Identification of Amino Acids
IDENTIFICATION OF AMINO ACIDS BY MEANS OF TITRATION CURVE
ABSTRACT
The aim of the experiment was to identify an unknown amino acid through acid-base titrations which was prepared in water to form an acidic solution. Each group prepared unknown amino acid hydrochloride. The pre-prepared basic solution was slowly added to the amino acid solution and pH change was closely observed using the pH meter. During these titrations the amino acid converted from cation to zwitterion to anion; zwitterion is an amino acid with a net charge of zero. The identity of the unknown amino acid was determined by establishing a titration curve with the pKa values and pI point and molecular weight were either directly or indirectly found through the titration curve.
INTRODUCTION
Amino acids are also known as the building blocks of proteins. They are constituted of the amine group –NH3, the carboxyl group –COOH, hydrogen and “R” group which is different for each amino acid. The “R” group gives the amino acid its name. in physiological systems where the pH is near neutrality, the amino acid will occur in its net charge containing a zero. Amino acids are classified as amphoteric substances since they can act as either an acid or a base. Due to the nature of amino acids a titration curve was employed to identify the unknown amino acid. A titration curve is the plot of pH versus the volume of titrant used. Due to the use of an amino acid the titrant occurred to be both an acid and a base. The acid was very useful because it was able to add a proton to the amino group. The typical amino acids contain a central tetrahedral carbon atom. Bonded to the α-carbon are hydrogen and a variable side chain. The resulting groups of amino acids contain one positive and one negative charge forming a neutral molecule known as a zwitterion. Two possible configurations for the α-carbon constitute non-identical mirror images known as isomers or enantiomers.
Amino acids join via peptide bonds. Carboxylic
ABSTRACT
The aim of the experiment was to identify an unknown amino acid through acid-base titrations which was prepared in water to form an acidic solution. Each group prepared unknown amino acid hydrochloride. The pre-prepared basic solution was slowly added to the amino acid solution and pH change was closely observed using the pH meter. During these titrations the amino acid converted from cation to zwitterion to anion; zwitterion is an amino acid with a net charge of zero. The identity of the unknown amino acid was determined by establishing a titration curve with the pKa values and pI point and molecular weight were either directly or indirectly found through the titration curve.
INTRODUCTION
Amino acids are also known as the building blocks of proteins. They are constituted of the amine group –NH3, the carboxyl group –COOH, hydrogen and “R” group which is different for each amino acid. The “R” group gives the amino acid its name. in physiological systems where the pH is near neutrality, the amino acid will occur in its net charge containing a zero. Amino acids are classified as amphoteric substances since they can act as either an acid or a base. Due to the nature of amino acids a titration curve was employed to identify the unknown amino acid. A titration curve is the plot of pH versus the volume of titrant used. Due to the use of an amino acid the titrant occurred to be both an acid and a base. The acid was very useful because it was able to add a proton to the amino group. The typical amino acids contain a central tetrahedral carbon atom. Bonded to the α-carbon are hydrogen and a variable side chain. The resulting groups of amino acids contain one positive and one negative charge forming a neutral molecule known as a zwitterion. Two possible configurations for the α-carbon constitute non-identical mirror images known as isomers or enantiomers.
Amino acids join via peptide bonds. Carboxylic
References: Reginald H. Garret and Charles M. Grisham, Biochemistry, Fourth edition pitkin, R. B. 1990, introductory biology laboratory manual,Shippensburg University.