Potential & Kinetic Energy of ATP in Krebs Cycle - Apology for Mistake

[Similibus]

Sincere apologies for my last post - I tried to delete the post but the thread is locked. I apologise sincerely if I did something wrong. I am sincere in my questions and have no desire to cause trouble.

Please could somebody tell me what the potential energy, that is generated in the Krebs cycle and 'stored' as ATP, is referred to? Both as energy potential and also as energy when it is released? Does physics currently have a collective name for this? Is it kinetic energy?

I am sorry if I am being thick, or if I have done something wrong again!

Regards
Sim

 

[atyy]

Somewhere in here? Someone else should be able to give you a short answer but it's not in my competence.

http://www.wwnorton.com/college/chemistry/gilbert/overview/ch6.htm
http://www.wwnorton.com/college/chemistry/gilbert/overview/ch11.htm
http://www.wwnorton.com/college/chemistry/gilbert/overview/ch12.htm
http://www.wwnorton.com/college/chemistry/gilbert/overview/ch13.htm

 

[Similibus]

Fantastic! Thank you!

 

[Dale]

Please could somebody tell me what the potential energy, that is generated in the Krebs cycle and 'stored' as ATP, is referred to?

Chemical energy.

 

[Andy Resnick]

The body stores energy in ATP by maintaining a concentration imbalance between ATP and ADP. That is, the relevant energy is the Gibbs free energy, expressed in terms of how far from equilibrium the relative concentration is set at- in mammalian cells, the relative concentration of ATP to ADP, [ATP]/[ADP], is about 10 orders of magnitude different from equilibrium. Hydrolyzing a molecule of ATP to ADP releases some of this energy in a form able to perform (chemical) work.

More generally, cells often store energy in terms of the 'chemiosmotic potential': a concentration gradient can be made equivalent to an electrical potential (about 60 mV across the cell membrane, 150 mV across the mitochondrial membrane).

 

[Similibus]

Thank you for your replies. I am a self educated person and am finding all this truly fascinating! Sorry if I seem confused about some things - this isn't easy for me to understand!

The body stores energy in ATP by maintaining a concentration imbalance between ATP and ADP. That is, the relevant energy is the Gibbs free energy, expressed in terms of how far from equilibrium the relative concentration is set at- in mammalian cells, the relative concentration of ATP to ADP, [ATP]/[ADP], is about 10 orders of magnitude different from equilibrium. Hydrolyzing a molecule of ATP to ADP releases some of this energy in a form able to perform (chemical) work.

So the chemical energy stored in molecular bonds is released as these bonds are broken, making energy available for chemical work? Please may I ask what force is responsible for the chemical bonds? Is this strong and weak nuclear forces, or am I way off? Do forces of gravitation or electromagnetism come into it at all?

Also, if it is not too long an answer - how is this energy potential made available to a muscle cell so that I can peddle a bicycle, for example? And how is the energy made available to the muscle cell on an 'on demand' basis, such as during periods of intense activity? Is ATP production increased as the ratio of ATP/ADP moves towards equilibrium - a negative feedback system?

More generally, cells often store energy in terms of the 'chemiosmotic potential': a concentration gradient can be made equivalent to an electrical potential (about 60 mV across the cell membrane, 150 mV across the mitochondrial membrane).

Thank you for that information - I was under the impression that all of the body's energy was generated through the Krebs cycle and stored as ATP! Please may I ask, where does the cell find this energy? Is a 'concentration gradient' due to a differing ratio of +/- ions, generating a small electrical potential (?ionisation energy)- and is electromagnetic force responsible for the energy potential here? Also do you know how the cell utilises this energy, in terms of the muscle cell as in the questions above? Lastly, is there a reason that the 'concentration gradient' is greater across the mitochondrial membrane, other than an increased +/- differential?

I am interested in how the cell functions as a 'generator' or 'dynamo' for the energy required by living things, and what forces come into play in the generation of this energy. Please let me know if I should be posting in a different forum.

many thanks for any replies,
Sim

 

[russ_watters]

Please may I ask what force is responsible for the chemical bonds? Is this strong and weak nuclear forces, or am I way off? Do forces of gravitation or electromagnetism come into it at all?

Molecular bonds are with electrons, therefore, the electromagnetic force.

 

[Andy Resnick]

<snip>

So the chemical energy stored in molecular bonds is released as these bonds are broken, making energy available for chemical work?

<snip>

Definitely not- that is a common conceptual misunderstanding. One phosphate bond is identical to any other phosphate bond- *work* cannot be extracted by "breaking" a chemical bond, although heat may be generated.

The work is stored via a displacement from equilibrium. That displacement is a chemical concentration imbalance- either spatially (on either side of a membrane) or by the Gibbs free energy, by maintaining a solution with concentrations different from equilibrium conditions.

Here's a simple example: water has a normal pH of 7.0. Equal numbers of H and OH ions. Let me put work into the system by removing a lot of OH, and holding the pH of my 'water' at 2.0. I now have the ability to extract work from that solution by using those excess H ions.