Final answer:
Apoptosis is a mechanism that allows cells to die in a controlled manner. It can be initiated by both external signaling and internal checkpoints. External signaling occurs when cells move away from the extracellular matrix, while internal checkpoints monitor a cell's health for abnormalities.
Step-by-step explanation:
Apoptosis, or programmed cell death, is a mechanism that allows cells to die in a controlled manner. It is initiated when a cell is damaged, superfluous, or potentially dangerous to an organism. Several underlying mechanisms of apoptosis have been discovered.
One mechanism involves external signaling that triggers apoptosis. For example, cells can undergo apoptosis when they move away from the extracellular matrix, a network of glycoproteins that provides structural support. Binding of cellular receptors to the extracellular matrix initiates a signaling cascade within the cell. If the cell moves away, the signaling ceases and apoptosis occurs.
Another mechanism involves internal checkpoints that monitor a cell's health. If abnormalities are observed, a cell can spontaneously initiate apoptosis. Abnormalities can occur due to viral infections, uncontrolled cell division, or other factors.