Module 9: Figure cell cycle
Operation of the growth factor and cell cycle signalling system during different phases of the cell cycle.
Growth factor signalling (red arrows) operates primarily during G1 to drive the cell towards the restriction (R) point, after which control moves over towards the internal cell cycle signalling system (blue arrows). The different cyclin proteins, which are a central feature of the cell cycle signalling system, operate at different points during the cell cycle (Module 9: Figure cell cycle dynamics). Note how the cell grows in size over the course of the cell cycle.