Chapter 20 Lipids rganic and Biochem
20.1 Introduction Found in living organisms Insoluble in water but Soluble in non-polar substances Example of Lipid Solvent: diethyl ether Polar groups in lipids are Smaller than the non-polar groups Two most Common Roles Energy Storage Cell Membrane bi-layer
1 gram of fat = 9 kcal 1 gram of carbohydrate = 4 kcal Also act as Chemical Messengers Four groups o Fats and Waxes o Complex Lipids o Steroids o Arachidonic acid derivatives
20.2 Structure of Triglycerides Triesters of _Glycerol and long-chain carboxylic acids called fatty acids Animal fats and vegetable oils
The carboxylic acids have the following in common: Almost all Unbranched 10-20 carbon chain Even number of carbons ther than some double bonds and CH they have no other functional groups
Two groups of fatty acids Saturated fatty acids o Have only single bonds o Solids at Room Temp. Unsaturated fatty acids o Have at least 1 double bond o Cis isomers dominate o Liquids at Room Temp.
Saturated Refers to the Chains Not Really the Hydrogens VanderWaal forces weakly pack Structure Double bonds interrupt VanderWaal forces: Interrupt packing
Fatty acid nomenclature o Common names dominate o Example: o Stearic Acid : (18:0) o leic Acid : (18:1) o Linoleic Acid : (18:2) o Linolenic Acid : (18:3) o Table 20.1 (pg 472) # of Carbon s in Chain # of Double bonds in Chain
Triglycerides Glycerol typically is esterified by three different carboxylic acids Example: Palmitate (16:0) lcate (18:1) Stearate (18:0)
20.3 Properties of Fats Animal fats: SLIDS Plant or fish: LIQUIDS ILS Solid fats Saturated fats Vegetable oils Unsaturated fats Table 20.2 (pg 474)
Hydrogenation Add H 2 across the double bond of an unsaturated fat Liquid becomes a solid Modern Butter/Lard Substitutes
Saponification Glycerides can be reacted with a base to form sodium salts (soap) How to Make Soap Fight Club?
Box: 20C Soaps and Detergents Surfactants Hydrophobic Hydrophilic Demo water, oil, soap suspensions Surfactant Video
20.4 Complex Lipids Components of cell membranes Two types: o Phospholipids o Glycolipids
Phospholipids Contain alcohol with: _1-2 Fatty acids and Phospho complex o Glycerophospholipids: Structural Alcohol is glycerol o Sphingolipids: Sphingosine instead of Glycerol
Glycolipids Sphingosine with a carbohydrate and Fatty Acid
20.5 Membranes Formed by complex lipids Unsaturated fatty acids are important components Purpose is to separate cells from the external environment and to provide transport for nutrients and waste products
Lipid bilayers Two rows of complex lipid molecules arranged tail to tail Hydrophobic tales point toward each other leaving the Hydrophilic heads projecting to the inner and outer surfaces of the membrane IMPRTANT substances must be able to transport or cross the membrane
Cell Membrane/Lipid Animations tutorial
20.6 Glycerophospholipids Also called phosphoglycerides Structure is similar to simple fats Primary component of Cell Membrane Alcohol is glycerol 2 H groups esterified by fatty acids 3 rd H esterified by a phosphate group which is esterified to another alcohol group (Choline) Three important examples Phosphatidylcholines (Lecithin) Cephalins phosphatidylethanolamine & phosphatidylserine Phosphatidyl inositols (PI)
Phosphatidylcholines Common Name: Lecithin (Page 479) Draw the Molecule and ID the Polar/Non-Polar portions H 2 C C Stearic acid HC C Linolenic acid H 2 C H 2 C C P - Stearic acid CH 2 CH 2 N + Choline - HC C Linolenic acid H 3 C N + CH 2 CH 2 P
Cephalins Similar to Lecithin ethanolamine and/or serine substituted for choline Page 480: H 2 C C Stearic acid - HC C Linolenic acid + H 3 N CH 2 CH 2 P - H 2 C C Stearic acid C HC CH 2 - P HC C Linolenic acid NH 3 +
Phosphatidyl inositols (PI) Important to biological membranes as signaling molecules Page 480 H 2 C C Stearic acid HC C Linolenic acid H 2 C P R H H H H H H H H H H H PI (1 phosphate group) Can have more phosphate groups attached (PIP 2 )
20.7 Sphingolipids Coating of nerve axons ( myelin ) Alcohol is sphingosine NH 2 group connected to fatty acid with an Amide bond H group esterified by phosphorylcholine Ceramide : Fatty acid/sphingosine combination
Glycerol Lipids vs. Sphingosine Lipids How many bonding sites are found on Glycerol? Look up Sphingosine on page 480. How many bonding sites are found on Sphingosine? H 3 C CH CH H HC CH 2 H NH 2
Draw a Sphingolipid (Sphingomyelin)that has a Fatty acid bonded to Sphingosine s #1 bonding site and a phosphate-choline complex bonded to bonding site #2 (look at page 481 for help) ID the Polar/Non-Polar portions of the molecule Does this molecule look similar to a Glycerophospholipid?
