BIOL 031 Lecture Notes - Lecture 8: Aquaporin, Glucose Transporter, Paracellular Transport

• School: College of The Sequoias
• Department: Biology (BIOL)
• Course: BIOL 031
• Professor: carey

Document Summary

Key mechanisms for transport of sodium, chloride, water, bicarbonate, glucose and organic anions/cations. Na+ gradient established by the na/k-atpase that favors movement of sodium ions from the lumen to the interstitium. This sets up both a na+ gradient as well as a charge gradient that drives the rest of the exchangers. 1 sodium out for every 3 bicarbonates out because of the charge gradient set up by the na/k-atpase. Paracellular na+ movement from the lumen to the interstitium. Cellular reabsorption is mediated by the cl-/formate- exchange on the apical membrane. Cellular formate anions are exchanged for luminal chloride ions. Basolateral cl- exit is mediated by a kcl cotransporter. Paracellular pathway is highly permeable to cl-, and a favorable gradient exists for passive transport from the lumen to the interstitium. Cellular transport occurs via a high density of constitutively active water channels (aquaporins) on both the apical and basolateral membranes.