Question

The survival, __________________, and size of each cell in an animal are controlled by extracellular signal molecules secreted by neighboring and distant cells. Many of these signal molecules bind to a cell-surface __________________ and trigger various intracellular signaling pathways. One class of signal molecules, called __________________, stimulates cell division by releasing the molecular brakes that keep cells in the __________________ or __________________ phase of the cell cycle. Members of a second class of signal molecules are called __________________, because they stimulate cell growth and an increase in cell mass. The third class of signal molecules, called __________________, inhibits __________________ by regulating members of the __________________ family of proteins. In addition to such stimulatory factors, some signal proteins such as __________________ act negatively on other cells, inhibiting their survival, growth, or proliferation.

anaphase differentiation myostatin

annihilation G₀ nourishment

apoptosis G₁ nutrition

arrestase G₂ phosphatases

Bcl2 growth factors proliferation

biosynthetic interphase receptor

cascades ligand S

caspase M survival factors

Cdk mitogens transcription

cyclin