Amino Acid Structures

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Amino Acid Structures

Post by JBike » Mon May 14, 2018 8:46 pm

Hi Next Step,

This is probably a quick and easy question, but it is something I am stuck on. When I look up the structure of amino acids, why do I find two different structures for the same amino acid? I attached a picture of the two versions of Histidine to show you what I am talking about.
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On the left histidine, the R group is attached to the alpha carbon. The histidine on the right shows the R group attached to the amino group. Can you help me figure out why this is?

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Re: Amino Acid Structures

Post by Administrator » Wed May 23, 2018 9:25 am

Hey Justin, those are the same molecule. In both cases, the side chain is attached to a carbon (which is the alpha carbon, itself attached to an amino group and a carbonyl carbon).

Here's a color-coded version of the image to help clarify.
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