Part IlIl: Coupled Reactions-Bioenergetics How is it that you have energy to wal
ID: 542607 • Letter: P
Question
Part IlIl: Coupled Reactions-Bioenergetics How is it that you have energy to walk, run, or study with friend How does your body store and use energy on a chances are you know something about t s? What is the source of that energy? molecular levet? Even if you're not a biology major he role of ATP (adenosine triphosphate) as an energy transport molecule within your cells. When ATP is hydrolyzed to ADP (adenosine di overall reaction releases energy, which can be used to power nonspontaneous ce such as making proteins from amino acids, or pumping ions across membranes. Th energy to make ATP from ADP comes from the metabolism of carbohydrates and fats. The thermodynamics applies to questions below relate to a few of these processes, illustrating how reactions occurring within your body right now. OH OH Above: Two representations of ATP (adenosine triphosphate) ou wil find that different textbooks write the chemical equation for the energy-releasing ATP ADP reaction in slightly different ways. Here are three examples, from three different biology/chemistry texts: (Pinorganic phosphate") ATP ADP + Pi + energy ATP + H2O ADP + H3PO4 G"--30.6 kJ a. One of the equations above often leads students to think (incorrectly) that bond-breaking releases energy. Identify the equation and explain why it is misleading.Explanation / Answer
A) in the given equaitons the misleading equation is
ATP ---> ADP + iP
The above equation shows only breaking of ATP to ADP and inorganic Phosphate.
So it may lead to think that bond breaking is releasing energy.
this is misleading as the above equation is incomplete infact there is a reaciton between ATP and water (hydrolysis) which leads to release of energy. So a water molecule is broken into H and OH (an endergonic process), and the the ADP and the Pi are combined with the OH and the H (making bond, exergonic process) which in turn results in overall release in energy.
B) The breaking of ATP molecule into ADP and inorgonic phosphate is assisted by water (hydrolysis of ATP).,as shown in the second equation
ATP + 2H2O --> ADP + H3PO4
Now we know that the overall free energy (delta G) is not just energy released or gained during a reaction infact is is decided by both enthalpy and entropy of a given reaction
DeltaG = Delta H - T Delta S
Delta H = change in enthalpy
Delta S = change in entropy
So here entropy is degree of disorderness
In case of hydrolysis of ATP the disorderness is in terms of water molecules
When ATP is dissociated into iP and ADP more water molecules get ordered (well arranged) near iP and ADP as compared to undissociated ATP.
This leads to overall decrease in value of Delta G making it more negative and hence the more feasibility of reaction.