Composition and Functions of Nucliec Acids

Nucleic Acids 
Nucleic acids (nu-kla'ik as'idz) are huge biomolecules with very specific functions in cells. Genes, the hereditary factors that we receive from our parents and that control the characteristics of the cell and organism, are composed of a nucleic acid called DNA (deoxyribonucleic acid) (de­ok'sf-ri"bo-nu-kla"ik as'id). DNA is a molecule that stores coded information. Another important nucleic acid-RNA (ribonucleic acid)-works in conjunction with DNA to bring about protein synthesis in cells.
Both DNA and RNA are polymers of nucleotides joined together. Every nucleotide is a molecular complex of three types of unit molecules: a phosphate, a 5-carbon sugar, and a nitrogen base. The sugar in DNA is deoxyribose, while that in RNA is ribose, which accounts for the difference in their names. The nitrogen bases in DNA are adenine (A), guanine (G), thymine (T), and cytoine (C). The bases in RNA are the same, except that uracil (U) is substituted for thymine.
When nucleotides join together, they form a linear molecule called a strand, composed of a sugar-phosphate backbone, with the nitrogen bases projecting to one side. RNA is single-stranded, but DNA is double-
tranded. The two strands of DNA are twisted in the form of a double helix and are held together by hydrogen bonds between the bases. An unwound DNA helix re­embles a ladder: The steps of the ladder are the hydrogen­bonded nitrogen bases.
The sequence of nitrogen bases in DNA serves as a code for directing the sequence of bases in RNA and then the sequence of amino acids in a protein. In other words, the genes we inheri t determine the types of proteins we can produce in our cells.
Both DNA and RNA are polymers of nucleotides; only DNA is double-stranded. DNA makes up the genes. and along with RNA. controls protein synthesis.

Posted in Human Anatomy and Physiology