ELEMENTS OF BIOL CHEM
ELEMENTS OF BIOL CHEM BICH 303
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This 27 page Class Notes was uploaded by Ceasar Fritsch on Wednesday October 21, 2015. The Class Notes belongs to BICH 303 at Texas A&M University taught by Timothy Devarenne in Fall. Since its upload, it has received 53 views. For similar materials see /class/225849/bich-303-texas-a-m-university in Biochemistry at Texas A&M University.
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Date Created: 10/21/15
Membranes Membranes a lipid layer that separates components of living organisms cell membrane organelle membrane function to separate functions of and within cells Makeup 1 lipids proteins I H cholesterol lipid I I Cell exterior Hydrophobic ligosucrhuritle i y 0 licllx Vining ilklithium llll il protein Cholesterol MW Womb mm Cytosol Lipids Lipid broadly defined as a naturally occurring molecule that is at best marginally water soluble but readily soluble in organic solvents such as chloroform or acetone fatty acids and their derivatives and substances related biosynthetically or functionally to these compounds Types of lipids fatty acids Two categories triacylglycerols phosphonpids 1 open chain compounds with polar head groups and long 39 waxes nonpolar tails sphingolipids glycolipids sterolslsteroids 2 fusedring compounds Fatty Acids am hi athic Ii id carbox rou oar end h dro hilic P P P y 9 DD V P hydrocarbon chain nonpolar tail hydrophobic even of carbon atomso OH h 042 hydrocarbon chaIn CH3 unbranched Hal7H2 saturated no C C double bon 0mm gt gtHgt Hg CH unsaturated C C quot2ampan double c Rap bonds f 2 double bonds almost always cis x Ltnnldc acid runaknlc add Andlidonic xdd mm Emakstcate 7 Woman trans oleic acid Fatty Acids unsaturations cis double bond puts a kink in the hydrocarbon tai no conjugated double bonds conjugated 5 5 H H H H H nonconjugated 5 5 H H H c c c H H H Notation of carbons of double bonds 1 80 double bond position 1 8 1 A9 cis oleic acid 0 OH Fatty Acids unsaturations Unsaturations reduces melting point of fatty acids Saturated FA s are generally solid at room temperature Number of Melting Point 39 Acid Carbon Atoms Formula C gnsaturated S are liquid at room temperature Laurlc 12 CHECH COZH 44 Myristic 14 CH5CH2 120021 1 58 Pahnitic 16 II 13CHg H2021 1 63 Steam 18 CH3ltCH2gtMCOZH 71 FA s rarely found free in Arachidic 20 CH5CH2 ISCOZH 77 nature a ma smugcm woman Number of Degree of Melting Point Acid Carbon Atoms Unsamration Formula 2 Pulmimlcic In inn A 1H Il IQJZHIHIH 3902H 705 mm H Inner ll ll17IIlI n Linnlvic IN hie AW IHJCHEM1H2HlIH2HZHIH7Z3H 3 llltIlL llit ix 2 39 1Pl3l lltlglH1H 3H H 11 plant FA s l39llllllillit 21 204 quot 39 39 ill3il 24lll K llziiitzllgigtzogll 5n 3919 2005 BlunnlCale Thomson Triacylglycerols triglycerides Triacylglycerols ester linkage of a fatty acid to each OH of glycerol Generally same FA esterified to all three positions on glycerol Not found in membranes but act to store FA s for metabolic energy source H2I H H2 H21 IH ll L 112 11 InI w Glycerol polar lt3 gt gt 3 gt lt nonpolar lt 3 lt gt lt lt gt lt 2 a simple lriacylglycerol Phosphoacylglycerols phospholipids Phosphoacylglycerols ester linkage of 2 fatty acids and one phosphate P04 group to glycerol PO4 can be esterified to additional alcohol containing compound Phosphatidic acid phosphoacylglycerol with no additional group on P04 Phosphatidyl ester phosphoacylglycerol with an additional group on P04 O 0 FA can vary H ll C1 160 and 180 O U Steun39l group ii a ll t i HCOCR2 HiOng7H HHE H H H ng Linnlt yl group O H CHqO P R CHQO P OH I I i O Phosphatidyl ester Phosphatidic acid Phosphoacylglycerols phospholi pids Phosphatidyl esters if 39 ngjH2 NH C70 0 T12 O H 0 1r unzioivioi 1127thsz M quot lepmmlylclmline r L is 0 0 1 0 1H2 2H 1112 00 0 OH OH 0 P 2113 11 0 NIL1 H H 0 H H H H I Phosphoacylglycerols phospholipids Phosphatidyl esters have highly hydrophilic head group have long hydrophobic tails main components lipids in biological membranes H OH Hydrophilic surfaces Hydrophobic tails V Hydrophilic surfaces SteroidsSterols Steroids lipids consisting of a fused ring system 3 six membered rings 1 ve membered ring function mostly as hormones SteroidsSterols Sterols a steroid with a hydrophobic side chain and a hydroxyl group cholesterol is major component of animal plasma membranes cholesterol is precursor for production of steroids sterols not found in prokaryotes Cholesterol plants contain little cholesterol major sterols 5sitosterol and stigmasterol have additional ethyl groups at 024 Ho CDS lZ ergosterol Membranes Membranes separate cells from the external environment separate organelles from rest of cell controls transport of substances in and out of cell have embedded proteins Membrane characteristics are determined by the lipid and protein component of the membrane How are all of these lipids put together to form membrane hydrophobic interactions hydrophobic tails of phospholipids will interact with each other forming a bHayen hydrophobic tails associate inside Dispel water hydrophilic heads on outside 11533 lgtd quot interact With water Membranes Differences between inner and outer layer of lipidbilayer Phospholipids