Chapter 16, Problem 16.26UKC

(a)

Interpretation Introduction

Interpretation:

Amino acid in ball and stick model below has to be determined.

Concept Introduction:

Amino acids are the biomolecules that contain an amino group, carboxylic acid group, and an alkyl chain. Beside basic amino acid glycine, all amino acids contain chirality centers. Amino acids can exist in different forms depend on value of $\text{pH}$ of aqueous solution. These forms can be explained as follows:

(1) Neutral amino acids exist in their zwitterionic form at $\text{pH}$ value 6.

(2) Amino acids exist with net $+1$ charge after proton is accepted by carboxylate anion if $\text{pH}$ is lowered to 2 or less than 2.

(3) Amino acids exist with net $-1$ charge after proton is donated by ammonium cation if $\text{pH}$ is raised to 10 or higher than 10.

(4) At physiological $\text{pH}$ 7.4, neutral amino acids are mainly exist in their zwitterionic forms.

(5) Value of $\text{pH}$ that has neutral form of amino acid is known as isoelectric point of that amino acid. Isoelectric point of neutral amino acids is around 6.

(6) Isoelectric point of amino acids with additional carboxylic group is around 3.

(7) Isoelectric point of amino acids with additional basic nitrogen atom is around $7.6-10.8$.

(b)

Interpretation Introduction

Interpretation:

Three-letter and one-letter abbreviations for amino acid in ball and stick model below have to be determined.

Concept Introduction:

Refer to part (a).

(c)

Interpretation Introduction

Interpretation:

Amino acid form that presents at isoelectric point for amino acid represents below has to be determined.

Concept Introduction:

Refer to part (a).