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DIFFUSION AND ACTIVE TRANSPORT By Sir William Harrison Hawk Esquire, PhD WHAT IS DIFFUSION? Diffusion is the movement molecules from an area of high concentration to an area of low concentration. Actually, that would be diffusion MORE ON DIFFUSION: In biology, it refers to the movement of gas and liquid particles at temperatures above absolute zero. Diffusive equilibrium- when the concentrations of diffusing substances in the two compartments becomes equal Diffusion is passive Abiotic Factors Affecting Diffusion Temperature Viscosity (density) Mass of particles Facilitated Diffusion Large and polar molecules cant get across the membrane by simple diffusion (glucose, lipids, amino acids, etc.) they are transported across the membrane by channel proteins and carrier proteins Still passive, ALWAYS goes with concentration gradient Osmosis Osmosis is the diffusion of water across a semipermeable membrane. Water moves from an area of low solute concentration to high solute concentration Aquaporin is an integral protein that speeds up movement of water molcules Osmotic Control Osmosis is vital is maintaining homeostasis Goal is to be isotonic Primary Active Transport Requires ATP Uses Integral protein pumps to move ions and large molecules across the cell membrane Molecules can go with OR against the concentration gradient Secondary Active Transport Energy does not come directly from ATP Instead it comes from the concentration gradient/ movement of sodium ions in primary active transport http://www.youtube.com/watch?v=JGF6ry0SWPs
