Final answer:
Bcl2 prevents the activation of proapoptotic proteins Bak and Bax in the intrinsic pathway of apoptosis, inhibiting the release of cytochrome C and the subsequent activation of caspases, which are critical for cell death.
Step-by-step explanation:
In the intrinsic pathway of apoptosis, Bcl2 prevents the activation of proapoptotic proteins Bak and Bax on the surface of the mitochondria, not the cell surface. These proteins are part of the Bcl2 family of proteins that regulate apoptosis. When activated, Bak and Bax form channels in the outer mitochondrial membrane, allowing the release of cytochrome C into the cytoplasm. This release triggers a cascade of events including the activation of caspases, which are proteolytic enzymes that are key executioners of apoptosis. By preventing the activation of Bak and Bax, Bcl2 thereby maintains cellular survival by inhibiting the release of cytochrome C, avoiding the cascade that leads to programmed cell death.