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. Compartmentation divides labor, which increases efficiency of the cell. Hormonal regulation occurs with two responses gene expression and synthesis of second messengers which control metabolic rate. Before learning of the interdependent pathways of metabolism, metabolic control analysis was used by finding the flux control coefficient of each enzyme. Due to the interdependence of the different pathways, distributive control of metabolism is now a more accurate term.