Hormones that deliver a signal to the plasma membrane of target cells are known as

A) cyclins.
B) internal and external signals.
C) growth factors.
D) checkpoints.
E) proto-oncogenes.

Growth Factors

Naturally occurring proteins capable of stimulating cellular growth, proliferation, and cellular differentiation.

Plasma Membrane

A lipid bilayer that encloses the cytoplasm of a cell, protecting it and controlling the movement of substances in and out of the cell.