Solution: Given the following equilibrium, at what pH would the molecule most likely be in a zwitterionic form?H3N+-CH2-COOH ⇌ H3N+-CH2-COO- ⇌ H2N-CH2-COO-                          pKa1: 2.4                     pKa2: 9.6A. 1.2B. 2.4C. 6.7D. 10.5E. 13.7

Problem

Given the following equilibrium, at what pH would the molecule most likely be in a zwitterionic form?

H3N+-CH2-COOH ⇌ H3N+-CH2-COO- ⇌ H2N-CH2-COO-

                          pKa1: 2.4                     pKa2: 9.6

A. 1.2

B. 2.4

C. 6.7

D. 10.5

E. 13.7

Solution

Amino acids, peptides, and proteins can have different net charges, depending on the pH and the amount of ionizable groups present in the molecule. The given molecule is glycine, which only has two ionizable groups.

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