An amino acid will have the form shown at:
R-CH-C-OH (with an O double bonded to the C and a NH3+ bonded to the CH)
a) a pH of 7.0
b) any pH other than 7.0
c) a pH greater than its isoelectric point
d) its isoelectric point
e) a pH less than its isoelectric point
Would it be "e"?
yes
To determine which option is correct, we need to understand the concept of the isoelectric point (pI) of an amino acid. The isoelectric point is the pH at which an amino acid carries no net electrical charge.
For this particular amino acid, we can see that it has both a positively charged NH3+ group and a negatively charged COO- group. At lower pH values (acidic conditions), the NH3+ group will be protonated (H+ added), while at higher pH values (alkaline conditions), the COO- group will be deprotonated (H+ removed).
Option e) states that the amino acid will be at a pH less than its isoelectric point. Since the isoelectric point is the pH at which the amino acid carries no net electrical charge, the NH3+ group and COO- group will still be present. Thus, option e) is correct.
To determine the isoelectric point of the amino acid, we need to calculate the average of the pKa values (acid dissociation constant) of the NH3+ and COO- groups. This calculation involves considering the specific pKa values of the functional groups and their ionization states at different pH levels.