BIOL 2021 Lecture Notes - Lecture 4: Electrochemical Gradient, Membrane Transport Protein, Lipid Bilayer
9 Feb 2018
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Document Summary
Size of cargo: transport mechanism. ions, small molecule (sugars): transport proteins. From text: lipid bilayer doesn"t allow movement of polar molecules. T move water soluble particles across membrane, transporters and channels are used. Transporters can be active or passive, but channels are always passive. Passive transport: transporters allow solutes to cross the membrane passively (downhill), the concentration gradient (the difference in concentration) is the driving force for the passive transport and determines its direction. If the solute is charged, both its concentration gradient and electrical gradient (the membrane potential) affect its transport (electrochemical gradient). Almost all membranes do have membrane potential, with the inside of the membrane being more negative than the outside. Which favours the inward movement of positive ions and the outward movement of the negative ions. Active transport: movement of some solutes uphill done by transporters, which are coupled to a source of metabolic energy suchs as ion concentration or atp hydrolysis.
