Nucleotides consist of a nucleobase, a sugar (ribose or deoxyribose) and a phosphate group. Several nucleotides link together make long chains of nucleotides called polynucleotides which can then form nucleic acids like DNA (deoxyribonucleic acid) or RNA (ribonucleic acid), the essential building blocks for all living organisms on earth. In DNA, there are four nucleobases: guanine, adenine, cytosine, and thymine. In RNA, thymine is replaced by uracil (Becker & Kleinsmith, 2009).

In terms of umami, the nucleotides inosinate (IMP), guanylate (GMP) and adenylate (AMP) made respectively from inosinic acid, guanylic acid, and adenylic acid are especially important. These so called 5'-ribonucleotides can interact synergistically with glutamate to enhance the umami experience. These mixtures can frequently be found in yeast extract (Mouritsen & Styrbæk, 2014).