Week 9 Notes
Week 9 Notes BSC 450
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This 12 page Class Notes was uploaded by Jordana Baraad on Saturday October 24, 2015. The Class Notes belongs to BSC 450 at University of Alabama - Tuscaloosa taught by Dr. Ramonell in Summer 2015. Since its upload, it has received 27 views. For similar materials see Fundamentals of Biochemistry in Biological Sciences at University of Alabama - Tuscaloosa.
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Date Created: 10/24/15
1020 Lipids Fatty Acids are the building blocks Fatty acid combinations of CH2 units 436 carbons carboxylic acid 12 C s lower limit for membrane lipid Deprotonated in biological systems Shortcut name C s double bond 12 0 Double bonds unsaturated No double bonds saturated Monounsaturated Fatty Acid Nomenclature Pic cis 9Octadecanoic acid Shorthand 1810 9 Cis con guration typical Superscript number indicates location of double bond ing starts carboxylic C PUFA Nomenclature Nutritionists only care about terminal double bond Start there then count in quotOmega 3 squot and quotOmega 6 squot General Rules for Fatty Acids 1 Even C s 1218 standard 2 Double bonds not conjugated in animals a Plants can have conjugation lack of mobility l more biochem complexity b Plants radiate off excess energy chlorophyll carotenoids c Monounsaturated FA s d9 most common d Polyunsaturated FA s d12 amp d15 common 3 Double bonds in Cis con guration can be trans predigestion Effect of Structure on Chemical Properties Weak forces at play hydrophobic effect and Van der Waal s Forces Saturated fat nicely packed together Plantsbacteria reorganize membranes More fatty acids with more double bonds Resistance to freezing Decreased danger of membrane rupturing when previously frozen membrane melts quothard freezequot Increased melting point proportional to increased length in Cchain more impact of weak forces C s Melting Point Celsius 12 44 14 54 16 63 18 69 Opposite trend with double bond can t take advantage of weak forces Delta Melting Point Celsius 180 69 181 13 182 2 183 011 FA s have a number of functions 1 Waterproof plants cuticle a Waterproo ng wax layer and defense bad taste andor poisons embedded 2 Spermaceti organ in whales D buoyancy structure goes w function a Change density of whale s body with changing water pressure and temperature as whale descends to deeper depths of ocean and remains there b Valuable oil Slide structure comprises nearly 100 beeswax waterproof durable Tridlvcerides TAGS are Fatty Acid Esters of lecerol Energy storage 1 2x more energy g FA v g sugar EFFICIENT a sugar C s more oxidized 2 nonhydrated downside slower access for E a betaoxidation mitochondria TAGs hydrophobic v sugars which attract water Stored in lipid droplets COMPLETELY exclude water EFFICIENT longterm storage v sugar 1 g sugar w 2 g water add weight Structural Lipids Each lea et has unique properties cytoplasmic lea ets v facingout Amphipathic 2 FA s polar head group Phospholipids Phosphate linker 3rOI position changes PhosphaUdylchoHne ll serine amino acid ll ethanolamine med amino acid inositol pseudo sugar missing an O cleaved from membrane D signaling Common Polar Groups on Phosoholipids Sphingolipids Ceramide simplest head group 1 H Required for neurological structure mutation lethal Sphingomyelin phosphocholine head group Helps conduct electric currents Major sphingolipid Glycolipids Help identify different tissues ie blood typing Galactose underrated glycolipid Sterols 4 ring structures planar substituent steroid hormones are cholesterol derivatives cholesterol important sterol w polar head group and alkyl side chain thsiolodical Role of Sterols Plants have steroid hormones brassinolide test q mammals obtain cholesterol from food or synthesize it de novo in the liver Vitamin A plays a role in vision b and c split in half b night vision adapting to change in levels of light c eye rod an cone sensitive to light cis con guration D trans w ight start of signaling pathway to brain Vitamin D plavs a role in calcium uptake Activated by UV light in 2 steps in skin w1015 min exposure in day Rickets Vitamin D de ciency Elimination by UV activation l Vitamin D forti ed milk Discovered at U Wisconsin Cholecalciferol Vit D3 activated inside the body More costly 1apha25dihydroxyvitamin D3 calcitriol next steps in liver and kidney Vitamin E acts as an antioxidant Interact w free radicals to inactivate them l quenching Mitochondria and chloroplasts more susceptible to oxidation As a result have more than their fair share of Vitamin E ROS Reactive Oxygen Species DANGEROUS Vitamin K plays an important role in blood clotting ESSENTIAL enzyme Activates prothrombin Doesn t need activation until blood clotting necessary c rat poison inhibits reductase treatment massive does of Vitamin K Biological Membranes Membranes are Essential for Life 1 of de ning characteristics of life compartment formation way of separating cellular components double membrane innerouter layer mitochondria nucleus chloroplasts LOTS of communication Previously individual organisms endocytised Mitochondria and chloroplasts stress sensors Signals D nucleus D gene expression Retrograde signaling mitochondria D nucleus Anterograde signaling nucleus D mitochondria chloroplasts Functions of Membranes De nes boundaries allows importexport l select main ions against concentration gradient selective import of nutrients eg lactate selective export of waste eg antibiotics store energy as proton gradient how ATP is synthesized HATPase