Multiple Sclerosis: Nerve axons are protected by myelin sheath MS results in the gradual degradation of the myelin sheath. Nerve axons short circuit Symptoms: Lack of coordination Muscle weariness Loss of vision
20.8 Glycolipids Contain a carbohydrate ne important Example: Cerbrosides H H H H H H HN H H H H 1 Fatty acid (only example with a 24 C) Brain Lipid
20.9 Steroids 3 rd class of lipids Contain the following ring structure: Label parts (Page 483) There may be double bonds and other components
Cholesterol Most abundant steroid in the body Serves as a membrane component in red blood cells and myelinated nerve cells Serves as a raw material for _ther Steroids_
Cholesterol Exists in: Free Form: H Esterified with fatty acid Form: R
Cholesterol is gained 2 ways Ingested in diet Manufactured in Liver Cholesterol is transported throughout the body via Lipoproteins Read Page 487.
HDL: High Density Lipoprotein 50% Protein content - 18% Cholesterol Important for transfer of cholesterol to Liver Good Cholesterol LDL: Low Density Lipoprotein 25% Protein content - 45% Cholesterol Important for cholesterol metabolism (carries cholesterol to cells) Coated Pits LDL Receptor sites Bad Cholesterol if a lack of LDL receptor sites exist.
20.10 Steroid Hormones Cholesterol is the raw material for the synthesis of steroid hormones Fig. 20.6 (pg 488) Progesterone is the primary steroid hormone that all others come from 2 major groups of Steroid Hormones Adrenocorticoids Sex Hormones
H 3 C C H 3 C H Cholesterol Progesterone H H C H 2 CH C 3 H H H C H 2 CH C H Testosterone Cortisol Aldosterone Adrenocorticoid Hormones
Adrenocorticoids Products of adrenal glands Two groups: Mineralocorticoids Regulate the concentration of ions (Na + and K + ) Aldosterone: controls re-absorption of ions Glucocorticoids Regulate glucose and glycogen levels in body Cortisol and Cortisone also act as anti-inflammatories Synthetic corticoid: Prednisolone - used to treat inflammatory diseases (arthritis, asthma, crohn s)
H C H 2 C H H C H 2 C H H Cortisol Cortisone
Sex Hormones Testosterone Most important male sex hormone Not only produced by males Balance of Testosterone to progesterone/estradiol determines sexual differentiation Synthesized from cholesterol Estradiol Synthesized from Testosterone With progesterone regulates menstrual cycle
Conversion of steroids: Testosterone Estradiol Loss of H & Keto-enol tautomerism Draw Testosterone & Estradiol H H H Testosterone Estradiol
20.11 Bile Salts Products of the oxidation of cholesterol Produced in the LIVER Stored in the Gall Bladder Powerful detergents Disperse dietary lipids in the small intestine Forms an emulsion with lipids Removes excess cholesterol Form clumps_ Functions: _Emulsify lipids for digestion _neutralize stomach acid
Show Figure pg 493 H 3 C H - NH H 3 C H NH H H H H S + - - If too much cholesterol is present with the bile salts in the gall bladder Gallstones can form.
Fourth Group: Arachiodonic Acid Lipids Prostaglandins Mediate hormonal actions Cause inflammation and swelling Thomboxanes Causes blood to clot Leukotrienes Responsible for muscle contractions (Non-conscious muscles especially) Mediates hormone action Lungs? Increased levels cause Asthma All come from the precursor Arachiodonic Acid
Aspirin inhibits an enzyme in the conversion reactions of Arachiodonic acid. Aspirin lowers levels of the first 2 lipids Anti-inflammatory Thins blood