Homework Help Question & Answers
#1) a) The pK1, pK2, and pKR for the amino acid histidine are 1.8, 9.3, and…
#1)
a) The pK1, pK2, and pKR for the amino acid histidine are 1.8, 9.3, and 6.0, respectively. At pH 4.0 would be charged predominantly as follows:
|
A |
a-carboxylate 0, a-amino +1, imidazole +1, net charge +2 |
|
B |
a-carboxylate +1, a-amino +1, imidazole −1, net charge +1 |
|
C |
a-carboxylate −1, a-amino +1, imidazole 0, net charge 0 |
|
D |
a-carboxylate +1, a-amino 0, imidazole −1, net charge 0 |
|
E |
a-carboxylate −1, a-amino +1, imidazole +1, net charge +1 |
b) The pK1, pK2, and pKR for the amino acid arginine are 1.8, 9.0, and 12.5, respectively. At pH 7.0 arginine would be charged predominantly as follows:
|
A |
a-carboxylate +1, a-amino 0, guanidino -1, net charge 0 |
|
B |
a-carboxylate 0, a-amino 0, guanidino +1, net charge +1 |
|
C |
a-carboxylate −1, a-amino +1, guanidino +1, net charge +1 |
|
D |
a-carboxylate −1, a-amino 0, guanidino +1, net charge 0 |
|
E |
a-carboxylate +1, a-amino −1, guanidino −1, net charge −1 |
c) The pK1, pK2, and pKR for the amino acid aspartic acid are 2.0, 9.9, and 3.9, respectively. At pH 7.0, aspartic acid would be charged predominantly as follows:
|
A |
a-carboxylate +1, a-amino +1, b-carboxylate +1, net charge +3 |
|
B |
a-carboxylate 0, a-amino +1, b-carboxylate 0, net charge +1 |
|
C |
a-carboxylate 0, a-amino −1, b-carboxylate 0, net charge −1 |
|
D |
a-carboxylate +1, a-amino −1, b-carboxylate +1, net charge +1 |
|
E |
a-carboxylate −1, a-amino +1, b-carboxylate −1, net charge −1 |