is membrane protein Retain metabolites ions External signaling transmitting info Levels of 3D Structures for Lipids ln aqueous soln A D C smallest D largest ALL spontaneous formation no energy required a polar head 1 FA tail lowest energy structure thermodynamically favorable b 2 FA tails prevent micelle formation too much steric hindrance weak forces hydrophobic effect amp Van der Waal s lipid majority of structure holds membrane together minor polar head interactions c formed w enough bilayer present folding in on self aqueous core studied for drug delivery need other proteins not formed by chance controlled process Thermodynamics of Membrane Function 1 hydrophobic effect 2 Van der Waal s interactions Minor Hbonding polar head groups Lipid Vesicles Spontaneous vesicle formation Biological Membranes Share Common Properties 1 impermeable to ions a problem charge 2 asymmetric not same composition on both sides a with respect to phospholipids and proteins 3 dynamic constant motion a replacement cycling of phospholipids receptor proteins etc Biological Membranes are impermeable to polar and charged compounds NaKCl ion channel gated or not Against concentration gradient ATP typically required Active transport Water can diffuse through membrane independently SLOW process Special transporters aquaporins H20 molecules line up 1 by 1 passed from one amino acid to the next Upside rapid water transport 1st discovered in plants 4 glucose transporters permeability not based on size charge is IMPORTANT limiting factor water and glucose PASSIVE transport don t require energy shapesize speci city Permeability in terms of Thermodynamics Goal move polar charged compound across border Transporter provides hydrophilic environment across membrane Specialized regions long chain hydrophobic transmembrane domains Extracellular Matrix ECM a No transporters a Desolvation b Breaking all Hbonds c Energy barrier increased highly unfavorable bTransporter a Some favorable interaction w transporter even if not as much as with water b Much more rapidef cient decreased energy barrier lower entropic pena y Cytoplasmic Polar charged compound a resolvation reform favorable interactions The Membrane is Asvmmetric each side of membrane has different phospholipid types Fluid Mosaic Model Fluid lipids Mosaic proteins Dark blue inner light blue outer Phosphatidylserine important in cell death Phosphatidylinositol 4phosphate always inside Involved in cell signaling will be cleaved l motion in cell pathway sphingomyelin almost all out peripheral protein unique distinct lipids skate along surface due to weak forces integral protein single transmembrane helix unique distinct proteins long hydrophobic stretches transmembrane hydrophilic on either side associate with ECM or cytoplasm sugars always outside Membrane Composition is Unique and Related to Function Each member has own pro le Can identify organelle based on pro le Plants chloroplast membrane has extra sugars Cholesterol D uidity Most phosphatidylcholine in Golgi Membranes are Dvnamic due to their NonCovalent Interactions Too much heat D membrane falls apart Balance orderdisorder is KEY Ordered semicrystalline rigid Disordered uid Some stability at higherlower temperature Depends on which lipids present Lipids can move within the membrane 2 basic movement both uncatalyzed 1 transbilayer quot ip op diffusion a VERY slow b Outer ips l inner i Problem polar head through hydrophobic bilayer 2 atera diffusion a lots of movement within single lea et b very fast 1microm sec 1 phospholipid could circe entire bacteria in 1 sec saturated FAs myristic acid palmitic acid unsaturated FA s palmitoleic acid oeic acid Membrane Diffusion Flippases Flippases phospholipid transporters Transmembrane proteins 1 ippase ptype VERY speci c to a particular phospholipid 2 oppase ABC NOT selective binds any phospholipid a ABC ATPBinding Cassette b Eg defective CI transporter responsible for cystic brosis 3 scramblase doesn t require ATP Hop Diffusion Model of Lipid Movement Transition between every color change signi es hop Barrier fence Sphindolipids and Cholesterol can form Lipid Rafts in the Membrane Lipid raft thicker l vesicle formation cavelin important protein for this associate with cholesterol adapter protein l recruit claithrin important for endocytosis quotcaveolaquot cave associate in dimers more caveola come as increased structure formation bottom right AMF image of lipid rafts thicker bc contain cholesterol and sphingolipids Role of Cholesterol in Membrane uidity c L a l a y cm 51quot it 3 g g ski P N 3quot l Sharp in ection point in sigmoidal curve Flat ring structure can t between phospholipids nicely Membrane Curvature and Fusion are involved in many Biological Processes 1St 4 steps secretion vesicle formation important fusion of sperm and egg cell division viral infection membrane receptors endocytosis at point of connection Neurotransmitter Release Step 1 Secretory vesice targeted D plasma membrane All alphahelix Snares V snare amp T snare lots different types combination D speci c target SNAP 25 amp NSF assist with vesicle diffusion in target membranes Neurotransmitter Release Step 3 Curvature zipping l tightening Curvature l hemifusion real contact Neurotransmitter Release Step 4 Complete contact between lipid portions and complete fusion D release pore D Carbon released Important in developmental and defense systems httpsstudysoupcomuniversityofalabama tuscaloosabsc450oneweekof notesweekQnotesid71201
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