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Number of free protons in the cytosol of a single cell (volume 48µm^3) at a pH of 7

Value	3000 Protons
Organism	Budding yeast Saccharomyces cerevisiae
Reference	Orij R, Brul S, Smits GJ. Intracellular pH is a tightly controlled signal in yeast. Biochim Biophys Acta. 2011 Mar 21 1st page left columnPubMed ID21421024
Primary Source	Sherman F. Getting started with yeast. Methods Enzymol. 2002 350: 3-41 AND Perktold A, Zechmann B, Daum G, Zellnig G. Organelle association visualized by three-dimensional ultrastructural imaging of the yeast cell. FEMS Yeast Res. 2007 Jun7(4):629-38 AND Orij R, Postmus J, Ter Beek A, Brul S, Smits GJ. In vivo measurement of cytosolic and mitochondrial pH using a pH-sensitive GFP derivative in Saccharomyces cerevisiae reveals a relation between intracellular pH and growth. Microbiology. 2009 Jan155(Pt 1):268-78.PubMed ID12073320, 17419771, 19118367
Method	There are 10^-7mol protons in a liter, i.e. in 10^15µm^3. Calculating amount in 48µm^3: 48µm^3×10^-7mol/10^15µm^3=48×10^-22mole protons. Multiply by Avogadro's number: 48×10^-22mole×6×10^-23protons/mole=2880protons
Entered by	Uri M
ID	106510