[Campbell Biology P.280] Which of the following statements correctly describes a mechanism o... | Practice Question

Which of the following statements correctly describes a mechanism or key component involved in the initiation of apoptosis as described in the text?

  • A: Apoptosis can only be triggered by external signals, such as death-signaling ligands binding to cell-surface receptors.
  • B: The mitochondrial pathway is always involved in the activation of caspases during apoptosis.
  • C: Proteins like Ced-3, Ced-4, and Ced-9 are involved in relaying the apoptotic signal in both nematodes and mammals.
  • D: DNA damage and excessive protein misfolding primarily trigger apoptosis by activating cell-surface receptors.

Explanation

The text states that Ced-3, Ced-4, and Ced-9 proteins in mammals are similar to those in nematodes and are involved in relaying the apoptotic signal. It also clarifies that apoptosis can be triggered by external signals like death-signaling ligands or internal signals DNA damage from the nucleus, protein misfolding from the ER , meaning option A and D are incorrect. Option B is incorrect because external signals can activate caspases without involving the mitochondrial pathway.