Amino acids are the building blocks of proteins and thus, are very important for the overall health and survival of an individual. Amino acids can be classified based on a number of different types and classifications. These different types or classifications of amino acids are determined by their specific functional groups and these functional groups gives the amino acids their unique properties such as being polar, aromatic, charged or aliphatic. In this article we will look at the different amino acid functional groups.
What are amino acid functional groups?
As briefly discussed earlier, amino acid functional groups determine the type or class of amino acid present. The molecular structure of these functional groups are usually represented by the placeholder labeled “R”. This specific placeholder serves as an indicator where the functional group will be located. These functional groups are in turn, connected to a carbon atom and to the right and left of this carbon atom, also identified as the backbone of the amino acid, are the carboxylic acid (COOH) and amine group (NH2). This design and structure comprises what is called an amino acid. These amino acids will have their functional groups and their unique properties composed of molecular structures that may be as simple as hydrogen or as large as a circular molecular structure.
Types of “R” or Amino Acid Functional Groups
There are three (3) Major types of Functional Groups based on the R group of the said amino acid. These are:
1. Amino Acids with Nonpolar side chains
These are amino acids or organic compounds that have no “charge” on the R group. Nonpolar amino acids are hydrophobic which means they do not tend to move or combine with other aqueous compounds.
2. Amino Acids with Polar Side Chains
These are amino acids or organic compounds that can identified as either positively or negatively charged. Amino acids that are positively charged tend to be more basic while negatively charged amino acids tend to be more on the acidic side.
3. Amino Acids that have electrically charged side chains
As mentioned earlier, amino acids can generally be either positively charged, negatively charged or neutral/ uncharged. Amino acid side chains can also have a specific charge and those with a positive charge tend to be basic such as arginine, histidine and lysine. Side chains with a negative charge such as aspartic acid and glutamic acid, tend to be acidic.
These three (3) major types of functional groups have a number of amino acids per classification or type. Listed below are the aforementioned amino acids:
Amino Acids with Nonpolar side chains
- Glycine with a three (3) letter code of Gly, single letter code of G and a molecular formula of C2H5NO2
- Alanine with a three (3) letter code of Ala, single letter code of A and a molecular formula of C3H7NO2
- Valine with a three (3) letter code of Val, single letter code of V and a molecular formula of C5H11NO2
- Leucine with a three (3) letter code of Leu, single letter code of L and a molecular formula of C6H13NO2
- Isoleucine with a three (3) letter code of Ile, single letter code of I and a molecular formula of C6H13NO2
- Methionine with a three (3) letter code of Met, single letter code of M and a molecular formula of C5H11NO2S
- Phenylalanine with a three (3) letter code of Phe, single letter code of F and a molecular formula of C9H11NO2
- Tryptophan with a three (3) letter code of Try, single letter code of W and a molecular formula of C11H12N2O2
- Proline with a three (3) letter code of Pro, single letter code of P and a molecular formula of C5H9NO2
Amino Acids with Polar Side Chains
- Serine with a three (3) letter code of Ser, single letter code of S and a molecular formula of C3H7NO3
- Threonine with a three (3) letter code of Thr, single letter code of T and a molecular formula of C4H9NO3
- Cysteine with a three (3) letter code of Cys, single letter code of C and a molecular formula of C3H7NO2S
- Tyrosine with a three (3) letter code of Tyr, single letter code of Y and a molecular formula of C9H11NO3
- Asparagine with a three (3) letter code of Asn , single letter code of N and a molecular formula of C4H8N2O3
- Glutamine with a three (3) letter code of Gln, single letter code of Q and a molecular formula of C5H10N2O3
Amino acids with electrically charged side chains
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Acidic Amino Acids
– Aspartic Acid with a three (3) letter code of Asp, single letter code of D and a molecular formula of C4H7NO4
– Glutamic Acid with a three (3) letter code of Glu, single letter code of E and a molecular formula of C5H9NO4 -
Basic Amino Acids
– Arginine with a three (3) letter code of Arg, single letter code of R and a molecular formula of C6H14N4O2
– Histidine with a three (3) letter code of His, single letter code of H and a molecular formula of C6H9N3O2
– Lysine with a three (3) letter code of Lys, single letter code of K and a molecular formula C6H14N2O2
There are some unique amino acids that do not readily fall under the abovementioned classifications or types of functional groups and these are:
- Glycine with a three (3) letter code of Arg, single letter code of R and a molecular formula of C2H5NO2
- Proline with a three (3) letter code of Arg, single letter code of R and a molecular formula of C5H9NO2
While all these functional groups and molecular formulae can seem too scientific to the ordinary person, the simple truth behind these amino acids is that they are rather powerful organic compounds. When your body takes them correctly and maintains appropriate levels based on your current health status, you can enjoy various health benefits. Amino acids and their functional groups are a must for health and survival.