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MCDB 310 1st Edition Lecture 11 Outline of Last Lecture I. Structure of RNAII. Nucleic Acid Chemistrya. Denaturation/renaturation of DNAb. Using duplex hybrids in the labc. Mutations in DNAd. Other nucleotide functionsIII. DNA based technology Outline of Current Lecture I. Chapter 10: Lipids II. Storage lipidsIII. Membrane lipidsIV. Non-storage/non-membrane lipidsCurrent LectureI. Chapter 10: Lipidsa. We can label lipids with different kinds of molecules (ie-molecules that turn fat deposits red). b. Lipid droplets don’t need membranes because they are chemically inert storage forms of triglycerides. These lipids are used in the cytoplasm.c. White fat (adipocytes) are hydrophobic and will naturally clump togetherd. Three groups of lipids:i. Storage Lipids:1. Fatty acids and oilsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.2. Built to make them stable (inert) and easy to assemble/disassembleii. Structural Lipids:1. Phospholipids and sterols2. The provide structure, stability, and mobility to membranes iii. Other:1. Cofactors, electron carriers, pigments, hormones, etc2. Each of them have a very specific functione. Structural features of lipids:i. Backbones: either sphingosine or glycerol1. Glycerol has three carbons, can put something on each 2. Sphingosine has two carbons, can put something on eachii. Fatty Acids (R-groups: the things that hang off the backbone)1. They are hydrocarbon chainsiii. Complex rings:1. Cholesterol and derivatives2. Cofactors3. Signaling molecules4. VitaminsII. Storage Lipids: Fatty acid Structurea. Hydrocarbon derivatives (length matters and number of double bonds matters)b. Carboxylic acids with hydrocarbon chains (4-36 carbons)c. May be fully or partly saturated, branched or unbranched (usually linear)d. They may contain three carbon rings and R-groups (usually small, methyl or hydroxyl)e. Biological fatty acids usually do NOT have conjugated double bonds (two double bonds only separated by 1 single bond)f. Usually they are separated by a methylene group (has to do with enzymatic activity)g. Nomenclature: How many carbons? How many double bonds? Where are the double bonds?i. Carbon length with a colon and then the number of double bonds (ie- palmitic acid is 16:0  16 carbons, no double bonds)ii. DO NOT memorize these codes for common lipidsiii. One can also identify where the double bonds are located and put that at the end 1. Example: 20 carbon chain with 2 double bonds between carbons 9and 10 and 12 and 13  20:2(Δ 9,12)2. With only 1 number in the superscript: monounsaturated3. With more than 1 number in the superscript: polyunsaturatediv. The most common fatty acids: 12-24 carbon unbranched chains1. Even number of carbons2. Acetate condensation (acetate has 2 carbons  even numbers)h. Physical Properties:i. The chain is non-polar so fatty acids are generally not water soluble1. Slight solubility in water is due to carboxyl group at the end (deprotonated at physiological pH, normally drawn deprotonated)ii. At room temperature:1. Saturated fatty acids are waxy2. Unsaturated fatty acids are oilyiii. These physical properties are caused by chain length and degree of saturation1. Saturated chains are LINEAR  will line up very nicely2. Unsaturated chains contain BENDS  will not line up quite as well(more space in between lipid tails)i. Fatty Acid Esters of Glycerol (trying to make the carboxyl less reactive)i.Glycerol + 3 fatty acids (acyl chains) (see picture at right) ii. Symmetrical, connected with ester bondsiii. Hydrophobic, very non-polar, only polar piece is the double bond to the oxygen  very inertiv. These serve as the storage forms of metabolic fuelv. Cleaved by Lipases (cut the ester links)vi. Advantages of these Triacylglycerols as fuels:1. Hydrophobic: no need for hydration, saves energy (clump togetherto increase entropy in aqueous solutions)2. Carbon atoms are highly REDUCEDa. They yield more energy than carbohydrates through oxidationb. More oxidation  more energyc. Therefore, these glycerols yield a lot more energy than carbohydrates or proteinsj. Waxes: solids at high temperaturesi. Esters of long chain saturated/unsaturated fatty acids + long chain alcohols (up to 70 or 80 carbons)ii. Very high melting pointsiii. These line up very neatly alongside each other, very stable/hydrophobiciv. Will act as waterproofers for feather, prevent evaporation from holly/poison ivy, polishes and lotions (keep waters from coming out)v. Derived from palm, lanolin, and beeswaxIII. Membrane Lipidsa. Glycerophospholipids: two fatty acids joined to glycerolb. Sphingolipids: one fatty acid + one fatty amine (sphingosine)c. Sterols: rigid core of four fused hydrocarbon ringsd. More general terms:i. Phospholipids: some glycerophospholipids and sphingolipds with a polar head group + fatty acidii. Glycolipids: some sphingolipids with a simple sugar instead of a phosphate (if the sugar is deprotonated, it can add some polar character)e. See table above for identifying different classes of lipidsi. NOTE: this table just shows MOST membrane lipids, but not all. These are the ones that have a backbone (glycerol or sphingosine) and fatty acids/R-groupsii. Number the top carbon position on Glycerol as 1, middle one as 2, bottom one as 3iii. Sphingosine, on its own, is a L-shaped molecule  only has 2 places for fatty acids/R-groups to bind1. Number the binding position on Sphingosine from the bottom up (OPPOSITE OF GLYCEROL)2. Bottom carbon = 1, upper carbon = 2f. Glycerophospholipids (phosphoglycerides)-derivatives of phosphatidic acid (parent molecule)i. General Structure (see above)1. Glycerol backbone (3 carbon binding positions)a. Spot 1: fatty acidb. Spot 2: fatty acidc. Spot 3: phosphate + polar head group (alcohol)2. The bond between the third carbon and the phosphate is a phosphodiester bond3. The polar head group bound to the phosphate group is what gives each of these molecules unique characteristics ii. Remember: structure dictates function1. Add on different polar head groups in order to perform its particular functioniii. Ether Lipids: Phospholipids with fatty acids in ether linkages (see picture below)1. Example: platelet activating factor  causes blood to clot2. Chemically, ether and ester linkages are not that different3. However, about 50% of heart phospholipids are Plasmalogens (ether linkages)4. We


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