Potassium

Examples of Potassium in the following topics:

• Potassium Balance Regulation

  • Potassium is predominantly an intracellular ion .
  • In an unprocessed diet potassium is much more plentiful than sodium.
  • If there is a high potassium intake, eg. 100 mmol, this would potentially increase the extracellular K+ level two times before the kidney could excrete the extra potassium.
  • The body buffers the extra potassium by equilibrating it within the cells.
  • A high plasma potassium increases aldosterone secretion and this increases the potassium loss from the body, restoring balance.

• Primary Active Transport

  • The sodium-potassium pump maintains the electrochemical gradient of living cells by moving sodium in and potassium out of the cell.
  • The sodium-potassium pump moves two K+ into the cell while moving three Na+ out of the cell.
  • The shape change increases the carrier's affinity for potassium ions, and two such ions attach to the protein.
  • For every three ions of sodium that move out, two ions of potassium move in.
  • Describe how a cell moves sodium and potassium out of and into the cell against its electrochemical gradient

• The Action Potential and Propagation

  • The repolarization or falling phase is caused by the slow closing of sodium channels and the opening of voltage-gated potassium channels.
  • As the sodium ion entry declines, the slow voltage-gated potassium channels open and potassium ions rush out of the cell.
  • Hyperpolarization is a phase where some potassium channels remain open and sodium channels reset.
  • A period of increased potassium permeability results in excessive potassium efflux before the potassium channels close.

• Nerve Impulse Transmission within a Neuron: Resting Potential

  • For most cells, this is potassium.
  • As potassium is also the ion with the most-negative equilibrium potential, usually the resting potential can be no more negative than the potassium equilibrium potential.
  • However, the neurons have far more potassium leakage channels than sodium leakage channels.
  • Therefore, potassium diffuses out of the cell at a much faster rate than sodium leaks in.
  • The actions of the sodium-potassium pump help to maintain the resting potential, once it is established.

• The Chemical Composition of Plants

  • Plants are composed of water, carbon-containing organics, and non-carbon-containing inorganic substances such as potassium and nitrogen.
  • Since plants require nutrients in the form of elements such as carbon and potassium, it is important to understand the chemical composition of plants.
  • Inorganic substances (which form the majority of the soil substance) are commonly called minerals: those required by plants include nitrogen (N) and potassium (K), for structure and regulation.

• Diuretics

  • There are three types of diuretics: thiazide, loop and potassium-sparing.
  • This results in several effects including bicarbonate retention in the urine, potassium retention in urine and decreased sodium absorption.
  • These are diuretics which do not promote the secretion of potassium into the urine; thus, potassium is spared and not lost as much as in other diuretics.
  • The term "potassium-sparing" refers to an effect rather than a mechanism or location; nonetheless, the term almost always refers to two specific classes that have their effect at similar locations: Aldosterone antagonists: spironolactone, which is a competitive antagonist of aldosterone.
  • A similar agent is potassium canreonate.

• 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.
  • Active transport is responsible for cells containing relatively high concentrations of potassium ions but low concentrations of sodium ions.
  • The mechanism responsible for this is the sodium-potassium pump, which moves these two ions in opposite directions across the plasma membrane.
  • It is now known that the carrier is an ATP-ase and that it pumps three sodium ions out of the cell for every two potassium ions pumped in.
  • The sodium-potassium pump was discovered in the 1950s by Danish scientist Jens Christian Skou.

• Electric Potential in Human

  • Typical ions used to generate resting potential include potassium, chloride, and bicarbonate.
  • This impulse is passed through the axon, a long extension of the cell, in the form of an electrical potential created by differing concentrations of sodium and potassium ions on either side of a membrane in the axon .
  • This impulse is passed through the axon, a long extension of the cell, in the form of an electrical potential created by differing concentrations of sodium and potassium ions on either side of a membrane in the axon.

• Resting Membrane Potentials

  • The three ions that appear in this equation are potassium (K+), sodium (Na+), and chloride (Cl−).
  • In most animal cells, the permeability to potassium is much higher in the resting state than the permeability to sodium.
  • Consequently, the resting potential is usually close to the potassium reversal potential.

• Postsynaptic Potentials and Their Integration at the Synapse

  • Sodium and potassium diffuse simultaneously but in opposite directions.
  • Since the electrochemical gradient of sodium is steeper than that of potassium, a net depolarization occurs.
  • Most inhibitory neurotransmitters hyperbolize the postsynaptic membrane by making it more permeable to potassium or chloride.