AP BIOLOGY

Detailed explanation-1: -Proteins that respond to events outside the cell are called external regulators. External regulators direct cells to speed up or slow down the cell cycle. Cancer is a disorder in which some of the body’s own cells lose the ability to control growth.

Detailed explanation-2: -Growth factors (GFs) are a group of proteins stimulating the growth of specific tissues. GF plays important roles in the regulation of cell division that drives cell proliferation. Each GF binds to a specific cell–surface receptor.

Detailed explanation-3: -Cyclins, cyclin-dependent kinases (Cdks), and the APC/C.

Detailed explanation-4: -Growth factors-external regulators that stimulate the growth and division of cells.