AGRC1020 Lecture Notes - Lecture 5: Antiporter, Electrochemical Gradient, Muscle Tissue
30 Jul 2018
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Cell membrane: functions, selective barrier, detect chemical signals, enzymes that catalyse reactions, connections to other cells, anchors cell extracellular matrix. Cell transport: passive, diffusion through lipid bilayer, diffusion through water-filled protein channels, facilitated diffusion, active, primary active transport, secondary active transport, vesicular transport. Diffusion: movement of molecules by random molecular motion, diffusion is good over short distances, polar molecules low permeability, non polar molecules high permeability. Diffusion through water filled protein channels: permeability is not solely dependant on lipid solubility, size also matters, permeability is inversely related to size. If something is small enough and is hydrophilic it will find its way through the protein channels: 2 important characteristics, often selectively permeable, can (cid:271)e open/(cid:272)losed (cid:271)y (cid:858)gates(cid:859, channels without gates are (cid:272)alled (cid:858)ungated(cid:859) Ion channels influence the rate but not the direction of ion flow across a cell membrane: movement is via passive diffusion due to electrochemical gradient.
