What are the meanings of calcium in physiology?
Chemiosmotic roles of calcium

Chemiosmotic metabolism links biochemical reactions to chemical gradients across cellular membranes. Perhaps the most important reactions involved in these processes are photosynthesis and respiration. In eukaryotic photosynthesis, reaction centres imbedded in the thylakoid membrane generate a proton (hydrogen ion) gradient. This proton gradient (which can be measured as a Proton Motive Force) is then converted into ATP and NADPH. ATP and NADPH then take part in the Calvin cycle to convert CO2 into sugars. (Nicholls & Ferguson 1992)

Apart from photosynthesis and respiration, there are many other biochemical processes that involve chemiosmotic mechanisms. Several of them involve gradients of ionic calcium. As noted before, calcium concentrations are over a thousand times higher in extracellular space than in the cytosol (Hopkins 1991, p.93). Cellular reserves of calcium are found in the endoplasmic reticulum and brain tissue microsomes (ibid). Cytosolic calcium concentration is also affected by mitocondrial buffering (Nicholls & Ferguson 1992, pp. 209-212).



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Created 30/5/99