Final answer:
Cells are most sensitive to antibiotics and disinfectants during the log phase of growth, where they are actively dividing and their metabolic activity is high, making antibiotics that disrupt cell processes effective.
Step-by-step explanation:
Cells are most sensitive to antibiotics and disinfectants during the log phase of their growth. This phase is characterized by constant growth rate and uniform metabolic activity, making bacteria especially susceptible to agents that target protein, DNA, and cell-wall synthesis. Thus, treatments designed to disrupt these processes are most effective during the log phase. However, in the stationary phase and death phase, cells switch to a survival mode and reduce their metabolic activities, or may form endospores, making them less susceptible to such treatments. Various factors, such as the concentration of antimicrobial agent, length of exposure, and the physical state of the cells (e.g., vegetative or endospore form), can influence the effectiveness of antibiotics and disinfectants.