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:

  • 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.

  • 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.

  • 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.

  • Transport of Electrolytes across Cell Membranes

    • In water, sodium chloride (NaCl) dissociates into the sodium ion (Na+) and the chloride ion (Cl–).
    • The most important ions, whose concentrations are very closely regulated in body fluids, are the cations sodium (Na+), potassium (K+), calcium (Ca+2),and magnesium (Mg+2); and the anions chloride (Cl-), carbonate (CO3-2), bicarbonate (HCO3-), and phosphate(PO3-).
    • Specific examples, such as GLUT and the Na/K, pump are included.

  • Nerve Impulse Transmission within a Neuron: Resting Potential

    • The negative charge within the cell is created by the cell membrane being more permeable to K+ movement than Na+ movement.
    • In neurons, potassium ions (K+) are maintained at high concentrations within the cell, while sodium ions (Na+) are maintained at high concentrations outside of the cell.
    • Recall that sodium-potassium pumps bring two K+ ions into the cell while removing three Na+ ions per ATP consumed.
    • The (a) resting membrane potential is a result of different concentrations of Na+ and K+ ions inside and outside the cell.
    • A nerve impulse causes Na+ to enter the cell, resulting in (b) depolarization.

  • ATP: Adenosine Triphosphate

    • The calculated ∆G for the hydrolysis of one mole of ATP into ADP and Pi is −7.3 kcal/mole (−30.5 kJ/mol).
    • The sodium-potassium pump (Na+/K+ pump) drives sodium out of the cell and potassium into the cell .
    • The Na+/K+ pump gains the free energy and undergoes a conformational change, allowing it to release three Na+ to the outside of the cell.
    • Two extracellular K+ ions bind to the protein, causing the protein to change shape again and discharge the phosphate.
    • By donating free energy to the Na+/K+ pump, phosphorylation drives the endergonic reaction.

  • Hormonal Regulation of the Excretory System

    • In contrast to ADH, which promotes the reabsorption of water to maintain proper water balance, aldosterone maintains proper water balance by enhancing Na+ reabsorption and K+ secretion from extracellular fluid of the cells in kidney tubules.
    • Because it is produced in the cortex of the adrenal gland and affects the concentrations of minerals Na+ and K+, aldosterone is referred to as a mineralocorticoid, a corticosteroid that affects ion and water balance.
    • It also prevents the loss of Na+ from sweat, saliva, and gastric juice.
    • The reabsorption of Na+ also results in the osmotic reabsorption of water, which alters blood volume and blood pressure.
    • Angiotensin II functions as a hormone, causing the release of the hormone aldosterone by the adrenal cortex, resulting in increased Na+ reabsorption, water retention, and an increase in blood pressure.

  • Malpighian Tubules of Insects

    • There are exchange pumps lining the tubules which actively transport H+ ions into the cell and K+ or Na+ ions out; water passively follows to form urine.

  • The Plasma Membrane and the Cytoplasm

    • These substances include ions such as Ca++, Na+, K+, and Cl–; nutrients including sugars, fatty acids, and amino acids; and waste products, particularly carbon dioxide (CO2), which must leave the cell.

  • Energy and Nutrient Requirements for Prokaryotes

    • Other important macronutrients are potassium (K), magnesium (Mg), calcium (Ca), and sodium (Na).