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Catabolism/Anabolism Endothermic/Exothermic Question

Discussion in 'DAT Discussions' started by rpatel8, Jul 26, 2011.

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  1. rpatel8

    rpatel8

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    I am confused. I don't know if its from overstudying or what but here is my question.

    So in biology, we are taught that catabolism releases energy and drives anabolism. For example, the hydrolysis of ATP releases energy and is exothermic. Anabolism requires energy to make more complex structures.

    But this is where I am confused. In chem, we are taught that breaking bonds requires energy and is endothermic and making bonds releases energy and is exothermic. Am I getting something backwards here or can these concepts not be related like I am trying to do?
  2. rpatel8

    rpatel8

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    I'm still confused. Anyone? haha
  3. koztelic

    koztelic

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    Great question...I'm confused about this as well...any clarification would help.
  4. flin5845

    flin5845

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    It is a good question. I think it's because the types of bonds. The bonds of ATP contain so much energy because of the electrostatic repulsion. And itay take a little bit of energy to break but it releases more energy than required.
  5. needzmoar

    needzmoar

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    I think you're getting the term exothermic and exergonic mixed. Hydrolysis of ATP is endothermic, but weakly.

    edit: also, the form of energy released in an exothermic reaction is typically heat or light. In exergonic, it's energy in the form of work that's released.

    edit edit: scanned the wiki page, cleavage of the phosphate bond is actually exothermic, too. It's exothermic because the HBonds formed between ADP and Pi is stronger than the cleaved bond. TIL
    Last edited: Jul 26, 2011
  6. radmazindds

    radmazindds

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    The ADP-P bond in ATP is exceptionally high in energy (aka very unstable) and breaking it is exothermic because that would stabilize the molecule.

    On the other hand, breaking the bonds of glucose, for example, DOES require an initial input of energy, but the net result is a higher yield of energy (like an investment).

    Not sure if that answered your question but that's how I'm seeing it.

  7. rpatel8

    rpatel8

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    On Topscore 1, there was a question that asked about the hydrolysis of ATP. The answer choices included "drives cellular work" AND "is an exergonic process". Wouldn't both of those be valid answer choices?
  8. radmazindds

    radmazindds

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    An exergonic process is one in which the products are more stable than the reactants.

    Sounds right to me. What did they have as the correct answer?

  9. rpatel8

    rpatel8

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    They had "drives cellular work" as the answer.
  10. mh0000

    mh0000

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    I think you're generalizing bonding. Some are thermodynamically favorable because the proiducts result in a lower potential energy. Think about ATP formation, you have to force three negatively charged phosphates in close proximity. This is quite a bit of potential energy, and will need an "investment" of energy. This is accomplished by the coupling of the breakdown of a molecule that releases even more free energy than is required to form the ATP. In the case of oxidative phosphorylation, the potential energy built up from the electrochemical gradient of the ETC provides this source of free energy. The subsequent "fall" of the protons is coupled to the formation of ATP. Likewise, the hydrolysis of ATp provides the free energy to drive lesser endothermic processes.
  11. radmazindds

    radmazindds

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    hm, i don't know. these things are bound to have some errors. or maybe I'm mistaken....

  12. crew09

    crew09 Member

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    damn.

    Checked 2 sources and they both say hydrolysis of ATP is EXERgonic.

    Wiki

    The description and typical textbook labeling of ATP phosphanhydridic bonds as "high energy bonds" can be very misleading to students. These bonds are in fact relatively weak. They do involve high energy electrons but the bonds themselves are quite easy to break.



    As noted below, energy is released by the hydrolysis of ATP when these weak bonds are broken - requiring a small input of energy, followed by the formation of new bonds and the release of a larger amount of energy as the total energy of the system is lowered and becomes more stable.

    hydrolysis of the phosphate groups in ATP is especially exergonic...
  13. toothhornet88

    toothhornet88 "Dr.IronFist"

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    Yeah I looked for it everywhere and could not come to an answer. I think it's a good idea to email each other's chem or bio professors and see what they say! :D
    I know it's summer and all but some professors actually do respond to emails during vacation
  14. needzmoar

    needzmoar

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    according to wiki, the enthalpy change is exothermic.
  15. crew09

    crew09 Member

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    Found 2 older threads that talk about this exact question, both strongly suggest that hydrolysis of ATP is EXERgonic.

    http://forums.studentdoctor.net/showthread.php?t=760207&highlight=
    http://forums.studentdoctor.net/showthread.php?t=821501&highlight=

    OP,

    I looked at your original question, and I think your over-generalizing.

    Exregonic rxns still require a small input of energy to overcome Energy of Activation. Simply requiring energy to perform a rxn doens't mean it's Endergonic.

    I hope I didnt confuse you more.....
    Anyone else feel free to add/correct.
    Last edited: Jul 26, 2011
  16. needzmoar

    needzmoar

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    it's both exothermic and exergonic.

    http://en.wikipedia.org/wiki/Adenosine_triphosphate

    5th paragraph under properties
  17. crew09

    crew09 Member

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    Thanks.

    Makes sense, I think we were confusing change in free energy spontaneous/nonspontaenous (-gonic) vs. enthalpy (-thermic) absorption/release of thermal energy.

    I think OP meant -gonic in his original question, either way doens't matter i'm sure he's gonna lay waste to the DAT and post a killer breakdown tomorrow :)
  18. KHOWARD7

    KHOWARD7

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    In a single molecule:
    To break a bond requires energy
    To make a bond releases energy

    Catabolism is a reaction with reactants and products.

    In catabolism, old bonds are broken (which requires energy) and new bonds are made (which releases energy). When you balance out the net energy of this reaction/catabolic process, it is found that the required energy to break the bonds is LESS than the energy that was released when making the new bonds.

    Macromolecule bond breaking_energy required < Micromolecule bond making_energy released

    NET result: energy released

    Essentially, the smaller molecules are more STABLE than the macromolecules.
    Why? Because a release of energy puts you in a lower energy state making you more stable

    Keep this thought process bolted in mind for all reactions (bio/orgo/chem)
    Last edited: Aug 28, 2011
  19. Demps

    Demps

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    Even though I like how you put together things to make sense, but it always troubled to make sense how in bio... ATP hydrolysis (breaks bond) is exergonic and releases energy and in GC... you release energy from making a bond in exothermic reaction.

    My conclusion was just to treat them separately, don't try to link them you will just confuse yourself even more. Whatever was taught in bio, just try to make sense within bio topic itself and vice versa for other subjects.
  20. needzmoar

    needzmoar

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    According to wiki, the HBonds between ADP and Pi are stronger than the cleaved ATP bond

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