in outer layer are bulkier hydrophilic heads and hydrophobictails more room Phospholipids in inner layer are smaller hydrophilic heads and hydrophobic tails less room i 539 5 Can distinguish inner and Li outer layer experimentally Ekatwa 1 a based on this difference 7 K L S m w mar mi ucyu zima Elmakslcule rThnmsan Membranes Membrane fluidity saturation of FA s in phospholipids amount of cholesterol temperature Unsaturated FA s in phospholipids can not pack as tightly lncreases fluidity Saturated Unsaturated Polar head Hydrocarbon TWO tail double bonds aaaaaaaaaaaaaaaaaaa an Membranes Membrane fluidity cholesterol Cholesterol OH associates with the polar head groups rigid ring structure associates with FA tail stabilizes makes membrane more rigid Membranes Membrane fluidity temperature at low temperatures hydrocarbon tails of phospholipids become highly ordered crystalline solid increase in heat reduces order of membrane becomes liquid crystal surface area increases Tm temperature at which membrane changes from crystalline to liquid crystal thickness decreases cholesterol will decrease mobility of hydrocarbon tails of phospholipids increasing Tm Membranes Phospholipid transition with in the bilayer Lateral movement of phospholipids 3 within same layer rapid F sea ofphospholipids flipflop of phospholipids from one i layerofbilayerto anotherdoes not take place with out enzyme flipase why would this not happen spontaneously Membranes Proteins Associated with membranes 12 4 Integral membrane proteins 7 7 3 peripheral membrane protein Integral membrane proteins actually enter bilayer Peripheral membrane proteins are loosely associated with polar head groups through polar andor electrostatic interactions Membranes Proteins Associated with membranes ochelix or 3sheet of integral membrane proteins associates with hydrophobic phospholipid tails polar peptide backbone in middle of ochelix or 3sheet hydrophobic side chains on outside interact with hydrophobic phospholipid tails NH Extracellular side Membrane anchoring of proteins Palmitic acid 160 bound to Cys HN l sirlr CH2 Myristic acid 140 bound to N 00c9 fEQ5 terminal ALMyrismyimiou S Palmitoylation o a 7n mmmmmmmmmmmmmmmm M Fluidmosaic Model Fluid In order for membrane proteins to function phospholipids must remain fluid liquid crystal composition of FA s on phospholipids saturatedunsaturated chain length amount of cholesterol will change in response to temperature maintain fluidity Mosaic made up of many different compounds proteins phospholipids etc lots of lateral motion of both phospholipids and proteins proteins float in a sea of phospholipids Cell exterior onth lullmp oodkl 0 Transport Across Membranes Passive transport Active transport movement of substance movement of substance against with concentration gradient concentration gradient from high to low from low to high does not require energy requires energy facilitated diffusion carrier protein used to move largepolar molecules through Memb I simple diffusion small uncharged molecules 021 N21 H201 C02 pass directly through memb 39 O O I C conformational change 0 TC 01 ICOND 0 I 39 1 in l A v I 39 i outside cell 0000 inside cell 0 Transport Across Membranes Passive transport is spontaneous AG Membrane outside inside Concentration Cmt Concentration CW 0 O o o O o o o o O O o QZODSEvanksiEaieT39mmson gas constant temp AGRTn c 0U RTIn 3 W RT In 027 RT 130 R always As T move towards negative As T increases As Cm moves toward Com As Cm surpasses Com Transport Across Membranes Facilitated diffusion of glucose into red blood cells Glucose permease GI loose Qgrmease Glucose in blood conc 5 111M Erythrocyte Glucose permease Facilitated diffusion a zone mocksCale 7 quotmmquot Transport Across Membranes in membranes holes How do integral membrane proteins make facilitated transport Location of hydrophobic amino acids Location of hydrophilic amino acids dhelix V I lt 39 I I b39eR quot quotquot vain Transport Across Membranes Active transport movement of substance against concentration gradient from low to high requires energy AG RT In Cm Where does energy come from Cout ATP ADP P RT 39 2 O OUtS39de Ge conformational change 1 RTn45 I RT150 K quot Requires energy insidecell o o 0 o o 39 0 Primary active transport uses hydrolysis of ATP as energy source Transport Across Membranes Active transport sodiumpotassium ion pump Na rlK pump ff 7 Normal condition of cell om Kinside gt Koutside root EMT quot Nainside lt 53outside 1 quotr E39 a l ll an39 LmzL d3 Inside Uses energy from ATP hydrolysis to transport 3 Na from inside cell to outside and 2 K from outside quot Cell to inside 5 a zone Ernukxlcule Thnmsun Transport Across Membranes Active transport bacterial lactose permease galactoside permease Gradients of protons H contain electrochemical potential gradient ie free energy AG AG RT ln Cin Cout Energy In H gradient Is used to RT In 3 transport lactose 7 7 1 L 39Lctnja Secondary active transport quot RT In 043 use of free energy in electrochemical gradient Li39x39j lf ifh39 RT 085 to power active transport Outside 39 i quot Proton l f pump 1 I Inside N 39K Lactose 3 Fuel 0 2m Ewakslcnle r l39nnmscn
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