There are two principal methods by which the cells control proper proportions and proper quantities of different cellular constituents:
- The mechanism of genetic regulation.
- The mechanism of enzyme regulation.
The genes can be either activated or inhibited. Most often, these regulatory mechanisms function as feed back control systems that continually monitor the cell's biochemical composition and make corrections as needed. But, on occasion, substances from without the cell (especially some of the hormones) also control the intracellular biochemical reaction by activating or inhibiting one or more of the intracellular control systems.