Transport across cell membranes

Transport across cell membranes

1. osmosis

   • net movements of water molecules
     • over a partially permeamble membrane
       • down a conc gradient
         • from high water potential to low water potential
           • symbol for water potential - ψ
   • uses aquaporins

2. diffusion

   • facilitated
     • large
     • polar
     • uses transport proteins
       • channel
       • carrier
   • simple
     • mall
     • non polar
     • via phospholipid bilayer
   • net movement of particles
     • down conc gradient
       • high conc to low conc

3. co transport

   • synport
     • molecules move same way
   • antiport
     • molecules move opposite way

4. active transport

   • requires energy in form of ATP
   • against conc gradient
     • low conc to high conc
   • carrier proteins
     • molecules bind to protein
       • ATP binds to protein
         • ATP hydrolyses
           • releases moelcules binded to carrier portien to other side of membrane
           • produces ADP and a phosphate

5. examples

   • Na+/K+ pump
     • active transport
     • Na moves outs of cell
       • low conc of sodium in cell
       • Na moves into cell via contranpsort protein
         • brings glucose with it
           • against conc gradient
           • high conc of glucose in epithelial cell
           • glucose diffuses out of cell in capilary
             • faciliatated diffusion