Where does the proton come in the reduction of NAD?

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In our curriculum biology textbook the reduction of NAD+ is depicted as follows:



NAD+ + 2 H+NADH + H+



If this proton in the products was not present in the reactants, then where does it come from? Alternatively, if it does not take part in the reaction, then why is it depicted?










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  • 2




    $begingroup$
    Can you reference the book? It's a bit weird, usually, NAD reduction is written simply like NAD+ + H+ >> NADH, you don't need the extra proton. Having some more info from the book paragraph you have found this reaction may help.
    $endgroup$
    – alec_djinn
    Mar 7 at 9:37















7












$begingroup$


In our curriculum biology textbook the reduction of NAD+ is depicted as follows:



NAD+ + 2 H+NADH + H+



If this proton in the products was not present in the reactants, then where does it come from? Alternatively, if it does not take part in the reaction, then why is it depicted?










share|improve this question











$endgroup$







  • 2




    $begingroup$
    Can you reference the book? It's a bit weird, usually, NAD reduction is written simply like NAD+ + H+ >> NADH, you don't need the extra proton. Having some more info from the book paragraph you have found this reaction may help.
    $endgroup$
    – alec_djinn
    Mar 7 at 9:37













7












7








7





$begingroup$


In our curriculum biology textbook the reduction of NAD+ is depicted as follows:



NAD+ + 2 H+NADH + H+



If this proton in the products was not present in the reactants, then where does it come from? Alternatively, if it does not take part in the reaction, then why is it depicted?










share|improve this question











$endgroup$




In our curriculum biology textbook the reduction of NAD+ is depicted as follows:



NAD+ + 2 H+NADH + H+



If this proton in the products was not present in the reactants, then where does it come from? Alternatively, if it does not take part in the reaction, then why is it depicted?







biochemistry






share|improve this question















share|improve this question













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edited Mar 7 at 14:11









David

12.8k42356




12.8k42356










asked Mar 7 at 7:45









HosseinHossein

383




383







  • 2




    $begingroup$
    Can you reference the book? It's a bit weird, usually, NAD reduction is written simply like NAD+ + H+ >> NADH, you don't need the extra proton. Having some more info from the book paragraph you have found this reaction may help.
    $endgroup$
    – alec_djinn
    Mar 7 at 9:37












  • 2




    $begingroup$
    Can you reference the book? It's a bit weird, usually, NAD reduction is written simply like NAD+ + H+ >> NADH, you don't need the extra proton. Having some more info from the book paragraph you have found this reaction may help.
    $endgroup$
    – alec_djinn
    Mar 7 at 9:37







2




2




$begingroup$
Can you reference the book? It's a bit weird, usually, NAD reduction is written simply like NAD+ + H+ >> NADH, you don't need the extra proton. Having some more info from the book paragraph you have found this reaction may help.
$endgroup$
– alec_djinn
Mar 7 at 9:37




$begingroup$
Can you reference the book? It's a bit weird, usually, NAD reduction is written simply like NAD+ + H+ >> NADH, you don't need the extra proton. Having some more info from the book paragraph you have found this reaction may help.
$endgroup$
– alec_djinn
Mar 7 at 9:37










2 Answers
2






active

oldest

votes


















9












$begingroup$

In a very simple way the equation describes the reaction. NAD is reduced using 2 hydrogen atoms. The two hydrogen atoms can come from one reactant (lactic acid fermentation) or from two (in a reaction of glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate; as shown in the figure below).




First of all, I will pick a particular example from glycolysis, catalyzed by glyceraldehyde-3-phosphate dehydrogenase.




enter image description here



Phosphate by its own has one hydrogen at cytosolic pH (because of the pKA). Thus in this reaction, there are two hydrogen atoms. One hydrogen atom is in the form of a hydride (a proton and two electrons) from the aldehyde group. This hydrogen atom is used to reduce NAD+ to NADH. A second hydrogen atom (in the form of a proton) comes from the phosphate. In the bisphosphoglycerate form, the proton dissociates from the phosphate group and is in solution.



