MS

sodium potassium pump 

  • solute pump
    • amino acids, some sugars, and ions are transported by solute pumps
    • ATP energizes protein carriers, and in most cases, moves substances against concentration gradients
    • coupled systems: more than one substance
    • symport: both moved in the same direction
    • antiport: moved in opposite directions
    • one of the most important solute pumps is the Na+/K+ pump (sodium potassium pump)
    • it is an antiport
  • sodium potassium pump
    • Na+ and K+ are necessary for water balance of all cells
    • important for normal function of muscle and nerve cells
    • the pump has an order of operation
    • primary active transport: where energy is provided by the hydrolysis of ATP
    • secondary active transport/co-transport: which is driven indirectly by passive ion gradient created by the operation of the primary transport
    • primary active transport : Na+-K+ pump
    • K+ needs 10-20 times higher on the inside of the cell as compared to the outside
    • Na+ needs to be 10-20 higher on the outside of the cell as compared to the inside
    • each ion will slowly leak passively across the membrane due to their concentration gradients
    • thus, the pump is needed to maintain their concentration differences driving Na+ out of K+ into the cell
    • because they are being moved against their concentration gradients, it will require the use of ATP
    • thus, Na+-K+ ATPase is an enzyme within the pump protein that hydrolyzes ATP to get the energy to operate the pump
    • secondary active transport: co-transport
    • occurs as a result of the gradient created by primary active transport step out of the pump
    • Na+ will leak back into the cell by facilitated diffusion, other substances (amino acids, glucose, ions) get dragged along with it
      • they make use of their electrochemical gradient PE stored up across the membrane
      • they can even move against their own concentration gradients
  • why the Na/K pump is super cool
    • it creates a polarized cell membrane: one side is net positive, the other side is net negative
    • the polarized membranes established a resting membrane potential
    • this is PE created by ion concentration and distribution of net charge
    • it establishes an electrochemical gradient: an electrochemical potential for an ion
    • made of 2 parts
      • chemical PE: the PE due to a difference in chemical concentration
      • electrical PE: the electrochemical energy built up because of the uneven distribution of the positive charges
    • this gradient allows for some substances to move against their concentration gradients without the use of ATP