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Homework Help: C nomenclature in aminoacids

  1. Sep 6, 2012 #1

    biological aminoacids are named a-aminoacids, because their functional unit is in a-carbon

    what is called a-carbon?

  2. jcsd
  3. Sep 6, 2012 #2


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    Staff: Mentor

  4. Sep 6, 2012 #3
    > The alpha carbon in organic chemistry refers to the first carbon that attaches to a functional group (the carbon is attached at the first, or alpha, position).

    1) the first starting from where?
    2) in aminoacids, why isnt the C of the COOH, the first carbon, since that carbon holds an OH, which is a functional group?
  5. Sep 6, 2012 #4


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    Gold Member

    1) Starting from functional group. In the example of ethyl alcohol, the carbon attached to -OH is alpha carbon.

    2) The -COOH is collectively a carboxylic functional group. -OH is Hydroxyl group, different from Carboxylic.


    C=O and C-O-H are attached to the same Carbon. So, the Carbon attached to this carbon is considered alpha carbon.

    Also, read the protein section in the link given by Borek. Alpha Carbon is "backbone" carbon attached to Carbonyl (C=O) group.
  6. Sep 7, 2012 #5
    which functional group exactly? is there a hierarchy of functional groups that we start first from?

    so only backbone carbons are considered?
  7. Sep 7, 2012 #6


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    Staff: Mentor

    Answered in the wikipedia article.
  8. Sep 11, 2012 #7
    ok, so exclusively in proteins and despite what happens in other molecules, we consider a-carbon, the carbon where the COOH binds to, just that

    but why "Polypeptide chains are described by starting at the amino terminus (known as the N-terminus) and sequentially naming each residue until the carboxyl terminus (the C-terminus) is reached" ?
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