Basic Physiology, Body Fluids, Membrane Transport, Nerve and Muscle Function

Nucleic acids

Nucleic acids include the macromolecules DNA and RNA which are important in the genetic regulation of protein production and cellular reproduction. The subunits if these macromolecules are known as nucleotides and consist of a sugar (deoxyribose in the case of DNA and ribose in the case of RNA), a Phosphate group and one of four bases. These four bases are: Adenine, Cystosine, Guanine and Thymine. Thymine is substituted for Uridine in RNA.

In both DNA and RNA, the nucleotides are polymerised in a strand through phospodi-ester bonds between the sugar back-bone. These single strands can form a double stranded molecule through hydrogen bonds between pairs of nucleotides. Guanine and Cytosine can form three hydrogen strands while adenine and thymine (uracil) can form two hydrogen bonds. Thus Guanine always pairs with cytosine and adenine always pairs with thymine. This form the Basis of the primary functions of the nucleic acids.