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BIO130 Exam Notes.docx

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Gillian Rowe

Membrane Structure Glycolipids Cytoplasm -sugar group & lipid molecule -lipids glycosylated in the lumen of golgi -in cell, outside of nucleus , fluids and organelles -mainly in outer leaflet, not in inner Cytosol -aq. Part of cytoplasm, non-membrane bound -in some organelles organelles -protects cell in harsh envirments Lumen -inside of organelles 2)membrane proteins -suspended un layer Membrane -mobile in layer -compartments: specific environments -specific functions -scaffold for biomechanical activities -selective barrier -asosociated with bilayer in different ways -transporting solutes(channels) -eg. Receptors influenced by outside -respond to extracellular conditions channels for transport -interactions between cells Membrane Fluidity -rigid at low temeberatures Membrane components 1 membrane, 1 bilayer, two pplpd layers -saturation of pplpds : cis bonds help presernve -no repeating unit patter or patch, no specific fluidity arrangement, everything moves separately -length of pplpd tails: shorter, more fuild b/c less interactions 1) Lipid Bilayer Cytosolic and Exoplasmic Face -Inner outer leaflet -Double membranes: nucleus and mitochondrion, -fluid structure, always moving -amphiphillic, polar head, non polar tail both have intermembrane space -asymertical lipids on either leaflet -lumens of membrane bound organelle faces -certain intracellular signaling proteins need to exoplasmic face bind to specific inner leaflet pplpds -eg, glycolipids found on outer leaflet of plasma membrane but synthesized on lumen face of golgi Phospholipids - polar head, 2 hydrophobic hydrocarbon tails - spontaneously self associate Techniques -artificial bilayers: liposomes: study -Extraction of membrane proteins permeability, study membrane proteins, Detergents monomers: destroys membrane delivery into cells -Properties of integral membrane proteins Addition of phospholipdis to isolated proteins, -most abundant removal of detergents and creation of minicells -tails:14-14 carbons, saturated or -FRAP: Fluorescence Recovery After unsaturated(Kinks, cis double bond) -diffuses laterally, rarely flipflops (only with Photobleaching help of pplpd translacator) Protein fuse with GFP, bleach small area with Pplpd Translocators laser, measure recovery rate, shorter time: -shifts pplpds to non cytosolic leaflet more diffusion -phospholipids are made from cytosolic leaflet on Mobility of Membrane Proteins ER, proteins flips it to lumen side -prevent single leaflet growth -diff protein diff rate: some super limited -limitations of FRAP: only measure population of Steroids proteins no individual -animals: cholesterol, plants: plant steroids -using single molc tracking: found that proteins restricted to domains, something inside cell -1:1 Ratio od cholesterols and pplpds anchors it to a domain -decreased mobility of pplpd tails: less permeable membrane Membrane Transport of Small Molcs Na+, Glucose Symporter (Apical) Lipid Bilayer -NA down gradient, Glucose against -move glucose from lumen into concentrated cell -permeable to hydrophobic molecules, small Glut Uniporter (basolateral) uncharged molecules -impermeable to larger macromolecules, ions -passive transport of glucose from cell to blood stream down concentraton gradient Simple Diffusion Na/K+ P-type Pump (basolateral) -high concentration to low concentration -moves Na+ out of cell to maintain gradient for glucose /Na+ symporter -more hydrophobic , faster diffusion Tight Junctions -maintain asymmetrical dist. Of proteins Membrane Transport Proteins -multipass proteins -different cell, diff transport proteins -each is selective to cargo, some transports one type some transports a range Resting Membrane Potential -ouside (+), inside (-) -K+ leak channel: outwards flow (major) -Na/K pump: 10% of charge, 3NA out, 2 K in: net -1 inside eqm resting potential typically -20-120mv 1)electrochemical gradient without membrane potential -moves down gradient 2)electrochemical gradient with membrane negative inside -transporting positive ion, additive force of electrostatic forces and down gradient 3)electrochemical gradient with positive inside -electrostatic forces work against electrochemical gradient of positively charged ion -ion transports at a slower rate Glucose Transfer from Intestine to Blood Intracellular Compartments and Estrogen Receptor Protein Sorting -regulator of transcription Organelle: subcellular compartment or large -remains in cytosol except when estradiol present macromolecular complex, distinct structure, composition and function in cell; it binds to receptor -activates it, it enters NPCs, binds to enhancer and activates transcription of target gene Endomembrane system -Endosomes Golgi Apparatus -peroxisomes
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