Nucleotides have many functional roles the first one would be that they
are components of nucleic acids (DNA, RNA), carriers of chemical energy
in the cell (eg., ATP, GTP), components of cofactors (eg., NAD, FAD),
they are also Intermediates in cellular communication and signal
transduction (eg., cAMP, cGMP), and last but not least, donor
substrates for glycobiology (eg. UDPG).
(this multiple choice question has been scrambled)