MadSci Network: Biochemistry
Query:

Re: why ATP is used as energy currency in place of DHAP

Date: Tue Jul 29 20:00:15 2003
Posted By: Neil Saunders, Research fellow
Area of science: Biochemistry
ID: 1058535411.Bc
Message:

Hi Ritankar,

Thanks for your question, it's an interesting one.

If you can, I suggest you try to find a book titled "Bioenergetics 2", by D. Nicholls and S. Ferguson. It contains a very good chapter on quantitative bioenergetics. Basically, the answer to your question is that we have to consider more than the Gibbs free energy change for hydrolysis when we want to know how likely it is that a particular reaction will occur in the cell. The reason that all organisms use ATP as energy currency is to do with what's called the mass action ratio. In other words, reactions in cells tend to push the reaction ADP + Pi -> ATP in the ATP direction, away from equilibrium and so large amounts of ATP are available to drive other reactions. In fact in a hypothetical cell, any reaction that maintained a product a large amount away from equilibrium (e.g. the glucose -> glucose-6-phosphate reaction) could be used. As to why we use ATP, we can only speculate that this reaction was selected early in the history of cells and has persisted to the present day.

Hope this helps with your question,

Neil


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