peter90036
Forum Elite
Topics: 28
Posts: 315
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i never understood this fact (quoting here from Kaplan book)
lets say an 'acidic' amino acid...
R group has Carboxyl = aminoacid is Acidic , because the carboxyl dissociates in acidic range of pH (ph<7)
At physiologic pH R group is dissociated (ionized) ......as far as i know physiologic pH is >7...?
then the example: Aspirin is an acidic drug. to increase excretion pH of urine is raised to produce the ionized form.
so....mmm.... i dont get it...
does the 'acidic' aminoacid/protein dissociate in acidic or in basic pH ???
Edited by peter90036 on 06/24/08 - 12:32 PM
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| ajuth
Forum Newbie
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Posts: 1
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I believe aspirin has a pKa of about 3.5. This is good boecause in the stomach (pH ~ 1.5) it is protonated therefore facilitating transport across the gastric mucosa. I believe it would be ionized at physiological pH. I'm not sure what kaplan means. Maybe raising the pH ensures complete ionization of all aspirin molecules?
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| shazbaz
Forum Junior
Topics: 15
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I look at it like this...at acidic pH weak acids and bases both will be protonated....so this way weak acids will be uncharged and weak bases will be charged...and uncharged = easier excretion...so weak bases will be excreted in acidic urine
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| shazbaz
Forum Junior
Topics: 15
Posts: 51
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also from wat i know...acid amino acids are negatively charged at physiological pH and physiological pH is greater than 7 so they are not protonated and so charged. I am not a hundred percent sure about this part because i think pka values also have something to do here..so maybe others can add to this.
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