Identify an Amino Acid

Topics: Acid, Amino acid, Amine Pages: 2 (529 words) Published: April 2, 2013
Introduction Proteins are very important to the diet of all animals because they are essential for the function of all cellular activity (Baldwin, 2003). Catalyzing chemical reactions in the body, providing storage and transport as well as antibodies for our immune system are just a few of the many vital roles of proteins. Amino acids are the building blocks of proteins and there are twenty amino acids utilized by biological life (Baldwin, 2003). The basic structure of all amino acids consists of a carboxyl group, an amino group and a hydrogen atom bonded to a carbon called the alpha carbon (Baldwin, 2003). The fourth constituent is an R group which is what give each amino acid its special properties. Amino acids have both positive and negative properties which means, when an amino acid lacking an ionizable R group is dissolved in water it can act as either an acid or a base (Clark, 2004). A molecule that displays both acidic and basic properties is called a zwitterion (Clark, 2004). This is due to the carboxylate group (-COO-) ability to be protonated to a carboxylate group (-COOH) as well as the amine group (-NH+3) to deprotonated to form (-NH2). In some cases the R group can be ionized as well. If a strong acid such as hydrochloric acid (HCl) is added to an amino acid solution, the HCl will donate a proton to carboxylate group to form the carboxyl acid group and therefore, make the solution acidic. (Clark, 2004). On the other hand, a strong base such as NaOH will accept a proton to form water, making the solution basic. (Clark, 2004). The Pka is the tendency of a group to give up a proton with its tendency decreasing ten times as the pKa increases by one unit (Nelson & Cox, 2008, p. 79). Since there are multiple positions in which protonation can occur they can be more that one pKa. For example, in a titration of an amino acid with an acid, the pk1 will be reached when the (–COO) group gains its proton...
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