Na+-K+ channel pumps

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Model of the Na+/K+ pump
The Na+/K+ pumps are found in the neuronal plasma membrane and are a type of primary active transporter[1]. The role of the Na+/K+ pump is to maintain the electrochemical gradient of Na+ and K+. The Na+/K+ pumps are a type of ATPase they use the energy produced from the spliting of the ATP via hydrolysis to actively transport Na+ out of the axon and pump K+ into the axon. The Na+/K+ pump is a carrier protein, thus requires a change in conformation in order to move the ions across the membrane, for every 3 Na+ pumped out there are 2 K+ that have been pumped in. The Na/K+ pumps establish a resting potential of -70mv, this is a negative voltage as the outside of the cell is more positive than commpared with the inside of the cell. The Na+/K+ pump is described as being electrogenic as it creates a change in electrical potential within the cell[2]

How An Na+/K+ Pump Works

The Na+/K+ pump has two different conformational states known as E1 and E2. 3 Na+ bind to the intracllular binding site, the phosphorlyation of the pump using the ATP causes the conformational change within the pump. The pump is now in conformational state E2, the 3 Na+ are released outside of the cell. The binding of the 2 K+ to the extracellular surface results in the dephosphorylation of the pump returning the configuration back to E1, once in the E1 conformation the 2K+ are released into the cell[3].

Reference 

  1. Siegel GJ, Agranoff BW, Albers RW, et al. Basic Neurochemistry: Molecular, Cellular and Medical Aspects-Chapter 5-Membrane Transtport.6th edition. Philadelphia: Lippincott-Raven; 1999.
  2. Alberts B., Johnson A., Lewis J., Raff. M, Roberts K. Walter P. Molecular Biology of The Cell- Chapter10-Membrane Structure. 5th Ed, New York: Garland Science. Taylor & Francis Group LLC. 2008
  3. Darnell J.E., Lodish H., Berk. A, Zipursky L., Matsudaira P., Baltimore D. Cell Biology. 4th edition. 4th Ed, London: W.H.Freeman & Co Ltd. 1999

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