Cell cycle Control system- Cyclins and CDKs

The cell cycle is regulated by a cell cycle control system that ensures cells divide accurately and at the proper time. The two key components of this system are Cyclins and Cyclin-Dependent Kinases (CDKs). Cyclins are regulatory proteins whose concentration changes during different stages of the cell cycle. Different cyclins are produced at specific phases and then degraded after their function is completed. CDKs are enzymes (protein kinases) that remain present in the cell throughout the cycle but are inactive on their own. When a cyclin binds to its specific CDK, it forms an active Cyclin-CDK complex. This complex phosphorylates target proteins and triggers events required for progression through the cell cycle, such as DNA replication and mitosis. Major Cyclin-CDK Complexes Cyclin D–CDK4/6: Promotes progression through the G1 phase. Cyclin E–CDK2: Initiates the G1 to S phase transition. Cyclin A–CDK2: Regulates DNA replication during the S phase. Cyclin B–CDK1: Triggers entry into mitosis (M phase). Thus, cyclins act as the control switches, while CDKs function as the engines that drive the cell cycle forward, ensuring orderly growth and division of cells. #cellbiology