Cyclin-dependent kinases (CDKs) are a family of enzymes that play a crucial role in regulating the cell cycle. They are activated by binding to specific proteins called cyclins, which help control various phases of cell division. CDKs add phosphate groups to target proteins, influencing their activity and ensuring that the cell progresses through the cycle at the right time. The activity of CDKs is tightly regulated to prevent uncontrolled cell division, which can lead to diseases such as cancer. Different CDKs are involved in different stages of the cell cycle, including CDK1 for mitosis and CDK2 for the transition from the G1 to S phase. This regulation is essential for maintaining proper cellular function and growth.