Elements: C, H, O, and N.
Function: Blueprint for protein synthesis in cells, heredity.
Of the organic molecules, there are fewer nucleic acids, yet they the most unique parts among the organic molecules. Nucleic acids are made from three organic groups, a phosphate group, a pentose sugar, and nitrogen bases. One nucleic acid is bound to another through the phosphate group. Nucleic acids can be divided into two groups, ribonucleic acid (RNA) and deoxyribonucleic acid (DNA).
There are only three differences between these two nucleic acids. First, RNA is made with the pentose sugar ribose, and DNA is made with the pentose sugar deoxyribose. Second, RNA contains the nitrogen base uracil, and DNA contains the nitrogen base thymine. Third, RNA has only one strand of nucleic acids, while DNA is made from a double strand, wrapping around each other in a double helix. Beyond the pentose sugar, nucleic acids differ in the nitrogen base that they contain. The nitrogen bases can be divided into two groups based upon the shape of the nitrogen base, pyrimidines and purines. The pyrimidines have a hexagon shape, generally made with four carbons and two nitrogens. The pyrimidine cytosine has an amine group attached to the first carbon. Both thymine and uracil has an oxygen in place of the amine group. But thymine has a methyl group attached to the second carbon, where uracil does not. The pyrimidines are bonded to the pentose sugar by the nitrogen that lies at the third position, between the CH and C=O, on the hexagon ring.
The purines have a double-ring shape, with a pentagon attached to one side of a hexagon. Adenine , similar to cytosine, has an amine group attached to the first carbon of the hexagon ring. Guanine, similar to thymine and uracil, has an oxygen in place of the amine group. The purines are bonded to the pentose sugar by the nitrogen on the pentagon ring.
On DNA, and when RNA is being made, RNA synthesis, pyrimidines attach to purines by hydrogen bonds between the nitrogens of the purines, as well as the double-bonded oxygen and the nitrogen on the pyrimidine.
It is the arrangement of the nucleic acids on these large genetic molecules that form the genetic code for living organisms.