Re: ATP as an energy source.

Hi Selim,

Great question! I love to see people thinking outside the box. From what I know and what I've found, unfortunately I do not think ATP can be used as a general energy source. To understand why, we must understand the structure of ATP, and how this structure gives ATP its energy for the cell.

Adenosine Tri-Phosphate (ATP) is made up of the nitrogen base adenine with a ribose sugar (exacly like the Adenosine in DNA). Off of the ribose comes three (Tri) phosphate groups. Phosphate groups, if you remember, are negatively charged and putting three of them together makes for a very unstable covalent bond.

Consider when you place two magnets (same pole) end to end. What happens? There is resistance to place them end to end due to the electromagnetic force and if you aren't holding onto the magnets firmly, one will flip to the opposite pole. Picture the force that makes it difficult to put not only two but three magnets end to end in a chemical.

You can think of it as a energy spring within ATP. Because of this instability in the bond it is easily released in the enzymatic reactions throughout the cell. ATP turns into ADP (di-phosphate). ADP can be reloaded with another phosphate thus creating a nice recycling reaction between ATP and ADP.

Therefore, ATP acts as a energy-coupling agent NOT a fuel source. It is used by one set of reactions and then remade from another set of reactions to be resued over and over again.

The next question is how does this energy of ATP transfer over? The removal of the third phosphate group of ATP is covalently liked the the biomolecules of the cell, lipids and proteins.

Placing a negative charge on an already charged molecule is going to slightly shift the structure of that macromolecule. Therefore in the case of a protein, the placment of a phospate may change the structure to the point where its activity region is now closed and only the removal of that phosphate will open it up again. Therefore we have now chemically regulated the activation of a protein. The energy expended for this regulation was in the breakdown of ATP to ADP.

It is the effect of the negative phosphate charge on the protein or lipid that either can activate it or deactivate it. This is the simplest scenario, most proteins have multiple phosphate that are placed and removed in a sequential manner to regulate all sort of reactions, from binding other proteins to its activity state. Therefore, ATP helps drive most every reaction in the cell by its energy-coupling abilities of placing its third phosphate on the macromolecules of the cell. Fuel, on the other hand, needs something to burn in an oxygen rich environment. The energy from its burning is then used or converted into different types of energy to drive a process. ATP would just not give off the type of fuel energy because of its chemical makeup.

I hope that clears up your question.

Matt

You can learn more about the way that ATP is used in biochemical reactions by reviewing the pertinent chapters of a biochemistry textbook, such as Biochemistry, by L. Stryer. -- Moderator