Essential Amino Acids

1. Essential and Non-essential Amino acids

Amino acids are organic compounds which contain both an amino group and a carboxyl group and may be divided into two groups basing on whether they are produced internally by the human body or not: essential and non-essential amino acids (hyperphysics.phy-astr.gsu.edu, 2012).

An essential amino acid (indispensable amino acid) is an amino acid which an organism needs to ingest because it is necessary for nutrition and cannot be synthesized in the body. Since the body is incapable of producing them, they should be provided by means of food and amino acid supplements (www.about.com, 2012).

There are eight essential amino acids listed with their corresponding symbols, abbreviation, pathways etc.:

|Essential Amino Acids |(Body cannot make these amino acids, they must come from food or amino acid supplements.)

Source: www.vaughns-1-1pagers.com, 2012

Non-essential amino acids are those that can be synthesized by the body and therefore it is not necessary for the body to attain them from an outside source like dietary and amino acid supplements (www.fitday.com, 2012). There are ten non-essential amino acids listed with their corresponding symbols, abbreviation, pathways etc.:

Non-Essential Amino Acids (The body can make these amino acids from the above essential amino acids.)

Source: www.vaughns-1-1pagers.com, 2012

|Other Amino Acid Factors

Source: www.vaughns-1-1pagers.com, 2012

2. Which is stronger, α-carboxyl glycine with pKa = 2.4 or α-amino glycine with pKa = 9.8?

pKa is the negative base-10 logarithm of the acid dissociation constant of a solution or pKa = -log10Ka. The lower the pKa value and thus the higher the Ka value, the stronger the acid is (www.about.com, 2012).

From the pKa values, the α-carboxyl portion of the amino acid glycine is the stronger acid since its pKa value is lower than that of the α-amino portion of glycine. Solving for the Ka values,

Ka = 10 –pKa = 10 -2.4 = 3.9811 x 10 -3

Ka = 10 –pKa = 10 -9.8 = 1.5849 x 10 -10

Ka for α-carboxyl portion is higher than that of the α-amino portion, another proof that the former is the stronger acid.