This chapter on metabolism breaks down the process into two distinct subunits catabolism the degradation of complex structures and anabolism the synthesis of complex organic molecules. The metabolic process can be broken up into three different stages, from stage 1 with complex molecules to stage 3 dealing with simple organic compounds. The Flux is the intracellular reaction rate and the pathways are the specific reaction sequence. Organisms are split between autotrophs, synthesize glucose from CO2, and heterotrophs, synthesize glucose utilizing other organic compounds, humans are heterotrophs, plants are autotrophs. Some microorganisms in anaerobic environments utilize other means for syntheses besides oxidation such as fermentation.
Glycolysis is the degradation of carbohydrates that contribute to the citric acid cycle.
Biosynthesis and degradation occur with separate pathways and are regulated separately. The reaction processes in separate compartments and with allosteric control prevent futile cycles. It is the cleavage of the phosphoanhydride bonds, which produce energy, which then can be coupled with exogenic processes. Enzyme concentrations change in response to different metabolic needs. Control by enzyme activity is reversible ligand interactions and covalent modification of protein molecules.