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OCHEM configurations

Discussion in 'MCAT: Medical College Admissions Test' started by maxsmyles, Dec 31, 2008.

  1. maxsmyles

    2+ Year Member

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    I had trouble with some configurations MCAT Ochem needs u to know:


    ok, so lets deal with (+ and -), (L and D), and (S and R)

    correct me if I am wrong.

    S and R deal with absolute configurations (depends on how substituents are bonded.)

    (L and D) deal with the way light is bent.

    (-) is another term for L and (+) is another term for D?

    also, we have L amino acids and D sugars. Do we specifically have S or R sugars and amino acids?

    thanks
     
  2. G1SG2

    5+ Year Member

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    correct

    Yes, it refers to optical activity...

    Our naturally occurring amino acids have the L configuration.
     
  3. LaCasta

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    All L are S all R are D but these do not indicate whether they are ± as optical rotation can't be predicted by absolute config
     
  4. medicant

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    yes and no. (+) and (-) refer to the rotation of plane polarized light as it passes through an enantiopure solution of the compound in question. L and R are relative terms that relate common biomolecules like amino acids and sugars to glyceraldehyde - it so happens that L molecules turned out to be S, and R molecules R for the naturally occuring molecules...one can imagine non-biological examples, however, where this would not be the case. S and R, as was said, refer to absolute configuration.
     

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