BSCI 207 Lecture Notes - Lecture 11: Osmosis, Phospholipid, Water Potential
29 Sep 2015
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Dimensional analysis: (don"t need to memorize - just a step-wise explanation of how to derive units of d) Flux, j = (molecules/area)/time = (molecules)/(area x time) = molecules/c m2 s. J = (c m4)(molecules/c m2 s)=d(molecules /c m4)(c m4) So units of d are: c m2/ seconds. Permeability determines how well a compound diffuses across a membrane. Polar molecules dissolve in water because they form hydrogen bonds with water molecules. Non-polar molecules group together because they don"t form hydrogen bonds with water. We can measure how fast different types of molecules diffuse through the membrane. Thermodynamically favorable (whether or not a reaction occurs) vs. kinetically favorable (how fast a reaction occurs) Solutes diffuse until equilibrium in concentration on both sides of membrane. 2 solutes act independently - both diffuse until equalized. Size and charge affect permeability and diffusion rate. Large, uncharged polar molecules don"t pass through membrane. Small, uncharged, polar molecules pass through membrane.
