Ibuki.Missions
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How can ATP release energy if the phosphate is broken off, if energy is used up when breaking bonds and released when making bonds?
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Neurocandid
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(Original post by Ibuki.Missions)
How can ATP release energy if the phosphate is broken off, if energy is used up when breaking bonds and released when making bonds?
Adenosine triphosphate (ATP) consists of an adenosine molecule bonded to three phophate groups in a row. In a process called cellular respiration, chemical energy in food is converted into chemical energy that the cell can use, and stores it in molecules of ATP. This occurs when a molecule of adenosine diphosphate (ADP) uses the energy released during cellular respiration to bond with a third phosphate group, becoming a molecule of ATP. So the energy from cellular respiration is stored in the bond between the 2nd and 3rd phosphate groups of ATP. When the cell needs energy to do work, ATP loses its 3rd phosphate group, releasing energy stored in the bond that the cell can use to do work. Now its back to being ADP and is ready to store the energy from respiration by bonding with a 3rd phosphate group

Hope this answers your question?
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Uori32qu
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(Original post by Ibuki.Missions)
How can ATP release energy if the phosphate is broken off, if energy is used up when breaking bonds and released when making bonds?
I had never actually thought about this before, but found it has to do with the water molecules forming more bonds with the Pi + ADP than when in the ATP form. There's a good answer here: https://chemistry.stackexchange.com/...energy-release
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davidthomasjnr
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(Original post by Ibuki.Missions)
How can ATP release energy if the phosphate is broken off, if energy is used up when breaking bonds and released when making bonds?
This relates to the following equation: ATP --> ADP + Pi (is reversible)

Yes you are correct, breaking bonds is an endothermic process; energy has to be absorbed for bonds to be broken. However, the Pi group reacts with water to form orthophosphate and ADP gains a hydrogen (is reduced) during this process. So the net energy in the system is exothermic, as the net energy from the bonds formed in the system is higher than the energy used to break them. Moreover, it is kinetically favourable for ATP to be hydrolysed to ADP, as the highly negative, polar phosphate groups mean the molecule is relatively unstable. So it is a very rapid reaction that can release a lot of energy. Coupled with the mechanisms to regenerate ATP, this explains why ATP is a very useful molecule for cells.
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TODTEMPLE01
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I've been taught that when the phosphate is broken off, there is increased resonance of the phosphate group double bond that releases energy and also there is repulsion between the negatively charged phosphates (one that is released and those on newly-formed ADP) that creates and releases energy
Last edited by TODTEMPLE01; 3 months ago
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Reality Check
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(Original post by Ibuki.Missions)
How can ATP release energy if the phosphate is broken off, if energy is used up when breaking bonds and released when making bonds?
Do a quick energy profile diagram on the reaction ATP - ADP +Pi and it will be clear.
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BelleWest23
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(Original post by TODTEMPLE01)
I've been taught in lectures that when the phosphate is broken off, there is increased resonance of the phosphate group double bond that releases energy and also there is repulsion between the negatively charged phosphates (one that is released and those on newly-formed ADP) that creates and releases energy
The same as what my former tutor said.
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davidthomasjnr
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(Original post by BelleWest23)
The same as what my former tutor said.
It's essentially like putting petrol on a fire
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BelleWest23
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(Original post by davidthomasjnr)
It's essentially like putting petrol on a fire
exactly why he's now a 'former tutor'
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