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a level biology atp

"bond formation releases energy and bond cleavage uses energy in atp" i thought when the bonds are broken in atp energy is released, because of the equation "atp +h2o --> adp + inorganic phosphate + energy"
we did this in class and yes i don't understand the complicated definition but all we need to know is that bond broken releases energy
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Jpw1097
19
Original post by hello83
"bond formation releases energy and bond cleavage uses energy in atp" i thought when the bonds are broken in atp energy is released, because of the equation "atp +h2o --> adp + inorganic phosphate + energy"

Ahh, this never made sense to me either. The hydrolysis of ATP is indeed endothermic (that is, requires energy to break the bonds). However, the reaction is exergonic, this means it releases free energy.

The energy released during the reaction not only depends on whether it is endothermic or exothermic, but also whether there is an increase in entropy (entropy = disorder/chaos). ATP hydrolysis increases the entropy of the system, releasing energy. The energy released due to the increase in entropy is greater than that requires to break the bonds in ATP, and so free energy is released.
Reply 3
Avatar for Jpw1097
Jpw1097
19
Original post by lunariumxo
we did this in class and yes i don't understand the complicated definition but all we need to know is that bond broken releases energy

Nope, breaking bonds always requires input of energy. If breaking the bond increases the entropy (i.e. chaos or disorder) of the system, the reaction may release energy.
Original post by hello83
"bond formation releases energy and bond cleavage uses energy in atp" i thought when the bonds are broken in atp energy is released, because of the equation "atp +h2o --> adp + inorganic phosphate + energy"

You need to look at the Gibbs free energy of these reactions - it will make more sense then.
Original post by Jpw1097
Ahh, this never made sense to me either. The hydrolysis of ATP is indeed endothermic (that is, requires energy to break the bonds). However, the reaction is exergonic, this means it releases free energy.

The energy released during the reaction not only depends on whether it is endothermic or exothermic, but also whether there is an increase in entropy (entropy = disorder/chaos). ATP hydrolysis increases the entropy of the system, releasing energy. The energy released due to the increase in entropy is greater than that requires to break the bonds in ATP, and so free energy is released.

This is a good example of the perils of doing A level biology without A level chemistry: too many biology candidates simply don't even understand the terms 'entropy', 'exergonic', 'endergonic', 'free energy change' etc etc.

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