Final answer:
Cytochrome c is retained within the mitochondria due to its role in the electron transport chain. It is a peripheral membrane protein that can exist in both membrane-bound and unbound states. In the cytosol, cytochrome c binds to adaptor proteins and activates caspases.
Step-by-step explanation:
Cytochrome c is normally retained within the mitochondria due to its role as an important component of the electron transport chain in cellular respiration. It is a peripheral membrane protein, meaning it is only loosely bound to the cristal membrane of the mitochondrion. Cytochrome c exists in equilibrium between membrane-bound and unbound states, allowing some molecules to exit the intermembrane space while others detach from the cristal membrane and follow. In the cytosol, cytochrome c binds to adaptor proteins that aggregate and activate caspases, which are enzymes responsible for initiating cell digestion.