Nucleotides are more than just the building blocks of nucleic acids. As we will describe in later chapters, there are several nucleotides (or modified nucleotides) with other functions:
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ATP (adenosine triphosphate) acts as an agent of energy transfer in many biochemical reactions (see Key Concept 8.2).
GTP (guanosine triphosphate) serves as an energy source, especially in protein synthesis. It also plays a role in the transfer of information from the environment to cells (see Key Concept 7.2).
cAMP (cyclic adenosine monophosphate) is a special nucleotide with an additional bond between the sugar and the phosphate group. It is essential in many processes, including the actions of hormones and the transmission of information by the nervous system (see Key Concept 7.3).
Nucleotides play roles as carriers in the synthesis and breakdown of carbohydrates and lipids.