Final answer:
The G2/M transition is the second regulatory point of cell division, involving the crucial cyclins and cyclin-dependent kinases (Cdks) proteins. It serves as a critical checkpoint before mitosis and is regulated by both positive and negative regulatory molecules.
Step-by-step explanation:
The second regulatory point of cell division is the G2/M transition, where the crucial proteins involved are cyclins and cyclin-dependent kinases (Cdks).
The regulation of the cell cycle is an intricate process involving various checkpoints and proteins that ensure proper cell division. The second regulatory point is located at the G2/M transition, which is pivotal before the cell enters mitosis. This checkpoint is primarily monitored by the levels of specific regulatory proteins known as cyclins, and enzymes called cyclin-dependent kinases (Cdks). These proteins are called positive regulators since they are essential in promoting the cell cycle progression through the checkpoints. Their concentrations fluctuate throughout the cell cycle, increasing to trigger the next phase and then being degraded once their function is completed. Negative regulators also play a role at these checkpoints, with the best understood being the tumor-suppressor proteins: retinoblastoma protein (Rb), p53, and p21, which help prevent uncontrolled cell division and cancer. It is essential to have a balance between positive and negative regulatory molecules to maintain cell cycle control and prevent related diseases.