LIPIDS by Endang AstutiChemistry Department

Lipids can be considered to be biological molecules which are soluble in organic solvents, such as chloroform/methanol and are sparingly soluble in aqueous) solutions.

Their are three major classes of lipids: TriglyseridesPhospholipidssteroids

Energy storage• Fates stored in adipose tissue

Cell membrane structure• Creates a barrier for the cell.• Controls flow of materials.

Hormones and Vitamins• Hormones-communication between cells.• Vitamins-assist in the regulation of biological processes.

Lipid functions

1. Structure of fatty acids

Fatty acids have a long hydrocarbon chain with a terminal carboxylic acid group. Most of fatty acids have an even number of carbon atoms in an unbranched chain.Saturated fatty acids have no-double bonds between the carbon atoms, whereas mono- and polyunsaturated fatty acids have one or more double bonds.The properties of a fatty acid depend on the chain length and the number of double bonds.

Fatty acids are long unbranched chains of carbon atoms.

A carboxyl (-COOH) group at one end gives the molecule its acidic properties.

Most naturally occurring fatty acids contain an even number of carbon atoms in their backbone chains. Although a few with odd numbers are found in all organisms, these make up only a minor fraction of the total.

Stearic acid

Oleic acid

COMMON BIOLOGICAL SATURATED FATTY ACIDS

Symbol common name systematic name structure mp( )℃

12:0 Lauric acid dodecanoic acid CH3(CH2)10COOH 44.2

14:0 Myristic acid tetradecanoic acid CH3(CH2)12COOH 52.0

16:0 Palmitic acid Hexadecanoic acid CH3(CH2)14COOH 63.1

18:0 Stearic acid Octadecanoic acid CH3(CH2)16COOH 69.6

20:0 Arachidic aicd Eicosanoic acid CH3(CH2)18COOH 75.4

COMMON BIOLOGICAL UNSATURATED FATTY ACIDS

Symbol common name systematic name structure mp

16:1D9 Palmitoleic acidHexadecenoic acid CH3(CH2)5CH=CH-(CH2)7COOH -0.5

18:1D9 Oleic acid 9-Octadecenoic acid CH3(CH2)7CH=CH-(CH2)7COOH 13.4

18:2D9,12 Linoleic acid 9,12 -Octadecadienoic acid CH3(CH2)4(CH=CHCH2)2(CH2)6COOH -9

18:3D9,12,15 a-Linolenic acid9,12,15 -Octadecatrienoic acid CH3CH2(CH=CHCH2)3(CH2)6COOH -17

Reaction of fatty acid

2. triglyceride Ester of glycerol and a fatty acid.Principal functions is energy storage-fat.

May have 1-3 fatty acids which can each be different.

1-monoglycerid 2-diglyceride 3-triglycerid

CHOH

CH2OH

CH2OH

+ (R1,R2,R3 ) C

O

OH CH

H2C

H2C

O

O

O C

C

C

O

O

OR2

R1

R3

+ 3H2O

Examples of triglyceride

Sucrose Polyester, SPE

Physical Properties of glyceride Solubility Generally, triglycerides are completely nonpolar, with no affinity for water. But, since bi- or mono-glyceride consist of a polar or hydrophilic head and one or two nonpolar or hydrophobic tails , they are called amphiphilic and can be used as emulsifier. Melting Point Depending on chain length and number of double bond .

1. Saponification

Chemical Properties of triglyceride

Saponification Number The number of milligrams of KOH required to saponify 1g of fat; an approximate measure of the average molecular weight of a fat.

2. Alcoholysis

H 2C O O C R

H 2C O O C R ''

H C O O C R '+ 3 C H 3O H

C H 2O H

C H 2O H

C H O HR (R ',R '')C O O C H 3+ ¼î ÐÔ ß»¯¼Á

3. hydrolysis

CHOH

CH2OH

CH2OH

+ (R1,R2,R3 ) C

O

OH CH

H2C

H2C

O

O

O C

C

C

O

O

OR2

R1

R3

+ 3H2O

4. Halogenation or hydrogenation

Iodine number

5. Rancidity

Acid number

3 Phosphoglycerides

Lipids that contain a phosphate group.

Modified fat

Phosphate replaces on fatty acid chain.

Uses

Production of cell membranes.

Emulsifying agents.

