Final answer:
The statement is false. CDKs are enzymes, not regulatory subunits. Cyclins are the regulatory subunits that bind with CDKs to form complexes which regulate the cell cycle.
Step-by-step explanation:
The statement "The regulatory subunits of the complexes are known as CDKs" is false. Cyclin-dependent kinases (CDKs) are not regulatory subunits but enzymes that when bound to cyclins, form CDK/cyclin complexes that regulate the cell cycle. The regulatory subunits referred to are actually cyclins. Cyclins are regulatory proteins whose concentrations fluctuate throughout the cell cycle, determining when the CDK/cyclin complexes form. The CDK proteins, while stable in concentration, require binding with cyclins and phosphorylation at specific sites to be fully active.
These complexes then phosphorylate other proteins, which are necessary to advance the cell to the next phase of the cell cycle. Different cyclins pair with CDKs at specific points in the cell cycle to regulate different checkpoints.