PSL300H1 Lecture Notes - Lecture 13: Lipid Bilayer, Membrane Transport Protein, Atp Hydrolysis

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14 Dec 2016
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Cell membrane: permeability, channels, exocytosis, equilibrium potential / resting mp. Cell membrane is not an inert bag holding the cell together - it is composed of phospholipid bilayer. Permeability depends on molecular size, lipid solubility, and charge. So the membrane is said to be selectively permeable. If substance can ross membrane by any means, membrane is permeable to that substance. Small, lipid-soluble molecules and gases (o2, co2, ethanol, urea) pass either directly through phospholipid bilayer or through pores (holes in the membrane) This moves through brownian motion - we don"t understand completely how this works. Movement of substrate is down its concentration gradient (high to low) Relative rate of diffusion is roughly proportional to the concentration gradient across the membrane. The greater the gradient, the faster the rate. Passive: no energy input required from atp - no energy from anywhere else either. Like simple diffusion bc things move along the concentration gradient - no energy (passive)

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