The eventual fate of the electrons that were used to reduce NAD+ to NADH is the electron transport chain (in the mitochondria). In some cases, though, for example muscle cells in an anaerobic environment, or other species that don't have an electron transport chain, the electrons are used in fermentation of pyruvate to alcohol or lactic acid. When NADH donates its electrons in either case, it is then oxidized back to NAD+.




References:




  • Glycolysis

  • NAD

  • Lactic acid
    fermentation

  • HPO4





share|improve this answer











$endgroup$








  • 1




    $begingroup$
    Hi LDiago. I've edited your post to make it a little more readable, and added a little more explanation in a few parts. I hope you find it helpful! Please feel free to rollback if I've inadvertently changed the meaning, or you disagree with me on style.
    $endgroup$
    – De Novo
    Mar 13 at 5:55


















5












$begingroup$

A quick search on Wikipedia showed the same reaction you book is presenting.




In metabolism, the compound accepts or donates electrons in redox
reactions.[2] Such reactions (summarized in the formula below) involve
the removal of two hydrogen atoms from the reactant (R), in the form
of a hydride ion (H), and a proton (H+). The proton is released into
solution, while the reductant RH2 is oxidized and NAD+ reduced to NADH
by transfer of the hydride to the nicotinamide ring.



RH2 + NAD+ → NADH + H+ + R




This should answer your question.






share|improve this answer











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    2 Answers
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    active

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    2 Answers
    2






    active

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    active

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    9












    $begingroup$

    In a very simple way the equation describes the reaction. NAD is reduced using 2 hydrogen atoms. The two hydrogen atoms can come from one reactant (lactic acid fermentation) or from two (in a reaction of glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate; as shown in the figure below).




    First of all, I will pick a particular example from glycolysis, catalyzed by glyceraldehyde-3-phosphate dehydrogenase.




    enter image description here



    Phosphate by its own has one hydrogen at cytosolic pH (because of the pKA). Thus in this reaction, there are two hydrogen atoms. One hydrogen atom is in the form of a hydride (a proton and two electrons) from the aldehyde group. This hydrogen atom is used to reduce NAD+ to NADH. A second hydrogen atom (in the form of a proton) comes from the phosphate. In the bisphosphoglycerate form, the proton dissociates from the phosphate group and is in solution.



    The eventual fate of the electrons that were used to reduce NAD+ to NADH is the electron transport chain (in the mitochondria). In some cases, though, for example muscle cells in an anaerobic environment, or other species that don't have an electron transport chain, the electrons are used in fermentation of pyruvate to alcohol or lactic acid. When NADH donates its electrons in either case, it is then oxidized back to NAD+.




    References:




    • Glycolysis

    • NAD

    • Lactic acid
      fermentation

    • HPO4





    share|improve this answer











    $endgroup$








    • 1




      $begingroup$
      Hi LDiago. I've edited your post to make it a little more readable, and added a little more explanation in a few parts. I hope you find it helpful! Please feel free to rollback if I've inadvertently changed the meaning, or you disagree with me on style.
      $endgroup$
      – De Novo
      Mar 13 at 5:55















    9












    $begingroup$

    In a very simple way the equation describes the reaction. NAD is reduced using 2 hydrogen atoms. The two hydrogen atoms can come from one reactant (lactic acid fermentation) or from two (in a reaction of glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate; as shown in the figure below).




    First of all, I will pick a particular example from glycolysis, catalyzed by glyceraldehyde-3-phosphate dehydrogenase.




    enter image description here



    Phosphate by its own has one hydrogen at cytosolic pH (because of the pKA). Thus in this reaction, there are two hydrogen atoms. One hydrogen atom is in the form of a hydride (a proton and two electrons) from the aldehyde group. This hydrogen atom is used to reduce NAD+ to NADH. A second hydrogen atom (in the form of a proton) comes from the phosphate. In the bisphosphoglycerate form, the proton dissociates from the phosphate group and is in solution.



