Lipids and Lipoproteins PDF

LIPIDS AND Chapter 8 LIPOPROTEINS  PREAMBLE PowerPoints are a general overview and are provided to help students take notes over the video lecture ONLY. PowerPoints DO NOT cover the details needed for the Unit exam Each st...

LIPIDS AND Chapter 8 LIPOPROTEINS  PREAMBLE PowerPoints are a general overview and are provided to help students take notes over the video lecture ONLY. PowerPoints DO NOT cover the details needed for the Unit exam Each student is responsible for READING the TEXTBOOK for details to answer the UNIT OBJECTIVES Unit Objectives are your study guide (not this PowerPoint) Test questions cover the details of UNIT OBJECTIVES found only in your Textbook!  INTRODUCTION AND CLASSIFICATIONS Lipids Class of organic compounds which are actually or potentially esters of fatty acids. Soluble in organic solvents and nearly insoluble in water, because they are very hydrophobic Major lipids are cholesterol, triglycerides, phospholipids, and glycolipids. Lipids are classified into five classes: Sterol derivatives Fatty acids Glycerol esters Sphingosine derivatives Terpenes  CLASSIFICATION OF CLINICALLY IMPORTANT LIPIDS (1) Cholesterol and cholesteryl esters Sterol Steroid hormones derivatives Bile acids Vitamin D Short chain (2-4 C atoms) Medium chain (6-10 C atoms) Fatty acids Long chain (12-26 C atoms) Prostaglandins Glycerol Triglycerides esters Phospholipids Sphingosine Sphingomyelin derivatives Glycosphingolipids Vitamin A Terpenes Vitamin E Vitamin K  CLASSIFICATION AND BIOCHEMISTRY OF LIPIDS (2) Cholesterol Found exclusively in animals and humans, where it is the primary sterol derivative. Contains 27 carbon atoms and four fused rings (A, B, C, and D) called the perhydrocyclopentanophenanthrene nucleus.  CLASSIFICATION AND BIOCHEMISTRY OF LIPIDS (3) Cholesterol Exogenous cholesterol Absorbed in the diet, bile, intestinal secretions, and cells Endogenous cholesterol Produced by the liver Made from simpler molecules, particularly acetate. Absorption Cholesterol is solubilized by the formation of mixed micelles. Micelles are important not only in solubilizing cholesterol but also in facilitating its transport to the intestinal luminal cell wall, where it is absorbed. Maximum absorption of lipids and cholesterol occurs in the middle and terminal ileum of the small intestine.  CLASSIFICATION AND BIOCHEMISTRY OF LIPIDS (4) Cholesterol Synthesis and Catabolism Once cholesterol is synthesized, it is released into circulation in complexes called lipoproteins. Very-low-density lipoproteins (VLDLs) Cholesterol reaching the liver is either secreted unchanged into the bile or metabolized to form bile acids.  CLASSIFICATION AND BIOCHEMISTRY OF LIPIDS (5) Fatty Acids Simplest form of lipids with the chemical formula RCOOH. R stands for an alkyl group with a straight chain of an even number of carbon atoms. Saturated fatty acids contain an alkyl chain without a double bond between C atoms. Classified according to the degree of saturation. Saturated fatty acids Contain an alkyl chain without a double bond between C atoms Monounsaturated fatty acids Contain one double bond Polyunsaturated fatty acids Have more than one double bond  CLASSIFICATION AND BIOCHEMISTRY OF LIPIDS (6) Sphingosine Derivatives Sphingosine Long-chain, monounsaturated amino alcohol. Sphingolipids Structural components of cell membranes Sphingomyelin Important component of the myelin sheath  CLASSIFICATION AND BIOCHEMISTRY OF LIPIDS (7) Prostaglandins Derivatives of fatty acids comprising 20 C atoms, including a five-carbon cyclopentane ring Appear hormone-like in action Synthesized at the site of action and in almost all tissues Short lived with a half-life of seconds  CLASSIFICATION AND BIOCHEMISTRY OF LIPIDS (8) Glycerol Esters One of the common alcohols found in human metabolism. Glycerol is a 3-carbon molecule containing three hydroxyl groups. Triglycerides (TGs) Most common glycerol esters in plasma, composed of glycerol and three fatty acids Comprise 95% of fat stored in tissue From plants, tend to have large amounts of linoleic residues Called polyunsaturated fats From animal sources tend to have predominantly saturated fats  CLASSIFICATION AND BIOCHEMISTRY OF LIPIDS (9) Phospholipids Basically triglycerides with an additional group Hydrogen, choline, and serine Often referred to collectively as lecithins Synthesized in the liver Important part of the outer shell of lipoproteins  LIPOPROTEINS (1) Lipids are transported by means of rather complex micellar structures called lipoproteins, which consist of: An outer layer of proteins Apolipoproteins Polar lipids (phospholipids) Unesterified cholesterol An inner core of neutral lipids (phospholipids and esterified cholesterol).  LIPOPROTEINS (2) Classified into five categories Chylomicrons Very-low-density lipoproteins (VLDL) Intermediate-density lipoproteins (IDL or LDL1) Low-density lipoproteins (LDL) High-density lipoproteins (HDL)  LIPOPROTEIN COMPOSITION, DENSITY, AND FUNCTION Lipoprotein Composition Density (g/mL) Function Chylomicrons Triglycerides: 84%