Dr Hawker BCH 3023C 1 21 23 8 REVIEW REVIEW QUESTIONS QUESTIONS CCHAPTER HAPTER 8 1 What is the definition of a lipid and its solubility in water Lipid a hydrocarbon compound Readily soluble in organic solvents such as chloroform or acetone Sparingly soluble in water fats and lipids are typically nonpolar hydrophobic o 2 main groups of lipids Open chain compounds with polar heads and nonpolar tails Ex FA s triacylglycerols sphingolipids phosphoacylglycerols glycolipids Fused ring compounds Ex Steroids cholesterol 2 What is the structure of a fatty acid Fig 8 1 Define amphipathic Hydrocarbon chain at the nonpolar tail and Carboxyl group at the Polar end It is Amphipathic because FA s are both hydrophobic and hydrophilic Usually contains even of C s Hydrocarbon tail is usually unbranched 3 What is the difference between saturated and unsaturated fat Know how to name fatty acids see Tables 8 1 8 2 o Saturated Only single bonds in the chain trans form o Unsaturated carbon carbon double bonds in the chain cis form kink in chain FA notation 18 1 means there are 18 carbons and 1 double bond Note in the unsaturated FA s besides arachidonic acid there is a double bond at the 9th carbon starting from the carboxyl end 4 Which class of fat fatty acid has a lower melting point Unsaturated FA s have lower melting points than saturated FA s o Plant oil ex Vegetable oil is liquid at Room temp because it has more unsaturated FA s than animal fats solids o Saturated Less carbons Lower melting point Unsaturated Greater the degree of unsaturation lower melting point 5 Be able to draw the structure of a triacylglycerol Fig 8 2 AKA Triglyceride an ester of glycerol with three fatty acids 1 Dr Hawker BCH 3023C 1 21 23 Glycerol polar has 3 OH s that bond with 3 similar or 3 different fatty acids nonpolar to form the same TG o Do not occur in membranes such as phospholipids but they do occur in adipose tissue fat cells and provide means to store fatty acids storage for metabolic E o Saponification how soaps are formed Reaction of boiling triglycerides animal fats or vegetable oils with NaOH form water insoluble salts when used in water containing Ca2 Mg2 and Fe3 ions hard water Acids bases as catalysts products are glycerol and sodium or potassium salts of the fatty acids that react with Ca and Mg to form precipate scum Glycerol used for lotions creams or nitroglycerin 6 Draw the structure of phosphatidic acid Fig 8 4 Phosphoacylglycerol found in plant and animal membranes when the OH of glycerol is replaced or esterified with phosphoric acid rather than by carboxylic acid COOH as they do in TG s When two fatty acids are also esterified to the glycerol molecule the compound is called a Phosphatidic Acid 2 Dr Hawker BCH 3023C 1 21 23 R1 and R2 are the Fatty Acid side chains attached to glycerol monoprotic only one carboxyl group forming an ester bond Phosphoric acid is Triprotic can form more than one ester linkage One molecule of phosphoric acid can form ester bonds to both glycerol and to some other alcohol creating a Phosphatidyl ester 7 Know and be able to draw the major phosphatidyl esters of living cells Pg 197 Phosphatidyl choline Phosphatidyl serine Phosphatidyl ethanolamine Cardiolipin Phosphatidyl inositol Phosphatidyl glycerol 8 What are sphingolipids Where are they particularly abundant in the body NO glycerol Contains long chain amino alcohol Sphingosine FA and R group o simplest compounds of these are called ceramides linked by amide bonds o ceramides contain 1 fatty acid linked to the amino group of sphingosine o abundant in the nervous system o found in plants and animals 9 Be able to draw the structures of sphingosine and sphingomyelin Fig 8 6 10 What are glycolipids Be able to draw the structure of glucocerebroside Fig 8 7 3 Dr Hawker BCH 3023C 1 21 23 Glycolipids when a carbohydrate is bound to an alcohol group of a lipid by a glycosidic linkage Ceramides parent compounds for glycolipids and the glycosidic bond is formed between the primary alcohol group of the ceramide and a sugar residue The resulting compound is called a cerebroside sugar usually Glucose or Galactose cerebrosides found in nerve and brain cells primarily cell membanes CHO portion is usually very complex glycolipids are often found as markers on cell membranes and play a large role in tissue and organ specificity 11 What are gangliosides What is their base structure see notes Fig 8 8 Gangliosides glycolipids with a complex carbohydrate moiety that contains more than 3 sugars One of them is always sialic acid These are also known as glycosphingolipids because of their negative net charge at a neutral pH Gangliosides are present in large quantities in nerve tissues 12 What is the structure of cholesterol Fig 8 9 What are its functions in the body Do we get it in diet or do our bodies make it o Most important steroid a steroid is a fused ring system consisting of 3 six membered rings and one five membered ring The only hydrophilic group in cholesterol is the hydroxyl group therefore it is mainly highly hydrophobic It is widespread in biological membranes esp in animals however it does not occur in prokaryotic cell membranes o Cholesterol functions in cell membranes it s a precursor for other important steroids and it s a precursor for vitamin D3 o Precursor for Sex hormones testosterone estrogen progesterone o Body makes cholesterol And we get in diet 13 What are the purposes of cell membranes Can cause atherosclerosis Every cell has a cell membrane plasma membrane has protein and lipid components To protect from external environment and transport specific substances in out Also important enzymes are found in membranes 4 Dr Hawker BCH 3023C 1 21 23 Phosphoglycerides are main lipid component of membranes but also contain glycolipids 14 What is the lipid bilayer structure Fig 8 10 What force drives its formation What is a micelle Lipid bilayer structure hydrophobic interior and an ability to control the transport of small molecules and ions Polar head groups are in contact with water and nonpolar tails lie in the interior of the membrane The entire bilayer arrangement is held together by noncovalent interactions The surface of bilayer is polar and contains charged groups The nonpolar hydrocarbon interior consists of saturated and unsaturated chains of FA s and the fused ring system of cholesterol Micelle artificial mini cell can enclose molecule in aqueous interior put phospholipids in water and it forms a micelle 15 What