Derived Lipids PDF

Faculty of Medicine Medical Biochemistry & Molecular Biology Lipid Chemistry - derived lipids By: Dr. Doaa T. Elsabagh M.Sc., M.D  Derived lipids DEFINITION These are substances derived from the simple and conjugated lipids by hydrolysis. CO...

Faculty of Medicine Medical Biochemistry & Molecular Biology Lipid Chemistry - derived lipids By: Dr. Doaa T. Elsabagh M.Sc., M.D  Derived lipids DEFINITION These are substances derived from the simple and conjugated lipids by hydrolysis. COMPONENTS 1. Fatty acids 2. Glycerol. 3. Polycyclic compounds e.g. sterols and steroids. 4. Lipid soluble vitamins: They will be discussed later. | 2  Derived lipids STEROLS AND STEROIDS (CHOLESTEROL) DEFINITION They are compounds that contain a ring (steroid nucleus) which is called cyclopentanoperhydrophenanthrene ring. | 3  Derived lipids TYPES OF STEROIDS AND STEROLS 1. Sterol = alcohol that contains steroid nucleus Cholesterol → animal sterol Ergosterol→ plant sterol 2. Vitamin D group (D2 and D3). STEROIDS 3. Bile salts. 4. Steroid hormones (Male and female sex hormones and adrenocortical hor-mones). | 4  Derived lipids CHOLESTEROL Cholesterol Distribution in Body 1. It is present in every body cell (cell membrane) especially in adrenal cortex, liver, kidneys, brain and nervous tissues. 2. In blood: Cholesterol is present in 2 forms free or esterified (combined with fatty acids). The normal level of blood cholesterol is usually less than 220 mg/dl. Any increase above that level is known as hypercholesterolemia. 3. It is insoluble in water and soluble in fat solvents. 4. It is present only in animals and not in plants. | 5  Derived lipids Functions of Cholesterol 1. It enters in the structure of every animal cell membrane. 2. It is used for synthesis of steroid hormones. 3. It is used for synthesis of bile salts. 4. Synthesis of vitamin D3. Chemical Derivatives of Cholesterol 1. Vitamin D3 2. Steroids hormones 3. Bile salts | 6  Derived lipids Chemical Derivatives of Cholesterol 1. Vitamin D3 It is derived from 7-dehydrocholesterol by UV light. 2. Steroids hormones a. Female sex hormones (estrogen and progesterone). b. Male sex hormones (Testosterone). c. Suprarenal cortical hormones including mineralocorticoids and glucocorti- coids. 3. Bile salts | 7  Derived lipids Formation They are produced from oxidation of cholesterol in the liver and secreted in bile to reach small intestine where it helps lipid absorption. They are reabsorbed from the intestine and secreted again in bile (enterohepatic circulation). | 8  Derived lipids Functions of Bile Salts 1. Emulsification of lipids during digestion. 2. Activation of pancreatic lipase. 3. Help absorption of fat-soluble vitamins. 4. Solubilizing cholesterol in bile and prevent gall stone formation. 5. Choleretic action (stimulate their own secretion). 6. Intestinal antiseptic that prevent putrefaction | 9