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Final

Biochemistry 2580 Final review.pdf

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Department
Biochemistry
Course
BIOC 2580
Professor
Enoka Wijekoon
Semester
Fall

Description
Biochemistry 2580 Final review Lipids structurally diverse group of molecules not defined by their chemical structure but bu their common chemical property HYDROPHOBICITY dissolve in organic solvents 21 chloroformmethanol Function energy storage ex Fats oils triglycerides structural elements of biological membranes ex Phospholipids and sterols signal transduction cellcell communication ex Steroid hormones prostaglandins enzyme cofactors coenzyme Q mitochondrial ETC vitamins A D E K light absorbing pigments ex carotene passive large quantities active smaller quantities Lipids can occur covalently linked to other classes of biomolecules glycolipids sphingolipids gangliosides contain both sugar and lipid portions important constituents of cell membranes ex Blood groups ABO defined by glycolipids displayed on outer surfaces of blood cells lipoproteins VDL LDL HDL plasma lipoproteins associated with cardiovascular health and disease Fatty acids building blocks of many complex lipids central intermediates in metabolism beta oxidation but free fatty acids present in trace quantities carboxylic acids with hydrocarbon chains ranging from 436 carbons most abundant fatty acids in cell have evenof carbon atoms most natural fatty acids are unbranched Lipids aggregate spontaneously to form complexes when dispersed in HO form roughly 2spherical micelles 3few 100nm diameter polar on outside nonpolar inside Saturated fatty acids no double bonds between C in chains laurate 12C Myristate 14C Palmitate 16C Stearate 18C arachidate 20C Unsaturated fatty acids contain 1 or more double bonds between carbons triple bonds not common naturally found in cis configuration kinks chain double bonds in polyunsaturated fatty acids PUFA are methylenebridged not conjugated separated by methylene carbon double single single double conjugated double bond patterns doublesingle double single found in biomolecules but not common in fatty acids Nomenclature 1 assigned to carboxyl carbon andto carbon next to it double bond specified relative to carboxyl carbon by superscriptfollowingSolubility and melting point of saturated fatty acids saturated chain adopt extended conformations and pack fairly orderly extensive favourable interactionsolid at room temp as chain length increases melting point increases and solubility decreases unsaturated fatty acids pack less regularly due to kink caused by cis double bond loweringof favourable interactions less thermal energy required to disrupt disordered packing melting point drastically lowered 1Trans fatty acids partial hydrogenation of unsaturated fatty acids used in manufacturing margarine and similar products isomerize double bonds trans double bonds allow given fatty acids to adopt extended conformation can pack more regularly high melting points believed to have serious negative effects on cardiovascular health O 12 Carboxylic acidalcoholester RCHOCR2 Dehydration reactions O O 12 Carboxylic acidsacidanhydridesRCOCRTryacylglycerols TAGs fats oils acylacid derivative most common form found in nature alcohol group of glycerol forms ester linkage with fatty acid to form TAG Glycerol 3 OH groups major constituent of bulk fats and oils including human depots of fat highly hydrophobic polar carboxylic acids linked in ester which are less polar melting points depend on length and degree of saturation of fatty acids constituents melting point physical state at room temp of natural fats depends on fatty acid composition of constituent TAG most natural fats complex mixtures of simple same fatty acid in each position and mixed 2 or 3 diff fatty acids TAGs higher amount of long chain C16 C18 saturated fatty acids higher melting temp of natural fatPhosphoric Acid HPO is triprotic acid at neutral pH it exists as equilibrium mixture of 342HPO and HPO mixture represented as P inorganic phosphate 3 possible dissociated H 244iphosphorylation adds ve charge to molecules leading to an increase in water solubility phospholipids DNA RNA many proteins phosphoric acid can react with alcohols and acids to form phosphate esters and phospho anhydrides Glycerophospholipids phosphoglycerides primary constituents of biological membranes carbon atoms 12 of glycerol are esterfied to 2 fatty acids while highly polar or charged group rdX is attached through phosphodiester linkage in the 3 Major classes of glycerophospholipids XOH choline ethanolamine serine glycerol ex Phosphoatidylcholine phosphatidylethanolamine phosphatidylserine phosphatidylglycerol major constituents of most membranes Phosphatidylcholine lecithin represents class of lipid rather than single molecule different 12combos of fatty acids at positions R and R correspond to different PC molecules Glycerophospholipids amphipathic hydrophobic tail and hydrophilic head differentiates from TAGs and allows them to make lipid bilayers aggregate into liposomes too bulky for micelles form bilayer that spontaneously folds in to form vesicles or liposomesCarbohydrates most abundant biomolecule monosaccharides single sugar unit oligosaccharides short chains of monosaccharide units disaccharides 2 monosaccaride units2
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