DAT Destroyer Ochem 174 - 2011

[Demo0710]

Consider the amino acid serine:

Here is a link for what it looks like: http://upload.wikimedia.org/wikiped...rine-skeletal.png/273px-L-serine-skeletal.png

What will the amino acid look like at physiological pH?

The correct answer has it at as NH3+ and COO-.

Can someone explain this? Thanks!

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[Mr Dental]

The amine side has a pKa=9~10 and the carboxylic acid side has a pKa=2ish.
At physiological pH of 7, NH3+ and COO- will predominate.

If pH>pKa, then the basic form predominates.
If pH<pKa, then the acidic form predominates.

 

[Dotoday]

I agree with Mr. Dental. Since the pka of Amino group is around 9, then at physiological ph it will.be protonated ( gain an H). Carboxy group has a pka of around 3, therefore at physiological ph ( ph= 7), it will loose an H. Hope this helps.

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