Which of the following acts as a control of cell division?

• A. Ribosomes
• B. Lysosomes
• C. Mitochondria
• D. Cyclin-dependent kinases (Cdks)

Answer: (D)

Verified step by step guidance

1. Understand the context of the question: The problem is asking about the control of cell division, which is a key process in cell biology. The options provided (Ribosomes, Lysosomes, Mitochondria) are organelles, but the correct answer is a protein complex, Cyclin-dependent kinases (Cdks).
2. Recall the role of Cyclin-dependent kinases (Cdks): Cdks are enzymes that regulate the cell cycle by phosphorylating specific target proteins. They are activated by binding to cyclins, which are regulatory proteins whose levels fluctuate during the cell cycle.
3. Differentiate between the options: Ribosomes are involved in protein synthesis, Lysosomes are responsible for breaking down cellular waste, and Mitochondria are the powerhouse of the cell, generating ATP. None of these organelles directly control cell division.
4. Explain how Cdks control cell division: Cdks ensure that the cell progresses through the different phases of the cell cycle (G1, S, G2, and M phases) in a controlled manner. For example, the G1/S checkpoint is regulated by specific cyclin-Cdk complexes to ensure DNA is undamaged before replication.
5. Summarize the importance of Cdks: Cyclin-dependent kinases are essential for maintaining the proper timing and order of cell cycle events, preventing uncontrolled cell division, which could lead to conditions like cancer.