Cell Cycle Regulation, Differentiation, and Apoptosis

Cellular Differentiation

The biological process by which an unspecialized or pluripotent cell ceases dividing to acquire a distinct, specialized structure and physiological function.

$G_0$ Phase

A quiescent or terminal non-dividing state entered by fully differentiated cells exiting the active cell cycle.

Apoptosis

An evolutionarily conserved, genetically controlled mechanism of programmed cell death characterized by cell shrinkage, blebbing, and clearance without triggering an inflammatory response.

Necrosis

Accidental, unregulated cell death resulting from acute trauma, characterized by cell swelling, lysis, and harmful inflammation.

Cyclins

Positive regulatory proteins whose intracellular concentrations fluctuate cyclically across specific phases of the cell cycle.

Cyclin-Dependent Kinases (CDKs)

Serine/threonine kinases whose catalytic activity requires binding to corresponding cyclin partners to phosphorylate downstream targets and advance the cell cycle.

$p53$

A critical tumor suppressor transcription factor activated in response to DNA damage that induces cell cycle arrest for repair or triggers apoptosis if damage is irreparable.

Retinoblastoma Protein ($pRb$)

A negative cell cycle regulator and tumor suppressor protein that acts as a molecular brake to halt cell cycle progression at critical checkpoints.

Interphase

The non-dividing phase comprising $G_1$, $S$, and $G_2$ stages, during which the cell grows, synthesizes proteins, and duplicates its genome.

Cytokinesis

The final physical division of the cytoplasm and plasma membrane, mediated by an actin-myosin contractile ring in animal cells, producing two genetically identical daughter cells.