Final answer:
Kinases are regulatory enzymes that transfer phosphate groups from ATP to other molecules, while cyclin-dependent kinases (CDKs) specifically need to bind with cyclin proteins to activate and regulate the cell cycle's checkpoints.
Step-by-step explanation:
Definition of Kinases and Cyclin-Dependent Kinases
Kinases are enzymes that catalyze the transfer of a phosphate group from ATP to another molecule within a cell, operating as regulatory switches for various cellular functions.
Specifically, cyclin-dependent kinases (CDKs) are a type of kinase that require binding to a cyclin protein to become fully active. This activation enables CDKs to phosphorylate other proteins, causing changes in their shape and function, which is essential for progression through the cell cycle checkpoints.
The levels of CDK proteins remain relatively stable, but the concentration of cyclin proteins fluctuates, dictating the formation of the CDK/cyclin complexes, which are crucial for the regulation of the cycle at specific points.