how adenosine triphosphate is the ‘energy currency’ of cells? Is the molecule structured to trap and transfer energy or create it?
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To be an energy currency, a molecule has to be able to “bear” energy and the system it’s in has to be geared towards being able to put energy on it, and take energy off of it.
Think of it as a structure with two branches, and you can put a strong rubber band on both those branches with a lot of tension. To put on the band, you need to apply a lot of energy. Then this energy is transferred to tension in the band. The band is not very stable, all it takes is a flick and it falls off the branches, snapping and releasing all that tension.
In this analogy, the structure is adenosine, and this structure has three increasingly unstable (energetic) phosphate bonds (so three rubber bands of increasing strength). Organisms have evolved in a way where when food is broken down, by essentially breaking bonds, it eventually ends by taking this energy to make a bond, this phosphoanhydride bond, by adding a phosphate to ADP (a molecule that has only two phosphates) becoming ATP. There are other such molecules too, but ATP is the main one.
Organisms also evolved to use that currency. Think of it as other much bigger structures that when the band snaps off the currency molecule, it lands on another structure before fully shrinking back to its small size, also with branches, and this tension is now applied to a lesser extent to the branches of the new structure. This new structure now has tension on its skeleton, which means it can change shape and do something different to what it did before. This shape change was facilitated by the tension stored in the band when it was on the currency molecule.
It’s difficult to come up with accurate analogies, this one is pretty bad, but I hope it delivers the idea.
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