[Campbell Biology P.279] According to the provided text and Figure 11.20, which of the follo... | Practice Question

According to the provided text and Figure 11.20, which of the following statements accurately describes the initial regulatory mechanism of apoptosis in C. elegans in the absence of a death signal?

  • A: Active Ced-9 protein promotes Ced-4 activity, leading to cell death.
  • B: Inactive Ced-9 protein inhibits Ced-4 activity, keeping the cell alive.
  • C: Active Ced-9 protein inhibits Ced-4 activity, preventing apoptosis and keeping the cell alive.
  • D: Ced-3 and Ced-4 are actively degrading cellular components in the absence of a death signal.

Explanation

Figure 11.20a and the accompanying text state that as long as active Ced-9, located in the outer mitochondrial membrane, is present, it inhibits Ced-4 activity, thus preventing apoptosis and ensuring the cell remains alive. Ced-9 acts as a 'brake' on the apoptotic pathway.