In a typical apoptotic cell, the mitochondrial membrane potential decreases, making option (C) the incorrect statement. