Metabolic steady state
Metabolic steady state is condition of cell in which concentrations of the metabolites inside the cell do not change over time. In cells that are growing exponentially, such as microbes in their log phase of growth, the cells are in metabolic pseudo-steady state as the concentration of metabolites inside the cells in bulk, remain constant on average. Although it might be difficult for you to accept this but we can actually do experiments to study metabolism assuming this metabolic steady state and generate data that would be observed only when this condition was true.