Question

Which of the following describes cyclin-dependent kinase (Cdk)?
A. Cdk is inactive in the presence of cyclin
B. Cdk is present throughout the cell cycle
C. Cdk is an enzyme that attaches phosphate groups to other proteins

• A. A and B Only
• B. B Only
• C. B and C Only
• D. C Only

Hint:

Cdk levels = Constant. Cyclin levels = Fluctuating. Cdk + Cyclin = Active Kinase.

Answer 1

The Correct Option is C

Step 1: Concept
Cdks are key regulatory proteins that control the progression of the cell cycle.

Step 2: Meaning
Their activity is dependent on binding to regulatory proteins called cyclins.

Step 3: Analysis
Statement A is false because Cdks are activated (not inactivated) by the presence of cyclin. Statement B is true: Cdk protein levels remain relatively constant throughout the cycle. Statement C is true: Cdks are kinases, which means they function by phosphorylating (adding phosphate groups to) target proteins.

Step 4: Conclusion
Statements B and C accurately describe the nature and function of Cdks. Final Answer: (C)