Apoptosis involves all but which of the following?
(A) fragmentation of the DNA
(B) cell-signaling pathways
(C) lysis of the cell
(D) digestion of cellular contents by scavenger cells
The correct answer and explanation is:
The correct answer is (C) lysis of the cell.
Apoptosis is a form of programmed cell death that is highly regulated and orderly. During apoptosis, several distinct processes occur that ensure the removal of the dying cell without triggering inflammation or damaging surrounding tissues.
- Fragmentation of the DNA (A): One of the hallmark features of apoptosis is the fragmentation of the cell’s DNA. Enzymes like caspases activate endonucleases that break down the DNA into small fragments. This ensures that the genetic material is properly dismantled before the cell is removed.
- Cell-signaling pathways (B): Apoptosis is initiated and controlled by various cell-signaling pathways. These pathways include intrinsic (mitochondria-mediated) and extrinsic (death receptor-mediated) signals. Both pathways activate caspases, which are proteases that orchestrate the breakdown of cellular components.
- Lysis of the cell (C): Unlike necrosis, another form of cell death, apoptosis does not involve lysis (breaking open) of the cell. In necrosis, the cell membrane ruptures, releasing harmful substances into the surrounding tissue, which can cause inflammation. In apoptosis, the cell membrane remains intact until the cell is ultimately phagocytized by neighboring cells or macrophages.
- Digestion of cellular contents by scavenger cells (D): After the cell has undergone apoptosis, the remnants of the cell are cleared by scavenger cells, like macrophages, through phagocytosis. This process prevents the release of intracellular contents that could cause inflammation.
In summary, apoptosis is a controlled process that leads to the breakdown and safe removal of a cell without causing inflammation, in contrast to necrosis, which is more chaotic and often leads to cell lysis.