15 November 2010


At every moment, one hundred million million haeomoglobin molecules, which are extremely complex structures, are being destroyed in my body and an equal number created.
-- Julian Barbour


Emily said...

A wonderful thought; I guess you can't step in the same bloodstream twice.

Caspar Henderson said...

Indeed. I don't doubt Barbour's figures are in the right ball park (he is, after all, a remarkable physicist; for an introduction to his ideas see a short documentary called Killing Time), but I have been wondering how such a figure is derived.

Wikipedia quotes 2.4 million red blood cells being produced in a human body every second. (Writing in 1674, van Leeuwenhoek described each one as '25,000 times smaller than a fine grain of sand.') I've found an estimate of 280 million molecules of haemoglobin in a typical red blood cell. If both figures are correct then 672 million haemoglobin molecules are made (and a roughly equal number destroyed) in a human body every second.