8_Transport_x_membranes - 8 Transport X Membranes 3...

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} - } Concen potential diff across barrier - } Na/K pump 8 Transport X Membranes 3 categories 1. CELLULAR TRANSPORT Exchange of material between cell and environment (thru PM) Example: Uptake of nutrients Removal of waste Pumping of ions 2. TRANSCELLULAR TRANSPORT Moves material through the cell – in one side, out other Example: Epithelial cells of gut Plant root cells 3. INTRACELLULAR TRANSPORT Transport of material in and out of organelles MECHANISMS OF TRANSPORT: PASSIVE TRANS does NOT requires E diffusion from - conc - conc If molecule small or non-polar can pass directly thru membrane: Glycerol Ethanol Urea CO 2 O 2 H 2 O May often need specialized membrane protein to “facilitate” passage passive trans: G < O (exogonic) ACTIVE TRANPORT Requires E! G > O (endogonic) Net movement - conc - - conc Memb proteins “pumps” create conc gradients xross membranes AT REST: 2/3 of E used by body is to maintain ion gradients x membs Ex: H + , K + , Na + , Ca ++ Charged - charged gradient - elect membrane potential COMBINATION: Charge gradient Concen gradient “electrochemical gradient” Stores - Ep – used to do biological work! (syn atp)
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PASSIVE TRANSPORT – Diffusion occurs both directions “net” movement favored from high conc - cou G = conc P = - G = M Small molec simple diffusion Non polar molec [O 2 , [ O 2 , ET-Oh Ability governed by MEMBRANE PERMEABILITY - det by several factors - 1. Size If small enough can diffuse thru lipids – even if polar! Ex – H
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8_Transport_x_membranes - 8 Transport X Membranes 3...

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