Examples of ion pump in the following topics:
-
- Ion channels are membrane proteins that allow ions to travel into or out of a cell.
- Most channels are specific (selective) for one ion.
- Ion pumps are not ion channels, but are critical membrane proteins that carry out active transport by using cellular energy (ATP) to "pump" the ions against their concentration gradient.
- Such ion pumps take in ions from one side of the membrane (decreasing its concentration there) and release them on the other side (increasing its concentration there).
- A schematic representation of an ion channel.
-
- 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 pump, while binding ATP, binds 3 intracellular Na+ ions.
- A conformational change in the pump exposes the Na+ ions to the outside.
- The phosphorylated form of the pump has a low affinity for Na+ ions, so they are released.The pump binds 2 extracellular K+ ions.
- 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.
-
- Typical ions used to generate resting potential include potassium, chloride, and bicarbonate.
- Potentials can change as ions move across the cell membrane.
- This can occur passively, as ions diffuse through ion channels in the membrane.
- Active transport of ions across a cell membrane is also a possibility.
- This involves ion pumps using energy to push an ion from an area of lower concentration to one of higher concentration.
-
- The cell membrane separates cytosol from extracellular fluid, but can pass through the membrane via specialized channels and pumps during passive and active transport.
- In contrast to extracellular fluid, cytosol has a high concentration of potassium ions and a low concentration of sodium ions.
- The reason for these specific sodium and potassium ion concentrations are Na+/K ATPase pumps, which facilitate the active transport of these ions.
- These pumps transport ions against their concentration gradients to maintain cytosol fluid composition of ions.
- Some of the electrolytes present in the transcellular fluid are sodium ions, chloride ions and bicarbonate ions.
-
- For example, transmembrane ion pumps in nerve cells use the energy from ATP to pump ions across the cell membrane and generate an action potential.
- The sodium-potassium pump (Na+/K+ pump) drives sodium out of the cell and potassium into 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.
- Sodium-potassium pumps use the energy derived from exergonic ATP hydrolysis to pump sodium and potassium ions across the cell membrane.
-
- Salt and other compounds that dissociate into their component ions are called electrolytes.
- In water, sodium chloride (NaCl) dissociates into the sodium ion (Na+) and the chloride ion (Cl–).
- The mechanisms that transport ions across membranes are facilitated diffusion and active transport.
- Active transport requires energy in the form of ATP conversion, carrier proteins, or pumps in order to move ions against the concentration gradient.
- Specific examples, such as GLUT and the Na/K, pump are included.
-
- Active transport mechanisms, collectively called pumps, work against electrochemical gradients.
- An important membrane adaption for active transport is the presence of specific carrier proteins or pumps to facilitate movement.
- 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.
- A uniporter carries one molecule or ion.
-
- Chemiosmosis is the movement of ions across a selectively permeable membrane, down their electrochemical gradient.
- The electrons cause conformation changes in the shapes of the proteins to pump H+ across a selectively permeable cell 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.
- However, many ions cannot diffuse through the nonpolar regions of phospholipid membranes without the aid of ion channels.
- At the end of the pathway, the electrons are used to reduce an oxygen molecule to oxygen ions.
-
- To enter or exit the neuron, ions must pass through special proteins called ion channels that span the membrane.
- Some ion channels need to be activated in order to open and allow ions to pass into or out of the cell.
- Ion channels that change their structure in response to voltage changes are called voltage-gated ion channels.
- The actions of the sodium-potassium pump help to maintain the resting potential, once it is established.
- Recall that sodium-potassium pumps bring two K+ ions into the cell while removing three Na+ ions per ATP consumed.
-
- 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.
- Three sodium ions bind to the protein.
- For every three ions of sodium that move out, two ions of potassium move in.
- The sodium-potassium pump is, therefore, an electrogenic pump (a pump that creates a charge imbalance), creating an electrical imbalance across the membrane and contributing to the membrane potential.