LIFE 102 Lecture Notes - Lecture 11: Hydrophile, Facilitated Diffusion, Lysis
Document Summary
Passive transport is diffusion through a membrane without energy investment. Result of random movement of individual particles. Diffusion is the spontaneous movement of a substance down a concentration gradient. Example: co2 and o2 as a cell performs cellular respiration. Osmosis is the diffusion of water across a membrane. Isotonic: when the solutes are equal to each other. Most terrestrial animals have extracellular fluids that is isotonic to their cells. Still have to use transport to counteract slow leakage ions, maintain isotonicity. Seawater is isotonic to many marine invertebrates- doesn"t mean all their ion concentrations are identical to seawater! Paramecium caudatum lives in pond water, which is hypotonic to the cell. Plant cells, fungi, prokaryotes, and some protists have cell walls. Cell walls can"t prevent excessive loss of water. Remember the structure of the membrane (hydrophobic layer) Difficult for them to pass through the non-polar layer. Still have a hard time moving through.
