LIPIDS

Lipids

• diverse group of organic compounds that are primarily hydrophobic or amphipathic

• water-insoluble organic biomolecules that can be extracted from cells and tissues non-polar solvents

Benzene, chloroform, ether

Non-polar solvents:

Lipids

• esters of glycerol and fatty acids

• found in most plants and animals

Plants

• mainly occur in seeds and fruits

animals

• found in adipose tissue, bone marrow, and nerve tissue

Alcohols

• found in lipid molecule may be saturated

Fatty acids

• long organic acids having 4 - 30 carbons

• have single carboxyl group and long, nonpolar hydrocarbon tail

4 - 30 carbons

• how many carbon atoms in fatty acids?

Triglycerides

glycerol + 3 fatty acids = ???

Saturated fatty acids

• no double bonds between carbon atoms

• typically, solid at room temperature (e.g., butter)

• mainly obtained through dietary intake of animal fats

Unsaturated fatty acids

• one or more double bonds

• liquid at room temperature

Monounsaturated fatty acid (MUFA)

• one double bond in fatty and chain

Oleic Acid

• help reduce bad cholesterol levels (LDL)

Polyunsaturated Fatty Acid (PUFA)

• multiple double bonds

Omega-3 fatty acid

• essential fatty acid

Omega-6 fatty acid

• essential, but generally more prevalent in the diet

Simple Lipid

• esters of fatty acid and alcohols

• formed by condensation of alcohols and acids

Fats and oils

• found in all living cells

• insoluble in water and soluble in organic solvent

Waxes

• long-chain fatty acids esterified to long-cgain alcohols

• provide protective coating and waterproofing

Compound lipid

• molecules which consist of glycerol and fatty acid join with other organic molecule such as carbohydrate, protein, and amino acid

Phospholipid and glycolipid

Categories of Compound Lipid:

Phospholipid

• class of lipids whose molecule has hydrophilic “head” containing phosphate group, and two hydrophobic “tails”

• derived from fatty acids, joined by an alcohol residue

• key components of all cell membranes

• can form lipid bilayer

Glycolipids

• lipids with carbohydrate attached by glycosidic (covalent) bond

• role is to maintain stability of cell membrane and facilitate cellular recognition

Derived Lipids

• hydrolysis product of simple and compound lipids

Steroids

• hydrophobic and insoluble in water

• have structure composed of four fused rings

Phytosterols (stigmasterol)

• sterols of plants

Zoosterols (Cholesterol)

• sterols of animals

Ergosterol

• present in cell membrane of fungi and protozoa

Cholesterols

• widely distributed in all cells and is major component of cell membrane and lipoproteins

• helps in maintenance of body temperature and protect internal organs

Terpenoids

• also called as isoprenoids

• large and diverse class of naturally occurring organic chemicals dervived from 5-carbon compound isoprene and isoprene polymer called terpenes

Terpenoids

• several are biologically active and are exploited in the fight against cancer, malaria, inflammation