BLG 311 Lecture Notes - Lecture 4: Lipid Bilayer, Membrane Transport Protein, Extracellular Fluid
Document Summary
Cell has hydrophobic interior-> restricts the passage of most polar molecules: this way cells can maintain concentrations of solutes in its cytosol that differ from those in the extracellular fluid. Protein-free lipid bilayers are impermeable to ions. The smaller the molecule and the less strongly its associated with water the more rapidly the molecule diffuses across the bilayer. The rate of flow of a solute across the bilayer is directly proportional to the difference in its concentration on the 2 sides of the membrane. Channels: channel protein forms a pore across the bilayers through which specific solutes can passively diffuse, when open these pores allow specific solutes through. Cells had to evolve ways of transferring water-soluble molecules in order to ingest essential nutrients, excrete metabolic waste products, and regulate intracellular ion concentrations. Specific mutations in human cells can result in diseases which interfere with some sort of transport process.
