Question

what are the main growth factors that regulate the check points of the cell cycle? hormones pheromones neurological signals structural proteins

Explanation:

Hormones are chemical messengers that can regulate various biological processes, including the cell cycle checkpoints. Pheromones are used for communication between organisms of the same species, not for regulating cell cycle checkpoints. Neurological signals are related to the nervous system's communication and not directly to cell cycle checkpoints. Structural proteins provide support to cells but do not regulate cell cycle checkpoints.

Answer:

hormones