ABSTRACT
B. Proteins have both structural and functional roles. The nucleic acids DNA and RNA are polymers of nucleotides, which themselves consist of a nitrogenous base, a pentose sugar and phosphoric acid. Their structures are detailed in Section C. There are three main types of cellular RNA: messenger RNA (mRNA), ribosomal RNA (rRNA) and transfer RNA (tRNA). Nucleic acids are involved in the storage and processing of genetic information (see Topic D5), but the expression of this information requires proteins.
