Chemistry · Ch 14 — Biomolecules
Biological Functions of Nucleic Acids
Biological Functions of Nucleic Acids
In addition to their well-known role as the structural subunits of the nucleic acids, nucleotides carry out a variety of other, independent functions in every cell. (i) As energy carriers: adenosine triphosphate (ATP) is a nucleotide -- built from the base adenine, the sugar ribose, and a chain of phosphate groups -- that cells use as their universal, immediately-usable unit of chemical energy. (ii) As components of enzyme cofactors: nucleotide-derived cofactors such as coenzyme A, NAD⁺ and FAD are essential partners for many enzymes, shuttling chemical groups or electrons in and out of the reactions those enzymes catalyse; coenzyme A itself is built by joining pantothenic acid (vitamin B5, §14.4.1), a mercaptoethylamine unit, and 3'-phosphoadenosine diphosphate. (iii) As chemical messengers: cyclic AMP (adenosine 3',5'-cyclic monophosphate, cAMP) is a small, ring-closed n …
What this figure shows. The structure of adenosine triphosphate, drawn as the nitrogenous base adenine attached to the 1' carbon of a ribose sugar, with a chain of phosphate groups (the source of ATP's usable chemical energy) attached at the ribose's 5' …
What this figure shows. The full structure of coenzyme A drawn as three joined blocks: a mercaptoethylamine unit at one end (carrying the reactive -SH/thiol group that does coenzyme A's actual chemical work), a pantothenic acid (vitamin B5) unit in the middle, and a 3'-phosphoadenosine diphosphate unit at the other end (an ATP-like adenine-ribose-phosphate group that …
What this figure shows. The structure of adenosine 3',5'-cyclic monophosphate (cyclic AMP): the base adenine attached to a ribose sugar whose 3' and 5' oxygens are both bridged by a single phosphate group, closing the phosphate into a ring -- the cyclic phosphate diester that distinguishes cAMP from ordinary, open-chain AMP and gives it its sign …