Saturday, August 13, 2011

Chemiosmosis and the proton – motive force: an overview


Chemiosmosis is an important, almost central part of the metabolism of living organisms. Inside the cells of these living organisms, ions (usually H+) need to be exchanged across membranes this process is called chemiosmosis.As defined, chemiosmosis is the process of diffusion of ions (usually H+ ions, also known as protons) across a selectively permeable membrane. As in osmosis, chemiosmosis leads to a concentration gradient of the diffusing ion across the membrane.1 This concentration gradient Is formed by the migration of ions which can be used for mechanical work, this phenomenon is called proton motive force. In many cells, this proton gradient provides the energy for the synthesis of adenosine triphosphate molecules (ATP). Adenosine triphosphate is considered by biologists to be the energy currency of life. It is a high-energy molecule that stores the energy needed by all the physiological mechanisms of the cell.2 Chemiosmosis in the cell involves the electron transport chain (ETC) and the ATP synthase, an enzyme that uses the proton gradient to catalyze ATP synthesis. The electron transport chain sets up consecutive oxidation / reduction reactions from O2 to H2O from different donors / acceptors to create a proton gradient. Al this steps occurs inside the mitochondrion, which is the cells powerhouse. Although some ATP is produced by glycolysis in the cytoplasm, far more is produced inside the mitochondrion of the cell. 
http://www.youtube.com/watch?v=4n8Fta3qGwY
1. "Adenosine Triphosphate." Web. 17 May 2011. <http://hyperphysics.phy-astr.gsu.edu/hbase/biology/atp.html>.
2.   "Topic 1: Components of Chemiosmosis." Connecting Concepts: Interactive Lessons in Biology. Web. 17 May 2011. <ats.doit.wisc.edu/Biology/cb/ch/t1.htm>.