Final answer:
Cytochrome C is released from the mitochondria during apoptosis and initiates the formation of a complex that activates caspases to start cellular auto-digestion.
Step-by-step explanation:
In the mitochondrial (intrinsic) pathway of apoptosis, cytochrome C plays a crucial role. When apoptotic signals are present, cytochrome C is released from the mitochondria into the cytosol. It becomes a part of a larger complex by binding with adaptor proteins which in turn attracts procaspases. The binding of procaspase to the cytochrome C-adaptor complex triggers an allosteric change that converts procaspase to an active caspase, the enzyme responsible for initiating the auto-digestion of the cell, which is a hallmark of apoptosis. Caspases disassemble the cellular components, leading to the orderly death and removal of the cell.