Membrane Transport

Membrane Transport - Ch Transport through membrane through...

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Ch t 20 Chapter 20 Transport through membrane
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Why do we need transport? To import biological molecules (fuel and building blocks) To export wastes • Transport of building blocks or degradation Transport of building blocks or degradation products between organelles and the cytosol • Regulate the osmotic pressure Regulate the osmotic pressure Regulate the concentration of certain ions • Create gradients of ions across membranes Create gradients of ions across membranes
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Transport across membranes is usually mediated by proteins Membranes have a hydrophobic core Small non-polar substances are able to pass through membranes unassisted The passage of polar or charged molecules is mediated by proteins
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Movement of solutes across a permeable membrane Electrically neutral solutes Electrically charged solutes
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Thermodynamics of the neutral species transport A ( out ) A ( in ) ) A A A (out) (in) G G G = Δ [ ] [ ] ( ) [ ] out A in A A A ln - A ln RT G RT G G + ° + ° = Δ [ ] out in A A A ln = RT G Δ
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