BIOL 100 Lecture Notes - Lecture 6: Tonicity, Osmoregulation, Osmosis
Document Summary
Membranes are fluid mosaics of lipids and proteins. Selectively permeable: allows some substances to cross more easily than others. Molecules move across membrane down its concentration gradient. Move from high concentration to low concentration. Movement from o2 (from outside to inside) to co2 (from inside of cell to outside) - breathing: osmosis. Diffusion of water across a selectively permeable membrane down its concentration gradient. Water always has substances dissolved in it. Tonicity: ability of solution causing cells to gain or lose water. Depends on concentration of solutes in the solution relative: types of solution affecting tonicity. Hypotonic: solute concentration lower than cell water inside cell. Hypertonic: solute concentration higher than cell water outside cell: osmoregulation. Plants and animals prevent too much fluctuation of water for survival. Slightly different between plants and animals: facilitated diffusion. Requires proteins to transport charged/polar molecules across cell. Energy is needed for active transport of solutes.