

• Composed of Carbon, Hydrogen, and Oxygen

• Greater than 2:1 ratio of H:O• Includes fats, oils, phospholipids, and

cholesterol• Building blocks are fatty acids and

glycerol.• Energy storage molecules• Phospholipids part of cell membrane

Fatty Acid Structure

•Carboxyl group (COOH) forms the acid.•“R” group is a hydrocarbon chain.

A Representative Fatty Acid

Fatty Acids• Fatty acids vary in carbon chain lengths, degree

of unsaturation, and number of double bonds. – Degree of Saturation- Saturation affects the

physical characteristics of the fat and its storage properties

Saturated vs. Unsaturated• Saturated - Saturated fatty acids carry the maximum

possible number of hydrogen atoms.

• .

Stearic acid, an 18-carbon saturated fatty acid

Saturated vs. Unsaturated• Unsaturated – Unsaturated fatty acids have

at least one double bond. There are 2 types– Monounsaturated fatty acid (MUFA)

Oleic acid, an 18-carbon monounsaturated fatty acid

Saturated vs. Unsaturated

• Polyunsaturated fatty acids (PUFA)– have at least two double bonds.

Linoleic acid, an 18-carbon polyunsaturated fatty acid

Saturated and Unsaturated Fatty Acids Help Shape Foods

SaturatedFatty Acid

UnsaturatedFatty Acid

Glycerol

An alcohol composed of a three carbon chain.

Synthesis of a Fat

Triglycerides

• TG (fats and oils) – composed of 3 fatty acids attached to a glycerol

TG

PhospholipidsPhospholipids

• contain glycerol, 2 fatty acids and a phosphate

group.

• Soluble in both water and fat

• Roles of phospholipids

– Transport lipids through Plasma membrane

– Make up the cell membrane

Phospholipids

Sterols• Sterols

– cholesterol, vit D, testorone– Multiple carbon-ring structure.– Found in plant and animal foods– Cholesterol is found in animal foods only -

meat, eggs, fish, poultry and dairy products

Sterols• Roles of sterols

– Needed to make bile acids, sex hormones, adrenal hormones and vitamin D

– Component of cell membranes– Cholesterol forms deposits in the

artery wall causing artherosclerosis.

Sterols