Questions and Answers
Explain the role of cyclin and cyclin-CDK complexes in controlling the cell cycle.
Cyclin and cyclin-CDK complexes regulate the cell cycle by signaling when the cell is ready to pass from one stage to another through phosphorylation. Cyclins activate cyclin-dependent kinases (CDKs), which then attach phosphate groups to other proteins, triggering their activity and allowing progression to the next phase.
What is the role of cyclin D in the cell cycle?
Cyclin D helps in the progression of the cell through G1 and into the S phase.
Outline the discovery of cyclins including the role of serendipity.
Tim Hunt discovered cyclins while studying embryonic development when he observed a protein that increased and decreased in concentration with each cycle of cell division. This discovery was serendipitous as he was not specifically searching for cyclins.
What is the role of cyclin B in the cell cycle?
Signup and view all the answers
What is the role of cyclin A in the cell cycle?
Signup and view all the answers
What is the role of cyclin E in the cell cycle?
Signup and view all the answers
Study Notes
Role of Cyclin and Cyclin-CDK Complexes
- Cyclin-dependent kinases (Cdks) are enzymes that phosphorylate other molecules, signaling readiness for the next cell cycle phase.
- Activation of Cdks requires binding to cyclins, which are regulatory proteins that undergo cycles of synthesis and degradation.
- Forming a cyclin-CDK complex triggers the cell to progress to the next phase.
- Cyclins must reach a specific threshold to allow progression, indicating the cell's readiness.
- Two classes of cyclins: mitotic cyclins and G1 cyclins, each responsible for different phases of the cell cycle.
Role of Cyclin D
- Cyclin D, also known as G1 cyclin, is crucial for cell progression from the G1 phase to the S phase, initiating DNA synthesis.
Discovery of Cyclins
- Tim Hunt's discovery of cyclins was serendipitous, stemming from his studies on embryonic development where he noted proteins changing concentration across cell division cycles.
- This chance observation led to the identification of cyclins when he was not initially searching for them.
Role of Cyclin B
- Cyclin B, a mitotic cyclin, regulates cell progression from prophase to metaphase, primarily through the control of the mitotic spindle.
- Degradation of Cyclin B is necessary for the cell to enter anaphase, facilitating successful mitosis.
Role of Cyclin A
- Cyclin A is responsible for initiating DNA replication during the S phase and prepares the centrosome for mitosis in the G2 phase.
Role of Cyclin E
- Cyclin E, also known as S cyclin, is essential for preparing DNA for replication, ensuring the cell is ready for the S phase.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Description
This quiz focuses on the role of cyclins and cyclin-CDK complexes in regulating the cell cycle. Learn how these protein interactions signal the cell to progress through different stages by understanding the process of phosphorylation and its significance. Test your knowledge on this critical aspect of cell biology.
