Question

1. i) (15 points) Sketch the titration curve of the following hypothetical amino acid, if you titrate it with 0.1M HCl. Assume your amino acid is at physiological pH at the beginning of the titration. Label everything on your titration curve clearly for full credit. pKa ( a NH3") = 9.2, pka ( a COOH) = 2.5, pka (RCOOH) = 4.5

Answer 1

Let the hypothetical amino acids that – CH – Coot at full forotonated form pka ķ the pk a = 2.5 pka -92 coolt us pka = 45 Henderson. Hasselbalch ecuation from rahere wo get, prapkat log te P= Protonated form DP-deproton- ated form & log Copy & propka ) = 10p**** Altaeka toe = 10 when, paypka then COAY EPI PAK Pka then CORI Col pH = ka then COP - CPI

Pka (2200H) Now the hypothetical amino acid dissor -ciates as Ant – CH – COOH 2.5 h – t – coo koon (4 ) It Pra (R-cout) N- t-con 14 ct – cool Con 4S coon 45 2 . here, physiological pH is felh here, pH7.4 7 pK a (x-cout) & pka (e-look) & pH 7.4 pka (&- Nit) So, at pH 7.4 the fore dominant form will se AH So, when the is added then horor following reactions cill occur H₂ –ct -coon 14 destacoon " 3k & Hel COO Coolt (AH) -CH – Coottu (A ) Het acht - coolt - H 2001 toh (AH₂) (AB)

curve acill be So, the titeration ato Ale Initial pH, predominant A4. Tre PH=Pk a = 45, A47=[AH) 25. CARI pt 45+--- 35 - - - 251 it caniv. pt, all convertats a oka = 23, & [A © 2nd canv.pr all converted o Att 2 9.5 eanivalent ta