CH2OH

C

CH2OH

HHO

1

2

3

Á¢Ìå רһ±àºÅ

Stereospecific numbering

CH2OH

C

H2C

HHO

O P

O

O£

O£

Phospho-glycerol

H2C

C

H2C

HO

O P

O

O£

O£

O C

O

R1

C

O

R2

phosphatidic acid

H2C

C

H2C

HO

O P

O

O

O£

O C

O

R1

C

O

R2

X

Phosphoglycerides

Nonglycerol lipids

Sphingomyelin

Sphingolipids Example

Glycosphingolipids

4. sterols

123

45

678

910

1112

13

14 1516

17

Cyclopentane Phenanthrene Cyclopentanoperhydro-phenanthrene

CholesterolCholesterol is a waxy, fat-like compound that belongs to a class of molecules called steroids. It's found in many foods, in your bloodstream and in all your body's cells. If you had a handful of cholesterol, it might feel like a soft, melted candle. Cholesterol is essential for: Formation and maintenance of cell membranes

(helps the cell to resist changes in temperature and protects and insulates nerve fibers)

Formation of sex hormones (progesterone, estradiol , testosterone)

Production of bile salts, which help to digest food Conversion into vitamin D in the skin when

exposed to sunlight.

Most of the body's cholesterol is manufactured in the liver.

• The formation of cholesterol involves a series of complicated biochemical reactions that begin with the widespread 2-carbon molecule Acetyl CoA.

• Cholesterol is made primarily in your liver (about 1,000 milligrams a day), but it is also created by cells lining the small intestine and by individual cells in the body.

• When your doctor takes a blood test to measure your cholesterol level, the doctor is actually measuring the amount of circulating cholesterol in your blood, or your blood cholesterol level.

• About 85 percent of your blood cholesterol level is endogenous , which means it is produced by your body. The other 15 percent or so comes from an external source -- your diet.

• Your dietary cholesterol originates from meat, poultry, fish, seafood and dairy products. It's possible for some people to eat foods high in cholesterol and still have low blood cholesterol levels. Likewise, it's possible to eat foods low in cholesterol and have a high blood cholesterol level.

This coronary artery is becoming dangerously blocked as the cholesterol builds up.

Structure of cholesterol

123

45 6

78

910

1112

1314 15

1617

H O

20 22

23

24

25

26 27

18

19

21

Phytosterols (dari tanaman)

123

45

678

910

1112

13

14 1516

17

HO

2022

23

24

18

19

21

123

45

678

910

1112

13

14 1516

17

HO

2022

23

24

18

19

21

Stigmasterol Glusterol

steroid

vitamin E (tocopherol) • As an anti-oxidant that assists in protecting cellular and

subcellular membranes in the body.• Helping the body's immune system. • May slow down premature aging by way of its protective

effects from free radicals caused by environmental factors. • May prevent cancer growth.• May lower blood sugar levels in diabetic patients• Inhibits platelet formation that are associated with

atherosclerosis.Only a relatively small amount of vitamin E is required to meet normal daily requirements. Fortunately, this amount is easily obtained from foods such as oill, many grains, nuts, and fruits, as well as fatty parts of meats.

5. Biomembrane

It must keep its molecules of life ( DNA , RNA , and its assortment of proteins ) from dissipating away.

It must keep out foreign molecules that damage or destroy the cells components and molecules.

Composition of biomembrane

Lipids phospholipids cholesterol Glycosphingolipids

Protein intrinsic protein extrinsic protein

Others saccharide and ions

Biological membranesCARBOHYDRATEEXTERIOR OF CELL

LIPID BILAYERPERIPHERAL PROTEIN

INTEGRAL PROTEIN

CYTOPLASM SIDE

The Fluid Mosaic Model

Lipid bilayers are fluid, and individual phospholipids diffuse rapidly throughout the two dimensional surface of the membrane; Membrane proteins diffuse throughout the membrane in the same fashion.

To "flip-flop" through the membrane to the opposite side is uncommon. To do so required the hydrophilic head of the phospholipid to pass fully through the highly hydrophobic interior of the membrane, and for the hydrophobic tails to be exposed to the aqueous environment.

The Fluid Mosaic Model

旋转侧向移动摆动 翻转

Factors Influencing Fluidity of Biological Membrane

the ratio of saturated to unsaturated hydrocarbon chains of the phospholipids;level of cholesterol in the cell membrane;Other factors such as ionic strength, polar group of phospholipids.

Membrane Transport Mechanisms

Simple Diffusion Diffusion is always down a concentration gradient. Facilitated DiffusionActive Transport Active transport requires the expenditure of energy.

The Na+-glucose Co-transporting Mechanism

Na+-K+-ATP酶

Epithelial Cells are Joined Together