Which statement regarding bax and bak, two members of the bcl-2 family, is true?
a. bax and bak directly activate caspase-9.
b. bax and bak act as ligands to the apoptosome in activation caspases.
c. bax and bak are antiapoptotic proteins that function to repress apoptosis in cells.
d. when activated, bax and bak form oligomers in the outer membrane of mitochondria, leading to the release of cytochrome c.

Option D When activated, Bax and Bak form oligomers in the outer membrane of mitochondria, leading to the release of cytochrome c.

Explanation:

The proapoptotic genes are involved in the process of apoptosis. The antiapoptotic gene prevents apoptosis that is cell death. The proapoptotic genes are bax, bak, bad and bid. The bcl family genes are antiapoptotic genes. The process involved activation of apoptosis inside the cell is called intrinsic pathway of apoptosis.

The activation proapoptotic genes, Bax and Bak form oligomers in the mitochondria outer membrane. These pores in the mitochondrial membrane allows the release of cytochrome-c that further attaches with Apaf-1. This leads to activation of caspase 9 that further activates caspase 3, thus inducing apoptosis.