ATP or Its Hydrolysis: What Gives Energy?

[Ali Inam]

I have studied that ATP gets involved in almost all the reactions in our body, from cell processes to muscular movements and others.

But I just found out today (during a lecture), that whenever we talk about ATP or whenever energy is being required by ATP, ATP is hydrolysed into ADP and Phosphorus and then it provide the energy.

So, what really gives the energy, ATP or its hydrolysis.

Or does the hydrolysis of ATP releases energy to fulfil the energy needs of the process ?

 

[Ygggdrasil]

The hydrolysis of ATP provides the energy to power many of the processes in the cell. This occurs because ATP has a higher chemical potential energy than the products of hydrolysis, ADP and phosphate.

 

[Andy Resnick]

Expanding Ygggdrasil's comment a bit, the concentration ratio of ATP to ADP ([ATP]/[ADP]) in living cells is about 10^10 higher than equilibrium conditions. It is this displacement from equilibrium that provides free energy during hydrolysis.

 

[bobze]

I have studied that ATP gets involved in almost all the reactions in our body, from cell processes to muscular movements and others.

But I just found out today (during a lecture), that whenever we talk about ATP or whenever energy is being required by ATP, ATP is hydrolysed into ADP and Phosphorus and then it provide the energy.

So, what really gives the energy, ATP or its hydrolysis.

Or does the hydrolysis of ATP releases energy to fulfil the energy needs of the process ?

Don't think about it like that, think about it like a slide. Phosphates are high potential energy molecules, stacking them on adenosine "builds" potential energy (going up the slide via the steps). Each step is the addition of a phosphate, starting with AMP (monophosphate) up to ATP (triphosphate), at the top of the slide.

Lots of those cellular processes involve the transfer of the phosphate group from ATP via hydrolytic sites on the enzymes that catalyze them or transfer to an intermediary group ( http://en.wikipedia.org/wiki/Transition_state" ).

Consider for example, glutamine synthetase, which catalyzes the reaction of glutamate (glutamic acid) to glutamine.

By starting certain reactions at the top of the slide, cellular processes can overcome the thermodynamical "cost" of running reactions.

Once you've slide down the slide and are left with no phosphates, you have to invest some work in stacking them back on the top of the slide, which is where "real" energy production comes from-http://en.wikipedia.org/wiki/Oxidative_phosphorylation" and various other minor processes.