BIO 1030 Lecture Notes - Lecture 12: Semipermeable Membrane, Passive Transport, Facilitated Diffusion
21 Feb 2017
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Document Summary
A lower activation energy makes a reaction easier and faster. 3 ways to enter a cell: passive transport, active transport, bulk transport. Passive transport: no energy required for simple diffusion, molecules move down their concentration gradient until equilibrium is reached, cell does not expend additional energy. Molecules already in motion: some molecules slip between phospholipids, facilitated diffusion. Others use transport protein specific to molecule. Water uses aquaporin: explains faster than expected transport rate. Osmosis: diffusion of water across a semipermeable membrane, net movement of water from beaker (higher water concentration) to tube (lower water concentration, solution inside tube rises until equal concentration of water. Effect of osmosis on cells: isotonic solution. Concentration of water is same on both sides of the membrane. 0. 9% saline isotonic to red blood cells: hypotonic solution. Concentration of water outside greater than inside the cell. Plant cells use this to remain turgid: hypertonic solution. Concentration of water outside cell less than inside cell.
