Exam Review - Chapter 19

Of one solute is coupled to an exergonic flow of a

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Unformatted text preview: g system of cholesterol than the unsaturated chains o Slightly thicker and more ordered than the neighboring domains Rafts GPI- anchored proteins Caveolin: integral membrane protein with two globular domains connected by a hairpin- shaped hydrophobic domain, which binds the protein to the cytoplasmic leaflet Caveolae: the inward curve casued by the presence of caveolin dimmers Changes of curvature are central to biological membranes o Ability to undergo fusion with other membranes without losing their continuity o Membranous compartments constantly reorganize Fusion of two membranes requires that 1. They recognize each other 2. Surfaces become closely apposed 3. Bilayer structures become locally disrupted Fusion proteins: integral proteins that mediate membrane fusion, bringing about recognition and local distortion of the bilayer Membrane fusion in synapses is regulated by a family of SNARES v- SNARES: SNARES in the cytoplasmic face of the intracellular vesicle t- SNARES: SNARES in the target membrane v- SNARES and t- SNARES bind to each other, zipping up from amino termini and pulls membranes together zipping causes curvature and lateral tension hemifusion: outer leaflets of both membranes come into contact complete fusion creates a fusion pore pore widens and vesicle contents are released integral proteins in the plasma membrane provide points of attachment between cells integrins: surface adhesion proteins that mediate a cell’s interaction with the extracellular matrix and with other cells o carry singlas in both directions across the plasma membrane, integrating information from extracellular and intracellular environments cadherins: involved in surface adhesion and undergo homophilic interactions with identical cadherins in adjacent cell selectins: have extracellular domains that bind specific polysaccharides on the surface of an adjacent cell o – Solute Transport across Membranes Every cell must acquire from its surroundings the raw materials for biosynthesis and energy production o Nonpolar compounds dissolve in lipid bilayer and cross membrane unassisted o Polar compounds require a membrane protein or ionophores to cross membrane Simple diffusion: movement of a solute from high to low concentrations Membrane potential: transmembrane electrical gradient Electrochemical gradient: the two factors that affect solution movement To pass through the bilayer, the solute must give up its interactions with water molecules and then diffuse across bilayer Facilitated diffusion, passive transport: Transporters, permeases: the proteins involved in facilitated diffusion o Bind their substrates with high specificity, catalyze transport, saturable Channels: allow transmembreane movement of ions at rates that are greater than that of transporters o Show some specificity Passive transporters: transporters that facilitiate diffusion down a concentration gradient Active transporters: drive substrates across the membrane against a concentration gradient System is incapa...
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