Question

How do mitogens stimulate cell cycle entry?

a) Mitogens inhibit cyclin-cdk complexes, preventing cell cycle entry.
b) Mitogens promote the degradation of cyclins, inhibiting cell cycle entry.
c) Mitogens activate cyclin-cdk complexes, facilitating cell cycle entry.
d) Mitogens inhibit DNA replication, preventing cell cycle entry.

Answer 1

Mitogens stimulate cell cycle entry by activating cyclin-cdk complexes, which serve as positive signals to prompt the cell to divide.

Step-by-step explanation:

How do mitogens stimulate cell cycle entry? The correct option is: c) Mitogens activate cyclin-cdk complexes, facilitating cell cycle entry. Mitogens are external factors that promote cell division. They function by signaling the cell to proceed through the cell cycle checkpoints by activating internal molecular signals, particularly cyclin-dependent kinases (Cdks) and cyclin proteins.

The cyclin-Cdk complexes, once activated by phosphorylation, can phosphorylate other substrates that advance the cell cycle. Contrary to inhibitory molecules, which might block the progression until certain conditions are met, mitogens serve as positive regulatory signals to prompt cell cycle entry.