Sep 3, 2015

Cell Life Symphony: From Birth to Demise

Within the initial cell of a new multicellular organism lies a set of directives that will not only steer its descendants through cycles of growth, development, and reproduction, but also toward the inevitable conclusion of life. As a facet of this intricate program, numerous cells follow a path of self-termination once they have fulfilled their designated purpose. This process, termed apoptosis (derived from the Greek word for "dropping off" or "falling off"), is initiated by molecular cues that trigger the activation of internally stored self-destruct mechanisms. These mechanisms, akin to stockpiled weaponry, include enzymes specialized in cleaving proteins. Visualize these enzymes as folded pocket knives that, once unfolded, sever structural proteins, including the foundational elements of cytoskeletons and the nucleosomes that arrange DNA.



Ultrastructural features of cell death by apoptosis

The dying cells undergo a sequence of shrinking, condensation, and eventual fragmentation, culminating in the release of small membrane-bound apoptotic bodies. These bodies are typically engulfed and cleared by other cells through a process known as phagocytosis. Importantly, this mode of cell death prevents the uncontrolled release of intracellular components into the extracellular environment, a safeguard against potential harmful effects. In stark contrast, cell death resulting from tissue damage, referred to as necrosis, leads to cell swelling and rupture. This, in turn, releases intracellular contents that can inflict harm on neighboring cells and trigger inflammation.