Lipids: Structure, Classification, and Function

Study Notes

Saturated Fatty Acids have a single carbon-carbon bond.
Unsaturated Fatty Acids have one to several double bonds.
Trans Fats are solid forms of fat, created through partial hydrogenation of oil.

Also known as tricylglycerols, where three hydroxyl groups of glycerol are esterified with fatty acids.
Properties: Physical State, Solid animal fats contain mainly saturated fatty acids, while Vegetable oils contain high amounts of unsaturated fatty acids.
Some unsaturated fatty acids (linoleic and linolenic acids) are essential fatty acids.
Oils with an average of more than one double bond per fatty acid chain are called polyunsaturated.
Melting points of fatty acids increase as the number of carbons in the hydrocarbon chains increases and as the number of double bonds decreases.
Triglycerides rich in unsaturated fatty acids are generally liquid at room temperature and are called oils.
Triglycerides rich in saturated fatty acids are generally semi-solids or solids at room temperature and are called fats.

Hydrogenation is the source of trans fatty acids, adding hydrogen across the carbon-to-carbon double bond in an unsaturated fatty acid.
Saponification is the base-promoted hydrolysis of fats and oils in aqueous NaOH, producing glycerol and a mixture of fatty acid salts called soaps.

Phospholipids contain an alcohol, two fatty acids, and a phosphate ester.
Glycerophospholipids have glycerol as the alcohol, while sphingolipids have sphingosine.
Glycolipids contain a carbohydrate, or sugar, residue.

Polar (hydrophilic) head groups are in contact with the aqueous environment.
Nonpolar (hydrophobic) tails are buried within the bilayer and shielded from the aqueous environment.
Glycerophospholipids, also called phosphoglycerides, are the second most abundant group of naturally occurring lipids.

Insoluble in water, soluble in non-polar solvents and solvents of low polarity.
Derived from the Greek word 'lipos', meaning fat.
Have higher energy density than carbohydrates.
Heterogeneous group of compounds related to fatty acids, fats, oils, waxes, and other related substances.
Yield fatty acids upon hydrolysis, which are utilized by living organisms.

By function: Storage, Membrane Components, Messengers
By type: Simple Fats and Oils (Triacylglycerols), Waxes, Fats, Oils, Complex Phospholipids, Glycolipids, Lipoproteins, Other Complex Lipids (Steroids, hormones derived from cholesterol)