ECDA, MDAugust 2009

LIPIDS

Lipids are important structural elements of biological cell membranes. And like carbohydrates, they are important sources of energy.

Lipid molecules may be classified as fatty acids, cholesterols, glycerides, phospholipids, phosphoglycerides, and glycolipids.

LIPIDS

LIPID BILAYER

PHOSPHOLIPIDS

FATTY ACIDS

FATTY ACIDS

Fatty Acids, as components of phospholipids, are important structural elements of cell membranes.

They can be converted to great amount of energy once hydrolyzed or metabolized.

FATTY ACIDS Fatty acids are mainly derived from the

diet. 30%-40% of the calories ingested each day

in the average human diet are provided by the fatty acid components or triacylglycerols and phospholipids.

Because of the relationship between a diet high in fat and heart disease, Heart Associations throughout the world recommend that no more than 30% of the calories in our diet be derived from fatty acids

FATTY ACIDS

Dietary lipids are degraded by lipases and phospholipases, which are enzymes secreted into the intestinal lumen from the pancreas.

If the diet does not provide sufficient lipid to satisfy immediate needs, the fatty acids stored in the adipose tissues in the form of triacylglycerols may be required.

FATTY ACIDS

Fatty acids may be classified as either saturated or unsaturated

Saturated fatty acids are long carbon chains with no double bonds linked to carbon atom

Unsaturated fatty acids, on the other hand, has 1 or more double bonds linked to carbon atoms

FATTY ACIDS

Saturated Fatty Acids

Common Name Formula Abbreviation

Lauric Acid CH3(CH2)10COOH 12:0

Myristic Acid CH3(CH2)12COOH 14:0

Palmitic Acid CH3(CH2)14COOH 16:0

Stearic Acid CH3(CH2)16COOH 18:0

Arachidic Acid CH3(CH2)18COOH 20:0

Unsaturated Fatty Acids

FATTY ACIDS

Common Name Formula Abbrev.

Lauroleic Acid CH3CH2CH=CH(CH2)7COOH 12:1Δ9

Myristoleic Acid CH3(CH2)3CH=CH(CH2)7COOH 14:1Δ9

Palmitoleic Acid CH3(CH2)5CH=CH(CH2)7COOH 16:1Δ9

Oleic Acid CH3(CH2)7CH=CH(CH2)7COOH 18:1Δ9

Linoleic Acid CH3(CH2)4CH=CHCH2CH=CH(CH2)7COOH 18:2Δ9,12

Linolenic Acid CH3CH2CH=CHCH2CH=CHCH2CH=CH(CH2)7COOH 18:3Δ9,12,15

Arachidonic Acid

CH3(CH2)5CH=CHCH2CH=CHCH2CH=CHCH2CH=CH(CH2)

3COOH20:4Δ5,8,11,14

FATTY ACIDS Linoleic, linolenic, and arachidonic acids

are essential fatty acids and are denoted by another short hand notation based on the omega system

Omega system denotes the methyl carbon (terminal sp3-hybridized carbon) as the omega (ω) carbon.

○ Linoleic acid as 18:2ω6○ Linolenic acid as 18:3ω3○ Arachidonic acid as 20:4ω6

FATTY ACIDS Unsaturated fatty acids are very reactive

substancesThese molecules are easily hydrogenated,

halogenated, and oxidized because of double bonds

Polyunsaturated fatty acids are also susceptible to peroxidation and will react readily with molecular oxygenThis results in the development of undesirable

flavors and color or production of food with low nutritive value, or may lead to formation of toxic products.

FATTY ACIDS

Unsaturated fats do not raise blood cholesterol. Foods with unsaturated fats include olives, avocados, fatty fish, like salmon, and most nuts. Olive, canola, sunflower, soybean, corn, and safflower oils are high in unsaturated fats.

Even though unsaturated fats don't raise blood cholesterol, all types of fat are high in calories and should be eaten in limited amounts.

FATTY ACIDS

GLYCEROLS

GLYCEROLS

Glycerol, also commonly called glycerin or glycerine, is a colorless, odorless, viscous liquid that is widely used in pharmaceutical formulations.

Glycerol is a precursor for synthesis of triacylglycerols and of phospholipids in the liver and adipose tissues. When the body uses stored fat as a source of energy, glycerol and fatty acids are released into the bloodstream.

GLYCEROLS Glycerol is a sugar

alcohol also, and has three hydrophilic alcoholic hydroxyl groups that are responsible for its solubility in water and its hygroscopic nature.

GLYCERIDES

GLYCERIDES Glycerides, more correctly known as

acylglycerols, are esters formed from glycerol and fatty acids

Glycerol has three hydroxyl functional groups, which can be esterified with one, two, or three fatty acids to form monoglycerides, diglycerides, and triglycerides, respectively.

Two types:○ 1. partial glycerides

- A. Monoglycerides- B. Diacylglycerols

○ 2. triglycerides

GLYCERIDES

monoglyceride diglyceride

GLYCERIDES

triglyceride

GLYCERIDES

Glycerides are important nutritionally, being the storage form of fats in cells

The most abundant fatty acid in natural glycerides are palmitic, stearic, oleic, and linoleic acids.

GLYCERIDES

The ester groups of this class of lipids may be cleaved by alkali, acid or enzymes.Alkali hydrolysis in vitro is called

saponification producing soaps in the process. The reaction is shown

RCOOH + NaOH RCOO- Na+ + ROH

SAFONIFICATION

GLYCERIDESEnzymatic hydrolysis can be effected by lipases

or phopholipases which breaks ester bonds to release the free fatty acid. This process is an important requisite for the utilization or mobilization of stored fats.

Nomenclature:○ All glycerides are named as derivatives of

glycerol.○ The carbons of glycerol are numbered 1 to 3 from

top to bottom.○ The fatty acyl substituent are mentioned in 1 to 3

order.

HYDROLYSIS

QUESTIONS

GLYCERYL ETHERS

Glyceryl ethers are rare lipids and are mostly found in neoplasms or cancer cells in the body

The main feature of the glyceryl ethers is the presence of an ether linkage between fatty acid and glycerol