Biochemical pathways and processes
Biochemical processes mediate the interaction of cells with their environment and are responsible for most of the information processing inside the cell. Networks of interacting proteins underlie many of these processes. Three major types of biochemical processes are distinguished: Metabolic pathways are sequences of chemical reactions, each catalyzed by enzymes, where certain product molecules are formed from other small substrates. Metabolites are usually small molecules while enzymes are proteins. Signal transduction networks are pathways of molecular interactions that provide communication between the cell membrane and intracellular end-points, leading to some change in the cell. Signals are transduced by modification of one protein’s activity or location by another protein. Gene regulation circuits determine whether or not a particular gene is expressed at any particular time. Transcription factors, proteins that promote or repress transcription, either directly or indirectly bind regulatory DNA elements. Metabolic, transduction and regulatory circuits are interleaved and integrated. For example, gene regulation circuits are fed by external signals transmitted by signal transduction pathways. The high complexity of these systems makes their proper understanding difficult.
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