Cyclin concentrations rise and fall to activate cyclin-dependent kinases. CDK–cyclin complexes help control cell-cycle checkpoints and entry into mitosis.
Explain how the cell cycle is controlled.
a. cell cycle is a sequence of stages / cell cycle is G1, S,G2 and mitosis
b. (control of the cell cycle) by cyclins/cyclin
c. levels of cyclins rise (and fall)/fluctuate during the cell cycle/surge at different times/have to reach a certain concentration
d. conditions inside as well as outside the cell affect regulation
e. four cyclins/different cyclins to enter different stages of/events in the cell cycle / cyclins regulate the sequence/timing of the cell cycle/cyclins trigger the next stages
f. cyclin-dependent kinases / cyclins bind to kinases and activate them
g. kinases phosphorylate other proteins
h. phosphorylated proteins perform specific functions in the cell cycle