This reference text provides a link between N-heterocyclic chemistry and biochemistry, enabling a researcher to consult one volume to obtain the structural properties of the N-heterocyclics and the physiological processes in which they take part. N-heterocyclics include molecules of important biological significance, among them the majority of coenzymes, metabolic regulators and integrators such as adenosine and GTP, signalling compounds like the cyclic nucleotides and plant cytokinins, and biochemically functional pigments such as haemoglobin and chlorophyll. In this book the author brings up questions about the role of these components in different metabolic regulations and their biological functions. It should be of use to post-graduate students and researchers in fields such as metabolism, pharmacology, biotechnology, biochemistry, agrochemistry and general chemistry.