Final answer:
Cytochrome C is released from the mitochondrial intermembrane space and initiates a cascade leading to cell apoptosis by converting procaspase into active caspase.
Step-by-step explanation:
Cytochrome C, which initiates a cascade leading to cell apoptosis, is released from the mitochondria. Specifically, it exits from the mitochondrial intermembrane space where it normally functions as part of the electron transport chain. When released into the cytosol, cytochrome C binds to adaptor proteins, which then bind to procaspase, causing it to activate into caspase. This procaspase to caspase conversion begins the process of cellular auto-digestion.