I know that breaking the phosphate group off is exothemic, and something is going on with entropy and free energy for the hydrolysis of ATP to be used for work in a cell.

Take active transport, needs a conformation change in a protein to work - how does the cell use ATP to bring around this structure change?

One exothermic is not the same as exergonic. The former deals with enthalpy, and the latter deals with Gibbs' free energy. The hydrolysis of ATP is thermodynamically favorable, but the reasons are both enthalpic and entropic. Two, you are asking two questions. The first is about mechanical work, and the second is about active transport. It is also worth pointing out that not all active transport requires ATP, but some does. Three, when you say "structural change" are you referring to the enzyme which is utilizing ATP or to something else.

 

It also seems to me that your question might be about the general phenomenon of biological coupling, or it might be very specific, such as a question about the catalytic cycle of the actin•myosin complex. Perhaps you can help us by providing some context.

Edited March 24, 201510 yr by BabcockHall