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    • #14173
      nickname
      Participant

      I have to predict the positions of the glucose molecule that would become labeled from the 1-14C pyruvate (i.e, the label in the carboxyl group of pyruvate).

      a) Carbon-1

      b) carbon-2

      c) carbon-3

      d) carbon-4

      e) carbon-5

      d) carbon-6

      I first thought that carbons 1 and 6 were the correct answers, but they are not. Then I thought that 1,3,and 6 were correct but they are not. I know that pyruvate has 3 carbons and glucose has 6, but I know two how to approach this problem correctly. Any help will be appreciate it.

      Thank you and happy holidays!

    • #102412
      JackBean
      Participant

      look on the reactions, which take place in gluconeogenesis and their mechanism. It’s quite simple to trace the labeled atom…

    • #102413
      nickname
      Participant

      So for this kind of problem you look at where the new carbon is being attached to, correct?

    • #102429
      JackBean
      Participant

      look on this picture: http://upload.wikimedia.org/wikipedia/e … enesis.png
      and trace your atom! Just be carefull about symetrical molecules!

    • #102448
      USFBiomed
      Participant

      3,4… its a head to head bonding, not tail to tail, so 1,6 would be the reverse…

    • #102451
      nickname
      Participant

      Thank you USFBiomed. So since pyruvate is 3 carbons and glucose is 6 I connect the last of pyruvate with the first incoming carbon atom so 3 and 4 like you said. Is this explanation correct? Thanks again for your help and happy holidays!

    • #115707
      Moleculeus
      Participant

      When the two triosephosphates condense head-to-head to form a hexose, carbon 1 of the triose (originating from the carboxyl of pyruvate) forms carbons 3 and 4 of the hexose, carbon 2 of the triose forms carbons 2 and 5 of the hexose, and carbon 3 of the triose forms carbons 1 and 6 of the hexose.

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