PSL301H1 Lecture Notes - Lecture 19: Integral Membrane Protein, Aquaporin 1, Semipermeable Membrane

• School: UTSG
• Department: Physiology
• Course: PSL301H1
• Professor: Christine Wong

Document Summary

Aquaporin: integral membrane protein channel for rapid water movement across membrane: 10 known in humans, rbc has 2 x 10^5 copies of aqp-1 per cell, plasma membrane of pct cells contain 5 different aquaporins. Solutes: particles dissolved in water solution i. e. na, k, glucose. Osmolality: [solutes] in water generating osmotic force: equal in each fluid compartment, but [solutes] differ, i. e. na/cl-/hco3- highest in plasma, interstitium, i. e. k highest in cells, large anions/proteins. Osmotic force: water movement across semi-permeable membrane due to osmotic gradient. Osmotic gradient: different in osmolality in compartments separated by membrane: water moves from compartment with low osmolality to high osmolality. Hypotonic: water in, cell expands: interstitium and plasma separated by leaky water-permeable capillary, leaky exchange epithelium allows movement through gaps between cells. Starling forces: opposing physical forces determining water flux. Albumin: 68 kda protein in plasma, 40 g/l in plasma but low in interstitium: capillaries have limited permeability to albumin.