Na+-K+ ATPase

(noun)

An enzyme located in the plasma membrane of all animal cells that pumps sodium out of cells while pumping potassium into cells.

Related Terms

Examples of Na+-K+ ATPase in the following topics:

  • Sodium Pumps as an Alternative to Proton Pumps

    • Na+/K+-ATPase (Sodium-potassium adenosine triphosphatase, also known as Na+/K+ pump, sodium-potassium pump, or sodium pump) is an antiporter enzyme (EC 3.6.3.9) (an electrogenic transmembrane ATPase) located in the plasma membrane of all animal cells.
    • The Na+/K+-ATPase helps maintain resting potential, avail transport and regulate cellular volume.
    • In most animal cells, the Na+/K+-ATPase is responsible for about 1/5 of the cell's energy expenditure.
    • For neurons, the Na+/K+-ATPase can be responsible for up to 2/3 of the cell's energy expenditure.
    • This causes the dephosphorylation of the pump, reverting it to its previous conformational state, transporting the K+ ions into the cell.The unphosphorylated form of the pump has a higher affinity for Na+ ions than K+ ions, so the two bound K+ ions are released.

  • Primary Active Transport

    • One of the most important pumps in animals cells is the sodium-potassium pump (Na+-K+ ATPase), which maintains the electrochemical gradient (and the correct concentrations of Na+ and K+) in living cells.
    • The sodium-potassium pump moves two K+ into the cell while moving three Na+ out of the cell.
    • The Na+-K+ ATPase exists in two forms, depending on its orientation to the interior or exterior of the cell and its affinity for either sodium or potassium ions.

  • Body Fluid Composition

    • The reason for these specific sodium and potassium ion concentrations are Na+/K ATPase pumps, which facilitate the active transport of these ions.
    • The cations include: sodium (Na+ = 136-145 mEq/L), potassium (K+ = 3.5-5.5 mEq/L) and calcium (Ca2+ = 8.4-10.5 mEq/L).
    • Plasma is mostly water (93% by volume) and contains dissolved proteins (major proteins are fibrinogens, globulins and albumins), glucose, clotting factors, mineral ions (Na+, Ca++, Mg++, HCO3- Cl- etc.), hormones and carbon dioxide (plasma being the main medium for excretory product transportation).

  • Tubular Reabsorption

    • Active Transport-membrane bound ATPase pumps (such as NA+/K+ ATPase pumps) with carrier proteins carry substances across the plasma membranes of the kidney epithelial cells by consuming ATP.

  • Regulation of Water Output

    • It acts on mineralcorticoid receptors in the epithelial cells of the distal convoluted tubule and collecting duct, which increases their expression of Na+/K+ ATPase pumps and activates those pumps.

  • Electrochemical Gradient

    • At the same time, cells have higher concentrations of potassium (K+) and lower concentrations of sodium (Na+) than does the extracellular fluid.
    • In a living cell, the concentration gradient of Na+ tends to drive it into the cell, and the electrical gradient of Na+ (a positive ion) also tends to drive it inward to the negatively-charged interior.
    • The electrical gradient of K+, a positive ion, also tends to drive it into the cell, but the concentration gradient of K+ tends to drive K+ out of the cell.
    • Some examples of pumps for active transport are Na+-K+ ATPase, which carries sodium and potassium ions, and H+-K+ ATPase, which carries hydrogen and potassium ions.
    • Two other carrier protein pumps are Ca2+ ATPase and H+ ATPase, which carry only calcium and only hydrogen ions, respectively.

  • Nephron, Parts, and Histology

    • Water reabsorption in the proximal convoluted tubule occurs due to both passive diffusion across the basolateral membrane, and active transport from Na+/K+/ATPase pumps which actively transports sodium across the basolateral membrane.

  • Tubular Secretion

    • Active transport-movement of molecules via ATPase pumps, that transport the substance through the renal epithelial cell into the lumen of the nephron.
    • The substances that are secreted into the tubular fluid for removal from the body include: potassium ions (K+), hydrogen ions (H+), ammonium ions (NH4+), creatinine, urea, some hormones, and some drugs (e.g., penicillin). 
    • The movement of these ions also helps to conserve sodium bicarbonate (NaHCO3).

  • Nerve Impulse Transmission within a Neuron: Action Potential

    • At the same time, voltage-gated K+ channels open, allowing K+ to leave the cell.
    • These unmyelinated spaces are about one micrometer long and contain voltage gated Na+ and K+ channels.
    • At the same time, Na+ channels close. (4) The membrane becomes hyperpolarized as K+ ions continue to leave the cell.
    • The hyperpolarized membrane is in a refractory period and cannot fire. (5) The K+ channels close and the Na+/K+ transporter restores the resting potential.
    • Nodes contain voltage-gated K+ and Na+ channels.

  • Potassium Balance Regulation

    • Cell K+ concentration is about 150 mmol/l but varies in different organs.
    • It is present as an organic salt while sodium is added as NaCl.
    • Processing of foods replaces K+ with NaCl.
    • While the body can excrete a large K+ load it is unable to conserve K+.
    • On a zero K+ intake or in a person with K+ depletion there will still be a loss of K+ of 30-50 mmol/d in the urine and feces.