Question

Which cell organelle is involved in apoptosis?

• A. Lysosome
• B. Endoplasmic reticulum
• C. Golgi apparatus
• D. Mitochondria

Hint:

The key molecular trigger for mitochondrial-mediated apoptosis is the release of cytochrome c into the cytosol, which acts as a molecular "flare" that activates the caspase cascade.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Apoptosis is a highly regulated process of programmed cell death used to eliminate damaged, senescent, or superfluous cells without triggering inflammation.
It can be initiated via two main pathways: the extrinsic (death receptor) pathway and the intrinsic (mitochondrial) pathway.

Step 2: Detailed Explanation:
The intrinsic pathway of apoptosis is directly controlled by the mitochondria.
Under cellular stress (such as DNA damage, oxidative stress, or absence of survival signals), pro-apoptotic members of the Bcl-2 family (like Bax and Bak) oligomerize to form pores in the outer mitochondrial membrane.
This leads to Mitochondrial Outer Membrane Permeabilization (MOMP).
As a result of MOMP, cytochrome c (which is normally located in the mitochondrial intermembrane space as part of the electron transport chain) is released into the cytosol.
Once in the cytosol, cytochrome c binds to Apaf-1 (apoptotic protease-activating factor 1) and dATP to form a wheel-like heptameric complex called the apoptosome.
The apoptosome recruits and activates procaspase-9 to its active form, caspase-9, which then initiates a cascade of executioner caspases (caspase-3 and caspase-7), leading to the systematic dismantling of the cell.

Step 3: Final Answer:
Thus, the mitochondria are the key organelles regulating the intrinsic apoptotic pathway, corresponding to option (D).