PSL300H1 Lecture Notes - Lecture 1: Porosome, Tandem Pore Domain Potassium Channel, Semipermeable Membrane
Document Summary
Impermeable to organic anions (proteins) (stays inside the cell) Water-soluble molecules cannot cross without help (ie: with channels) Gases can diffuse across the membrane freely. Polar molecules and ions need the help of proteins (channels or carriers: simple diffusion. Small lipid-soluble molecules and gases (o2,co2,ethanol,urea etc) pass through pores in the membrane (remember, these are not channels) Movement is down the conc gradient (high conc to low conc) The relative rate of diffusion is proportional to the conc gradient. Passive: no energy input req: facilitated diffusion. Molecule diffuse through the membrane with the assistance of a carrier protein. Carrier proteins aid in the movement of polar molecules (sugars, amino acids: the carrier protein has a binding site where the molecule can attach to. The energy comes from the conc gradient. Passive: no energy input req: rmbr: this diffusion harnesses the energy from moving down the conc gradient, active transport.
