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TBR cbt #6 bio question regarding thyroid hormones

Discussion in 'MCAT Study Question Q&A' started by inquiry101, Jul 24, 2011.

  1. inquiry101

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    Do thyroid hormones contain a peptide bond? according to tbr's explanation for question # 142 on test #6, thyroid hormones don't contain a peptide bond.


    however, in EK BIO, thyroid hormones are peptide hormones and are lipid soluble
    page 103 top paragraph.

    im not sure what to make out of the tbr's explanation. anybody have any idea?
     
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  3. vayntraubinator

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  4. inquiry101

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    thats what i thought, thanks a lot!
     
  5. BerkReviewTeach

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    If the structure is as you show in that wikipedia link, where is the amide bond? That structure has an amino group on an alpha carbon, but there is no -NH-CO- connection. There is neither an amide nor peptide group in that molecule. You only get a peptide linkage if there are two amino acids connected head-to-tail.

    And for general clarity, a peptide linkage is a subgroup of amide bonds, but just because a molecule has an amide functionality does not make it a peptide linkage.

    When it comes to discrepencies between BR and other sources, I have found that BR is correct pretty much all of the time. It doesn't necessarily mean the other source is wrong, as often it's not exactly the same thing in the other book. But the one thing you can feel confident about is that if it's listed in BR, it has a 99.99% likelihood of being valid (except for those "suppose this were true" passages).
     
  6. Charles_Carmichael

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    Agree with this.

    I have never heard of thyroid hormones being referred to as peptide hormones. Perhaps EK meant peptide-derived hormones since they're derived from tyrosine residues of thyroglobulin (though that's still a bit of a stretch).
     
  7. CodeBlu

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    This.
     
  8. AFLATPEG

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    bump!



    what about Calcitonin? Calcitonin is a 32-amino acid linear polypeptide hormone that is produced in humans primarily by the parafollicular cells (also known as C-cells) of the thyroid.
     

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