In apoptotic permeabilization of membrane occurs in –
**Core Concept**
Apoptosis is a regulated process of programmed cell death, crucial for maintaining tissue homeostasis. Permeabilization of the cell membrane is a key event in the execution phase of apoptosis.
**Why the Correct Answer is Right**
During apoptosis, the mitochondrial outer membrane permeabilization (MOMP) is mediated by the Bcl-2 family proteins, specifically the pro-apoptotic members Bax and Bak. This leads to the release of cytochrome c from the mitochondria into the cytosol, initiating a caspase cascade. The resulting permeabilization of the cell membrane allows for the influx of ions and water, causing cell shrinkage and eventual cell death.
**Why Each Wrong Option is Incorrect**
**Option A:** This is not a specific location or process involved in apoptotic membrane permeabilization.
**Option B:** Endoplasmic reticulum stress is a different cellular stress response that can lead to apoptosis, but it is not the site of membrane permeabilization.
**Option C:** The lysosome is involved in cell digestion and recycling, but it is not the primary site of membrane permeabilization during apoptosis.
**Clinical Pearl / High-Yield Fact**
Bcl-2 family proteins are key regulators of apoptosis, with pro-apoptotic members (Bax, Bak) promoting membrane permeabilization and anti-apoptotic members (Bcl-2, Bcl-xL) inhibiting it.
**Correct Answer:** B. Mitochondria