    The eventual fate of the electrons that were used to reduce NAD+ to NADH is the electron transport chain (in the mitochondria). In some cases, though, for example muscle cells in an anaerobic environment, or other species that don't have an electron transport chain, the electrons are used in fermentation of pyruvate to alcohol or lactic acid. When NADH donates its electrons in either case, it is then oxidized back to NAD+.




    References:




    • Glycolysis

    • NAD

    • Lactic acid
      fermentation

    • HPO4





    share|improve this answer











    $endgroup$








    • 1




      $begingroup$
      Hi LDiago. I've edited your post to make it a little more readable, and added a little more explanation in a few parts. I hope you find it helpful! Please feel free to rollback if I've inadvertently changed the meaning, or you disagree with me on style.
      $endgroup$
      – De Novo
      Mar 13 at 5:55













    9












    9








    9





    $begingroup$

    In a very simple way the equation describes the reaction. NAD is reduced using 2 hydrogen atoms. The two hydrogen atoms can come from one reactant (lactic acid fermentation) or from two (in a reaction of glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate; as shown in the figure below).




    First of all, I will pick a particular example from glycolysis, catalyzed by glyceraldehyde-3-phosphate dehydrogenase.




    enter image description here



    Phosphate by its own has one hydrogen at cytosolic pH (because of the pKA). Thus in this reaction, there are two hydrogen atoms. One hydrogen atom is in the form of a hydride (a proton and two electrons) from the aldehyde group. This hydrogen atom is used to reduce NAD+ to NADH. A second hydrogen atom (in the form of a proton) comes from the phosphate. In the bisphosphoglycerate form, the proton dissociates from the phosphate group and is in solution.



    The eventual fate of the electrons that were used to reduce NAD+ to NADH is the electron transport chain (in the mitochondria). In some cases, though, for example muscle cells in an anaerobic environment, or other species that don't have an electron transport chain, the electrons are used in fermentation of pyruvate to alcohol or lactic acid. When NADH donates its electrons in either case, it is then oxidized back to NAD+.




    References:




    • Glycolysis

    • NAD

    • Lactic acid
      fermentation

    • HPO4





    share|improve this answer











    $endgroup$



    In a very simple way the equation describes the reaction. NAD is reduced using 2 hydrogen atoms. The two hydrogen atoms can come from one reactant (lactic acid fermentation) or from two (in a reaction of glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate; as shown in the figure below).




    First of all, I will pick a particular example from glycolysis, catalyzed by glyceraldehyde-3-phosphate dehydrogenase.




    enter image description here



    Phosphate by its own has one hydrogen at cytosolic pH (because of the pKA). Thus in this reaction, there are two hydrogen atoms. One hydrogen atom is in the form of a hydride (a proton and two electrons) from the aldehyde group. This hydrogen atom is used to reduce NAD+ to NADH. A second hydrogen atom (in the form of a proton) comes from the phosphate. In the bisphosphoglycerate form, the proton dissociates from the phosphate group and is in solution.



    The eventual fate of the electrons that were used to reduce NAD+ to NADH is the electron transport chain (in the mitochondria). In some cases, though, for example muscle cells in an anaerobic environment, or other species that don't have an electron transport chain, the electrons are used in fermentation of pyruvate to alcohol or lactic acid. When NADH donates its electrons in either case, it is then oxidized back to NAD+.




