# Anabolic reactions may be characterized as

The rate of turnover in a metabolic pathway, otherwise known as the metabolic flux , is regulated based on the stoichiometric reaction model, the utilization rate of metabolites, and the translocation pace of molecules across the lipid bilayer . [20] The regulation methods are based on experiments involving 13C-labeling , which is then analyzed by Nuclear Magnetic Resonance (NMR) or gas chromatography-mass spectrometry (GC-MS) -derived mass compositions. The aforementioned techniques synthesize a statistical interpretation of mass distribution in proteinogenic amino acids to the catalytic activities of enzymes in a cell. [21]

Thermodynamically unfavorable reactions can be driven by a thermodynamically unfavorable reaction when it is coupled. This is because a pathway must satisfy two criteria: (1.) the individual reactions must be specific and (2.) the entire set of reactions that constitute the pathway must be thermodynamically favored. A reaction that is specific will yield only one particular product or set of products from its reactants due to enzyme specificity. Thermodynamics of metabolism is most readily approached in relation to free energy , which states that a reaction can occur spontaneously only if Δ G {\displaystyle \Delta G} is negative. This is due to the formation of products C and D from subtrates A and B given by the formula