Lipid Chemistry - Conjugated Lipids PDF

Faculty of Medicine Medical Biochemistry & Molecular Biology Lipid Chemistry -Conjugated lipids By: Dr. Doaa T. Elsabagh M.Sc., M.D  Simple Lipids - waxes Esters of fatty acids with higher monohydroxyl alcohols other than glycerol. Th...

Faculty of Medicine Medical Biochemistry & Molecular Biology Lipid Chemistry -Conjugated lipids By: Dr. Doaa T. Elsabagh M.Sc., M.D  Simple Lipids - waxes Esters of fatty acids with higher monohydroxyl alcohols other than glycerol. They are important for the manufacture of lubricants, polishes, ointments and cosmetics. Bee wax contains myricyl alcohol (C30H62O). | 2 | 3 Simple Lipids - waxes | 4  Lipids Chemistry Classification of lipids: ✓ Esters of fatty acids with alcohols ✓ Simple lipids + non lipid part ✓ derived from the simple and conjugated lipids by hydrolysis. | 5  Compound lipids - Phospholipids Definition: a type of conjugated lipids containing phosphate group e.g. phosphatidic acid and sphingolipids. Phospholipids According to backbone Glycerol = glycerophospholipids Sphingosine = sphingophospholipids | 6  Conjugated Lipids -phospholipids Glycerophospholipids = phosphoglycerides Phosphatidic acid (the simplest phosphoglyceride) and is the precursor of the other members of this group. Hydrocarbon chain of the fatty acid | 7  Conjugated Lipids -phospholipids Glycerophospholipids = phosphoglycerides Phosphatidic acid is the precursor of the remaining Glycerophospholipids The phosphate group on PA can be esterified to another compound containing an alcohol group to give a new glyceroPL + serine =phosphatidyl serine + Ethanolamine→ phosphatidylethanolamine (cephalin) + Choline→phosphatidylcholine (lecithin) + Inositol→phosphatidylinositol + Glycerol→phosphatidylglycol | 8  Conjugated Lipids -phospholipids Glycerophospholipids = phosphoglycerides | 9 Phosphatidylglycol  Conjugated Lipids -phospholipids Glycerophospholipids = phosphoglycerides Cardiolipin Two molecules of PA esterified through their phosphate groups to an additional molecule of glycerol is called cardiolipin (diphosphatidylglycerol). | 11 DiPhosphatidylglycol Phosphatidylglycol (cardiolipin)  Conjugated Lipids -phospholipids Glycerophospholipids = phosphoglycerides Cardiolipin Cardiolipin is found in bacteria and eukaryotes. In eukaryotes, cardiolipin is virtually exclusive to the inner mitochondrial membrane, where it appears to be required for the maintenance of certain respiratory complexes of the electron transport chain | 13  Compound lipids - Phospholipids Definition: a type of conjugated lipids containing phosphate group e.g. phosphatidic acid and sphingolipids. Phospholipids According to backbone Glycerol = glycerophospholipids Sphingosine = sphingophospholipids | 15  Conjugated Lipids -phospholipids Sphingolipids = sphingophospholipids Sphingomyelin Amide linkage=COOH +NH2 ceramide=sphingosine +fatty acid sphingomyelin= Ceramide + phosphorylcholine | 16  Conjugated Lipids -phospholipids Sphingolipids = sphingophospholipids The backbone of sphingomyelin is the amino alcohol sphingosine, rather than glycerol. A long-chain fatty acid is attached to the amino group of sphingosine through an amide linkage, producing a ceramide, ceramide is also a precursor of glycolipids. The alcohol group at carbon 1 of sphingosine is esterified to phosphorylcholine, producing sphingomyelin, the only significant sphingophospholipid in humans. Sphingomyelin is an important constituent of the myelin of nerve fibers. | 17  Conjugated Lipids -phospholipids Importance | 18  Compound lipids - Phospholipids Importance ✓ Phospholipids are chemically formed of polar heads (phosphate groups) non-polar tails (long chain fatty acids) ✓ Such criteria of phospholipids enable them to perform important functions as: 1. It enters in the structure of cell membrane. 2. Brain and nerves are rich in sphingomyelin and cephalin. 3. It enters in the structure of lipoproteins that are important in lipid transport. 4. It enters in the structure of lung surfactant. | 19  Conjugated Lipids - Lipoproteins Definition: These are complex lipids formed of lipids (e.g. cholesterol, phospholipids or triglycerides) conjugated with protein (apoliporoteins). | 20  Conjugated Lipids - Lipoproteins Function of Plasma lipoproteins? ✓ convert water insoluble lipids into water soluble complexes. ✓ This facilitates transport of lipids between blood and different tissues. | 21  Conjugated Lipids - Lipoproteins ❑ Basically, they are formed of Hydrophobic core cholesterol esters and triglygerides Hydrophilic coat polar parts of phospholipids, unesterified cholesterol and apoprotein | 22 Conjugated Lipids - Lipoproteins | 23  Type of lipids coat core ✓ Polar heads of PLs ✓ Hydroxyl group of cholesterol ✓ Non polar tails of PLs ✓ Cholesterol ester ✓ TAG ✓ Fat soluble vitamins ✓ Steroid nucleus and hydrocarbon side chain of cholesterol | 25  Conjugated Lipids - Lipoproteins ❑ Components: 1. Chylomicrons 2. Very low density lipoproteins (VLDL, or pre- β- lipoproteins) 3. Low density lipoproteins (LDL or β- lipoproteins) 4. High density lipoproteins (HDL or α-lipoproteins) | 26  Conjugated Lipids - Lipoproteins 1. Chylomicrons Transport exogenous dietary triacylglycerol and cholesterol from intestines to peripheral tissues 2. Very low density lipoproteins (VLDL) Transport of endogenous synthesized triacylglycerol from liver to peripheral tissues. 3. Low density lipoproteins (LDL) Transport of cholesterol to tissues. 4. High density lipoproteins (HDL) Reverse cholesterol transport. It removes accu-mulating cholesterol from peripheral tissues es-pecially blood vessels to liver | 27  Conjugated Lipids - Lipoproteins Lipoproteins and atherosclerosis: a. LDL represents the transport of cholesterol to the tissues while HDL represents the removal of cholesterol from tissues. b. Increased level of LDL is associated with atherosclerosis and coronary heart disease. Increased HDL level in blood represents the protection from atherosclerosis and coronary heart disease. c. Thus, the ratio LDL/HDL is used in prediction of atherosclerosis and coronary heart disease. | 29  Conjugated Lipids - Lipoproteins Mechanism of atherosclerosis: LDL undergoes lipid peroxidation and causes inflammation in the wall of blood vessels. Accumulation of macrophages and inflammatory cells leads to destruction of the blood vessel and formation of atherosclerosis and blood thrombosis | 31