Biochemistry Lecture 5 PDF

Biochemistry Compound lipids LECTURE (5) DR. El-Sawy 0  Biochemistry Compound lipids De...

Biochemistry Compound lipids LECTURE (5) DR. El-Sawy 0  Biochemistry Compound lipids Definition : Compounds consist of fatty acids + alcohols + other groups. Phosphoric acids Sugars Sulfate Protein Phospholipids Glycolipids Sulfolipids Lipoproteins Structure  Fatty acids, Alcohol, phosphoric acid ± nitrogenous base. Phosphoglycerides Glycerol  (Glycero-phospholipids) Types Sphingomyelin Sphingol (sphingosine)  (Sphingo-phospholipids) A. Sphingomyelin 1. Sphingosine base. 3. Phosphoric acid. Structure 2. Unsaturated fatty acid. 4. Choline base. Function  Form myelin sheath which is electric insulator. DR. El-Sawy 1  Biochemistry Compound lipids B. Phospho-glycerides Phosphatidic acid Lecithin Cephalin Other name Phosphatidyl choline Phosphatidyl serine or ethanolamine  Glycerol. Phosphatidic acid Phosphatidic acid  2 fatty acid. Structure + +  Phosphoric acid. Choline. serine or ethanolamine.  No nitrogenous base Phospatidyl Inositol Plasmalogens Cardiolipin Other Lipoinositol Diphosphatidyl glycerol name Phosphatedic acid Lecithin or Cephalin but fatty acid Structure + at C1 of glycerol is replaced by 2 Phosphatidic acid + Glycerol Inositol. unsaturated alcohol. DR. El-Sawy 2  Biochemistry Compound lipids Functions : 1. They are amphipathic (hydrophilic part + hydrophobic part ) which help : Formation of lipid bilayer in cell membrane. Help T.G absorption in small intestine (micelle). Help T.G transport in blood (lipoprotein). 2. Phosphatidic acid: intermediate compound in biosynthesis of other phosphoglycerides and triglycerides. 3. Lecithin  is a lipotropic agent that prevent fatty liver. 4. Di-palmitoyl lecithin (DPL) is lung surfactant (prevent lung collapse) : In pre-mature infant the lung alveoli do not secrete lecithin in sufficient amount  lung collapse ( respiratory distress syndrome ). 5. Cephalins: have a role in blood coagulation. 6. Plasmalogens: have a role in blood coagulation. 7. Cardiolipin  major lipid in mitochondrial membrane (Key role in mitochondrial structure and function) 8. Phosphatidyl inositol bisphosphate (PIP2)  2nd messenger for hormones. 9. Membrane phospholipids: provide arachidonic acid for synthesis of prostaglandins, leukotrienes. 10. Sphingomyelins: are abundant in the nervous system in the myelin sheath (act as electrical insulator). DR. El-Sawy 3  Biochemistry Compound lipids Cerberosides Gangliosides 1. Sphingosine base. 2. long chain fatty acid. Types 3. Monosaccharide : 3. Oligosaccharide chain. Galactose (Galacto-cerebrosides) Glucose (Gluco-cerebrosides). 1. Electrical insulator in nervous tissue. Functions 2. Receptors for many hormones & cholera toxin. Structure as cerberosides + sulphate group at C3 of galactose. Functions Present in brain & Nervous tissue. DR. El-Sawy 4  Biochemistry Compound lipids  Compound lipids formed of : Types Lipid part (T.G, cholesterol, phospholipids). Protein part (Apolipoprotein α or β). 1. Structure of cell membrane Functions 2. Lipid transport in blood "lipid are water insoluble so they can't be transported alone, so lipids bind to protein make lipoprotein water soluble & can be transported in blood". Nonpolar core (hydrophobic): 1. Triglycerides (TG). 2. Cholesterol ester (CE). Outer layer (hydrophilic): 1. Free cholesterol. 2. Phospholipids. 3. Apoproteins. DR. El-Sawy 5  Biochemistry Compound lipids Chylomicrons VLDL LDL HDL Mainly TG. Mainly TG. Mainly cholesterol. Mainly proteins & Small amounts of Greater amounts of small amount of phospholipids. Structure cholesterol, proteins cholesterol , proteins proteins , Small amounts of & phospholipids. & phospholipids. phospholipids & TG. cholesterol & TG. Site Small intestine Liver Blood Liver Transport cholesterol from Transport Transport tissues  liver (reverse exogenous lipids Transport cholesterol Function endogenous lipids cholesterol transport) from small intestine from liver tissues. from liver  tissues. Protect against  tissues. atherosclerosis DR. El-Sawy 6  Biochemistry Compound lipids Sphinogolipids Sphingolipid Structure Function Enter in structure of Ceramide Sphingosine + FA sphingolipid Ceramide + Sphingomyelin Electrical insulator phosphoric acid + choline Ceramide + Cerbersoides Electrical insulator Galactose or glucose Cerebersoide + Sulfolipids Electrical insulator Sulphate at C3 of sugar Ceramide + Electrical insulator Gangliosides Oligosaccharide chain +membrane receptors DR. El-Sawy 7