electrochemical gradient

Examples of electrochemical gradient in the following topics:

• Secondary Active Transport

  • In secondary active transport, a molecule is moved down its electrochemical gradient as another is moved up its concentration gradient.
  • Instead, another molecule is moved up its concentration gradient, which generates an electrochemical gradient.
  • The molecule of interest is then transported down the electrochemical gradient.
  • As sodium ion concentrations build outside the plasma membrane because of the action of the primary active transport process, an electrochemical gradient is created.
  • An electrochemical gradient, created by primary active transport, can move other substances against their concentration gradients, a process called co-transport or secondary active transport.

• Electrochemical Gradient

  • The combined gradient of concentration and electrical charge that affects an ion is called its electrochemical gradient .
  • To move substances against a concentration or electrochemical gradient, the cell must use energy.
  • Active transport mechanisms, collectively called pumps, work against electrochemical gradients.
  • Electrochemical gradients arise from the combined effects of concentration gradients and electrical gradients.
  • Define an electrochemical gradient and describe how a cell moves substances against this gradient

• Chemiosmosis and Oxidative Phosphorylation

  • Chemiosmosis is the movement of ions across a selectively permeable membrane, down their electrochemical gradient.
  • The uneven distribution of H+ ions across the membrane establishes both concentration and electrical gradients (thus, an electrochemical gradient) owing to the hydrogen ions' positive charge and their aggregation on one side of the membrane.
  • If the membrane were open to diffusion by the hydrogen ions, the ions would tend to spontaneously diffuse back across into the matrix, driven by their electrochemical gradient.
  • This protein acts as a tiny generator turned by the force of the hydrogen ions diffusing through it, down their electrochemical gradient.
  • ATP synthase is a complex, molecular machine that uses a proton (H+) gradient to form ATP from ADP and inorganic phosphate (Pi).

• Proton Reduction

  • Anaerobic respiration utilizes highly reduced species - such as a proton gradient - to establish electrochemical membrane gradients.
  • An electrochemical gradient represents one of the many interchangeable forms of potential energy through which energy may be conserved.
  • An electrochemical gradient has two components.
  • Proton reduction is important for setting up electrochemical gradients for anaerobic respiration.
  • In contrast, fermentation does not utilize an electrochemical gradient.

• Primary Active Transport

  • The sodium-potassium pump maintains the electrochemical gradient of living cells by moving sodium in and potassium out of the cell.
  • 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.
  • Primary active transport moves ions across a membrane, creating an electrochemical gradient (electrogenic transport).
  • Describe how a cell moves sodium and potassium out of and into the cell against its electrochemical gradient

• Postsynaptic Potentials and Their Integration at the Synapse

  • Since the electrochemical gradient of sodium is steeper than that of potassium, a net depolarization occurs.

• Energy Conservation and Autotrophy in Archaea

  • Instead, in archaea such as the Halobacteria, light-activated ion pumps generate ion gradients by pumping ions out of the cell across the plasma membrane.
  • The energy stored in these electrochemical gradients is then converted into ATP by ATP synthase.

• F10 ATP Synthase

  • Energy is often released in the form of protium or H+, moving down an electrochemical gradient, such as from the lumen into the stroma of chloroplasts or from the inter-membrane space into the matrix in mitochondria.

• Sodium Pumps as an Alternative to Proton Pumps

  • Usually, an H+ cycle includes generation of the transmembrane electrochemical gradient of H+ (proton motive force) by primary transport systems (H+ pumps) and its use for ATP synthesis, solute transport, motility and reverse electron transport.
  • While certain Na+-dependent functions, like Na+-dependent uptake of melibiose, proline, and glutamate, have been observed in many bacteria, the ion gradients that served as energy sources for these transports have been generated by primary H+ pumps and converted to Na+ gradients by Na+/H+ antiporters.

• Equilibrium Constant and Cell Potential

  • If possible, a species will move from areas with higher electrochemical potential to areas with lower electrochemical potential.
  • In equilibrium, the electrochemical potential will be constant everywhere for each species.
  • It can also be used to determine the total voltage, or electromotive force, for a full electrochemical cell.
  • The Nernst equation gives a formula that relates the numerical values of the concentration gradient to the electrical gradient that balances it.
  • Empirically, an equilibrium situation would arise where the chemical concentration gradient could be balanced by an electrical gradient that opposes the movement of charge.