Re: energy in the tank

["John S. Denker" <jsd@MONMOUTH.COM>]

Jon Greenberg wrote:
> The problem, I think, is that bio folks tend to refer to reactions such as
> the hydrolysis of ATP as "breaking bonds". Of course bond-breaking is
> involved, but so is bond-making. The energy is released (if it is OK to say
> that) when the new bonds are formed, a step often ignored in biochem
> shorthand. So we wind up saying half-baked things such as, "Energy is
> released when a high energy phosphate bond in ATP is broken."

Ah, I think we're converging.

I think that we can agree that the following
notions are misconceptions (multiple copies of
the same misconception, perhaps):

 -?- ATP is a high-energy molecule because it
     has strong bonds.
 -?- Acetylene has high fuel value because the
     triple bond is really strong.

In fact ATP is a high-energy molecule because it
is relatively loosely bound, compared to the other
things it could turn into.

I suppose the triple bond is stronger than a single
bond, but it is tremendously weak compared to THREE
single bonds, which is what it is taking the place of.

Breaking bonds is indeed a critical part of the reaction
process, but in combustion the idea is to break weak
bonds and replace them with stronger bonds.

We shouldn't think that the bond is like the
rubber band in a rubber-band gun, that flies off
carrying energy when it is released.  THAT would
be a gross misconception.

ATP carries energy, just like a book on a high
shelf carries energy.  If you give it a chance
to re-arrange itself, it will do so, liberating
energy.

==============

To repeat:  There is nothing wrong with speaking
of ATP as a high-energy molecule.  Energy can be
stored and transported in the form of ATP.

OTOH it is not the breaking of ATP bonds that
liberates energy.  Breaking the ATP bond makes
room for some other bond to form, and _that_
liberates energy.