Monday, 7 January 2008

What does a "Pi" molecule refer to?

In maths, the answer would be quite straightforward - Pi is the ratio of the diameter of a circle to its circumference. Quite a magical number, and revered by some of the ancient Greeks. But that, unfortunately is not where the story ends.

Incredibly, "Pi" is used in a completely different way in biology. It symbolises a phosphate* group (PO4-). Thus, in reactions involving ATP's breakdown, you often see an equation like this:

ATP → ADP + Pi

* Not to be confused with phosphorus (P) - the atomic element which forms part of any phosphorus group.


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