The lipid bilayer of biological membranes is impermeable to charged molecules , including ions . The active transport via ion pumps is one of the specific mechanisms that ensure a regulated exchange of ions through the membrane or maintain the differences in concentration of ions between the two sides of the membrane. In contrast to ion channels , in principle an energetically favorable reaction is coupled with an energetically less favorable reaction.
Types of ion pumps
Basically, two types of ion pumps can be distinguished according to the energetic balance of the transport process:
- On the one hand, ion pumps of active transport, in which certain ions are transported against their respective electrochemical potential while consuming energy ( hydrolysis of ATP to ADP or also with light energy) . An example of this is the sodium-potassium ion pump ( ATPase ), which not only creates the resting potential in the nerve cells, but also maintains the osmotic balance between extra- and intracellular space in almost all cells of the human body.
- On the other hand, the term ion pumps also refers to those transmembrane proteins with enzyme activity, which now allow ions to pass along a gradient in the electrochemical potential and thereby convert ADP to ATP and thus use the energy of the gradient. In this way, for example, in the case of ATP synthase in the mitochondria , ATP is synthesized from ADP using a proton gradient .
- Sodium-Potassium Ion Pump
- Sarcoplasmic and Endoplasmic Reticulum Calcium Pump (SERCA)
- Proton pumps :
- Gerhard Klebe: Active substance design: Design and effect of medicinal substances (German Edition) . Spektrum Akademischer Verlag, 2009, ISBN 978-3-8274-2046-6 , p. 527 .
- Werner Müller-Esterl: Biochemistry - An introduction for physicians and natural scientists . Spektrum Akademischer Verlag, Heidelberg 2011, ISBN 978-3-8274-2003-9 , pp. 345-361 .
- Christian Hick, Astrid Hick: Intensive Physiology Course . Elsevier, Urban & Fischer Ort = Munich, 2009, ISBN 978-3-437-41893-8 , p. 252 .