Cyclins

Definition

Cyclins are proteins that regulate the progression of the cell cycle by activating cyclin-dependent kinases (CDKs). They ensure that cell cycle events occur in the correct sequence and at the appropriate time.

5 Must Know Facts For Your Next Test

1. Cyclins bind to CDKs, forming a complex that drives the cell through specific stages of the cell cycle.
2. Different types of cyclins are active at different phases of the cell cycle (e.g., G1/S cyclins, S cyclins, M cyclins).
3. The levels of cyclins fluctuate throughout the cell cycle; they are synthesized and degraded as needed.
4. Cyclin-CDK complexes can be regulated by phosphorylation and dephosphorylation events.
5. Dysregulation of cyclin levels can lead to uncontrolled cell division and is often implicated in cancer.

Review Questions

• What role do cyclins play in regulating the cell cycle?
• How do cyclin levels change throughout the cell cycle?
• Why is the regulation of cyclin-CDK complexes important for proper cell division?

Related terms

Cyclin-Dependent Kinases (CDKs): Enzymes that, when activated by binding to a cyclin, drive progression through various stages of the cell cycle.

Cell Cycle Checkpoints: Mechanisms that monitor and verify whether the processes at each phase of the cell cycle have been accurately completed before proceeding to the next phase.

Ubiquitin-Proteasome Pathway: A system responsible for degrading unneeded or damaged proteins, including cyclins, thus regulating their levels within cells.