    References:




    • Glycolysis

    • NAD

    • Lactic acid
      fermentation

    • HPO4






    share|improve this answer














    share|improve this answer



    share|improve this answer








    edited Mar 13 at 5:53









    De Novo

    7,38711441




    7,38711441










    answered Mar 7 at 10:31









    L.DiagoL.Diago

    1,5221425




    1,5221425







    • 1




      $begingroup$
      Hi LDiago. I've edited your post to make it a little more readable, and added a little more explanation in a few parts. I hope you find it helpful! Please feel free to rollback if I've inadvertently changed the meaning, or you disagree with me on style.
      $endgroup$
      – De Novo
      Mar 13 at 5:55












    • 1




      $begingroup$
      Hi LDiago. I've edited your post to make it a little more readable, and added a little more explanation in a few parts. I hope you find it helpful! Please feel free to rollback if I've inadvertently changed the meaning, or you disagree with me on style.
      $endgroup$
      – De Novo
      Mar 13 at 5:55







    1




    1




    $begingroup$
    Hi LDiago. I've edited your post to make it a little more readable, and added a little more explanation in a few parts. I hope you find it helpful! Please feel free to rollback if I've inadvertently changed the meaning, or you disagree with me on style.
    $endgroup$
    – De Novo
    Mar 13 at 5:55




    $begingroup$
    Hi LDiago. I've edited your post to make it a little more readable, and added a little more explanation in a few parts. I hope you find it helpful! Please feel free to rollback if I've inadvertently changed the meaning, or you disagree with me on style.
    $endgroup$
    – De Novo
    Mar 13 at 5:55











    5












    $begingroup$

    A quick search on Wikipedia showed the same reaction you book is presenting.




    In metabolism, the compound accepts or donates electrons in redox
    reactions.[2] Such reactions (summarized in the formula below) involve
    the removal of two hydrogen atoms from the reactant (R), in the form
    of a hydride ion (H), and a proton (H+). The proton is released into
    solution, while the reductant RH2 is oxidized and NAD+ reduced to NADH
    by transfer of the hydride to the nicotinamide ring.



    RH2 + NAD+ → NADH + H+ + R




    This should answer your question.






    share|improve this answer











    $endgroup$

















      5












      $begingroup$

      A quick search on Wikipedia showed the same reaction you book is presenting.




      In metabolism, the compound accepts or donates electrons in redox
      reactions.[2] Such reactions (summarized in the formula below) involve
      the removal of two hydrogen atoms from the reactant (R), in the form
      of a hydride ion (H), and a proton (H+). The proton is released into
      solution, while the reductant RH2 is oxidized and NAD+ reduced to NADH
      by transfer of the hydride to the nicotinamide ring.



      RH2 + NAD+ → NADH + H+ + R




      This should answer your question.






      share|improve this answer











      $endgroup$















        5












        5








        5





        $begingroup$

        A quick search on Wikipedia showed the same reaction you book is presenting.




        In metabolism, the compound accepts or donates electrons in redox
        reactions.[2] Such reactions (summarized in the formula below) involve
        the removal of two hydrogen atoms from the reactant (R), in the form
        of a hydride ion (H), and a proton (H+). The proton is released into
        solution, while the reductant RH2 is oxidized and NAD+ reduced to NADH
        by transfer of the hydride to the nicotinamide ring.



        RH2 + NAD+ → NADH + H+ + R




        This should answer your question.






        share|improve this answer











        $endgroup$



        A quick search on Wikipedia showed the same reaction you book is presenting.




        In metabolism, the compound accepts or donates electrons in redox
        reactions.[2] Such reactions (summarized in the formula below) involve
        the removal of two hydrogen atoms from the reactant (R), in the form
        of a hydride ion (H), and a proton (H+). The proton is released into
        solution, while the reductant RH2 is oxidized and NAD+ reduced to NADH
        by transfer of the hydride to the nicotinamide ring.



        RH2 + NAD+ → NADH + H+ + R




        This should answer your question.







        share|improve this answer














        share|improve this answer



        share|improve this answer








        edited Mar 7 at 14:30









        WYSIWYG

        31.4k749133




        31.4k749133










        answered Mar 7 at 10:55









        alec_djinnalec_djinn

        2,797728




        2,797728



























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