Compounds of C, H, O, P and N. Are macromolecules, polymers composed of repeating monomers called nucleotides linked by phosphodiester links. Form, so long strings or polynucleotide, which makes some of these molecules make it to giant size (millions of nucleotides long). In nature there are 2 types:
1. DNA, is double-stranded, composed of two chains linked together polinucleotídiques throughout its length. This may have double-stranded linear fit (DNA nucleus of eukaryotic cells) or circular (DNA procariòtiques cells and mitochondria and chloroplasts of eukaryotic). The DNA molecule carries the information needed to develop the biological characteristics of an individual and contains messages and instructions so that the cells carry out their functions. Exceptionally, the DNA of some viruses is monocatenary, ie consists of a single polynucleotide without complementary chain.
2. RNA differs from DNA in that the constituents of the nucleotides pentose is ribose instead of desoxirribosa, and instead of the four bases A, G, C, T appears A, G, C, U (uracil instead thymine). RNA chains are shorter than those of DNA, but this feature is due to biological considerations, as there is no limitation to form chemical RNA chains as long as the DNA phosphodiester bond to be chemically identical. The RNA is usually monocateari.