HLSC 1200U Lecture Notes - Lecture 3: Facilitated Diffusion, Passive Transport, Cell Membrane
Document Summary
Substances (or water) are moved down a concentration gradient: from high to low. Substances are moved against a concentration gradient: low to high. Substances enter (or leave) cell in a package (vesicle) Simple diffusion: does not require any special channels or carriers. Very specific: only one solute can pass through. Gated channels: open (active) or closed (inactive) Aquaporins: allows h2o to go through cell membrane. Very specific: only one solute can use each type of carrier. Usually reversible: depending on concentration inside + outside cell. Channel-mediated (facilitated) passive transport of water across the membrane. Equilibrium same conc. of stuff on both sides. Water pressure that develops as a result of osmosis. Example: osmotic pressure outside cell relative to osmotic pressure inside cell. What happens to cells: shrivel and shrink. Reason: water moves from cell to surrounding. Hypotonic lower pressure solution: what happens to cell: swells, reason: water moves into cell, effect: lysis, serious damage.
