There are two types of nucleic acids:
• Deoxyribonucleic acid (DNA), which serves as a cellular database by storing an immense amount of information about all the polypeptides a cell can potentially make.
• Ribonucleic acid (RNA), which occurs in several different forms (messenger RNA, ribosomal RNA, transfer RNA) and is needed to convert DNA information into polypeptide sequences; in some viruses, RNA serves as the primary database with no DNA involvement; certain RNAs have catalytic ability similar to that of protein enzymes called ribozymes
Nucleic acids are built from subunits called nucleotides. Each nucleotide has three components:
1. a ring-shaped molecule belonging to the class of purine or pyrimidine bases
2. a 5-carbon, or pentose, sugar
3. one or more phosphate groups