BIO 1105 Lecture 2: Biology Lab- Diffusion and Osmosis
Document Summary
Random motion: caused by heat, passively moves molecules in biological systems. We can see small particles move after they collide with moving molecules. Brownian movement: robert browning 1827 first originally described random motion as he observed dead pollen grains in water and viewed them with a microscope. The pollen grains were being jostled by collisions from water molecules. Diffusion: the passive, directional movement of molecules; spontaneous, no energy required. Direction of diffusion depends on the presence of a gradient of concentration, heat, and pressure (high to low). Differentially permeable: membranes that allow some molecules to pass while retarding other. Depends on the solute s size, charge (ions), polarity and lipid solubility. Polar molecules: positively charged areas and negatively charged areas. Nonpolar molecules: have no local area of charge. Dialysis tubing: bag used to model differentially permeable membrane. Do not discriminate between charge and solubility, only based on molecular size.
