BMB 462 1st Edition Lecture 1 Outline of Current Lecture I. Definition of a lipida. Defining characteristicb. Comparison to other monomersII. Fatty Acids: Effect of fatty acid structure on functiona.Trends in changes of fatty acid structureb.Using structure to predict propertiesc.Naming Fatty AcidsIII. Triacylglycerols: characteristic featuresa. Properties and functionsCurrent LectureConcepts to remember (from previous courses): Amino acid structures, Van der Waals interactions, organic chemistry structures (i.e. Hydrocarbons, carboxylates, ester bonds).1. Lipids:a. Definition – Cellular molecules that are soluble in organic solvents, but not soluble in water.b. Comparison - Unlike other monomers, lipids do not have a common structural characteristic. The inability to dissolve in water is used to classify molecules as lipids. (Proteins/amino acids have a central C, a C group, a N group, and a R group; Carbohydrates contain repeating CH2O units; Nucleotides contain a sugar-phosphate backbone and a base.i. Lipids are not true polymers, since they do not have a repeating structuralunit found in all lipids.c. Variety in lipid structure results in variety in functioni. Types of lipids: Fatty Acids, Triglycerols, Steroids, Sphingolipids, Isoprenoids2. Fatty Acidsa. Fatty acids are composed of a polar (hydrophilic) head group and a nonpolar (hydrophobic) tail. These 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.i. Fatty acids are typically 12-24 links long, though longer fatty acids do exist(they are biologically relevant, but very rare)ii. The Polar head is bigger than the nonpolar tail, creating a conical shape. When free fatty acids are thrown in aqueous solution, this conical shape cause the molecules to form a micelle (a round cluster of fatty acids that create a hydrophobic interior surrounded by a single polar membrane barrier between the hydrophobic area and the aqueous solution). b. Adding Carbons to the tail of fatty acids and increasing the degree of unsaturation have big impacts on fatty acid propertiesi. If you add carbons to a fatty acid, the melting point increases; more Van der Waals interactions require more energy to break the fatty acids apart.ii. Adding more cis double bonds (increasing the degree of unsaturation) lowers the melting point; more double bonds result in more kinks in the hydrophobic tail, which makes it more difficult for fatty acids to pack in tight (this is what causes membranes, such as those in olive oil, to remain liquid at lower temperatures).1. Almost all double bonds are cis. Some molecules, such as synthetically manufactured ones, contain trans double bonds. These do not cause a kink in the tail like cis bonds do, but they are very rare and bad for health when consumed.iii. Adding or removing a double bond has a larger affect on fatty acid melting point than adding or removing carbons.c. Naming fatty acids:i. Common names – there is no real pattern to this; common names for fatty acid structures must be memorizedii. Shorthand carbon skeletons – The first number is the total number of Carbon atoms in the molecule. The second number is the number of double bonds. When double bonds are present, their location is noted by listing the first carbon of the bond in parentheses after the Carbon skeleton name.1. i.e. 16:1 (Δ9) – There are 16 carbons and a single double bond which can be found at the 9 carbona. When there is only 1 double bond in a molecule, it is typically found at the 9 carbon.iii. Systematic names – This type of naming uses Latin terms denoting the number of carbons and the number of double bonds, similar to the Shorthand Carbon Skeleton naming. The first part of the name relates to the number of carbons, the second part to the number of double bonds, and the suffix refers to the type of molecule.1. i.e. Eicosapentaenoate. Eicosa = 20 atoms, penta = 5 (double bonds), enoate – an ester of enoic acid. This molecule is an ester with 20 atoms and 5 double bonds.iv. Omega fatty acids – The omega carbon is located in the methyl group at the opposite end of the fatty acid as the carboxyl group. Numbering in this fashion, the number given is the one at which the first double bond appears.1. i.e. in an Omega-3 fatty acid, the first double bond will be found on the 3 carbon, counting 3 in from the end of the tail opposite the polar head group.d. Triacylglycerols – Contain a glycerol back bone and 3 fatty acids (acyl = fatty acid, so triacyl indicates 3 fatty acids)i. The fatty acids are typically 3 different molecules, though on occasion, a triacylglycerol contains 3 of the same fatty acid.ii. Triacylglycerol properties – they are the most abundant type of lipid in the body1. Hydrophobic2. Lighter than wateriii. Triacylglycerols are typically energy storage molecules (they are not foundin membranes)1. Triacylglycerol have ~3 months of energy storage (compared to 24 hours energy stored in glycogen molecules)2. Their light weight and inability to associate with water makes triacylglycerols ideal storage molecules; it is much lighter to store triacylglycerol in the body than to store an energy-equivalent amount of
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