Final answer:
The statement that cyclins help regulate the cell cycle is true. These proteins, in complex with cyclin-dependent kinases, are crucial for the progression through different phases of the cell cycle, with their levels fluctuating in response to various signals.
Step-by-step explanation:
It is true that proteins called cyclins help regulate the cell cycle. Cyclins, along with cyclin-dependent kinases (Cdks), are vital in the positive regulation of the cell cycle. The concentrations of these cyclin proteins vary in a predictable pattern, increasing in response to both external and internal signals, which allows the cell to progress through various checkpoints. After the cell transitions to a new phase, the cyclins from the prior phase are broken down. The complexes formed by cyclins and Cdks are essential for cell cycle progression. For full activation, these complexes must be phosphorylated, which is a necessary step in advancing the cell to the next phase. Such intricate regulation is crucial to prevent errors that can lead to uncontrolled cell division and potentially, cancer.