LIPIDS by Endang Astuti Chemistry Department Lipids can

LIPIDS by Endang Astuti Chemistry 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: Triglyserides Phospholipids steroids

Lipid functions 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.

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.

Stearic acid üFatty acids are long unbranched Oleic acid chains of carbon atoms. üA carboxyl (-COOH) group at one end gives the molecule its acidic properties. üMost 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.

COMMON BIOLOGICAL SATURATED FATTY ACIDS Symbol common name 12: 0 Lauric acid systematic name dodecanoic acid structure mp(℃) CH 3(CH 2)10 COOH 44. 2 14: 0 Myristic acid tetradecanoic acid CH 3(CH 2)12 COOH 52. 0 16: 0 Palmitic acid Hexadecanoic acid CH 3(CH 2)14 COOH 63. 1 18: 0 Stearic acid CH 3(CH 2)16 COOH 69. 6 CH 3(CH 2)18 COOH 75. 4 20: 0 Octadecanoic acid Arachidic aicd Eicosanoic acid COMMON BIOLOGICAL UNSATURATED FATTY ACIDS Symbol 16: 1 D 9 18: 2 D 9, 12 common name systematic name Palmitoleic acid Hexadecenoic acid Oleic acid 9 -Octadecenoic acid Linoleic acid 9, 12 -Octadecadienoic acid structure mp CH 3(CH 2)5 CH=CH-(CH 2)7 COOH -0. 5 CH 3(CH 2)7 CH=CH-(CH 2)7 COOH 13. 4 CH 3(CH 2)4(CH=CHCH 2)2(CH 2)6 COOH -9 18: 3 D 9, 12, 15 a-Linolenic acid 9, 12, 15 -Octadecatrienoic acid. CH 3 CH 2(CH=CHCH 2)3(CH 2)6 COOH -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

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 monoglyceride 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.

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

2. Alcoholysis 3. hydrolysis

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.

Phospho-glycerol Stereospecific numbering phosphatidic acid Phosphoglycerides

Nonglycerol lipids

Sphingolipids Example Sphingomyelin

Glycosphingolipids

4. sterols Cyclopentane Phenanthrene Cyclopentanoperhy dro-phenanthrene

Cholesterol 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: n n 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.

• The formation of cholesterol involves a series of complicated biochemical reactions that begin with the widespread 2 -carbon molecule Acetyl Co. A. • 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. Most of the body's cholesterol is manufactured in the liver.

• 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.

21 18 20 19 2 3 HO 13 14 1 4 11 12 10 5 9 6 17 16 15 22 23 24 8 7 25 26 Structure of cholesterol 27

Phytosterols Stigmasterol (dari tanaman) 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 w It must keep its molecules of life ( DNA , RNA , and its assortment of proteins ) from dissipating away. w It must keep out foreign molecules that damage or destroy the cells components and molecules.

Composition of biomembrane Lipids n n n phospholipids cholesterol Glycosphingolipids Protein n n intrinsic protein extrinsic protein Others n saccharide and ions

Biological membranes EXTERIOR OF CELL LIPID BILAYER CYTOPLASM SIDE CARBOHYDRATE INTEGRAL PROTEIN PERIPHERAL PROTEIN

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.

The Fluid Mosaic Model 侧向移动 旋转 翻转 摆动 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.

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

The Na+-glucose Co-transporting Mechanism Na+-K+-ATP酶

Epithelial Cells are Joined Together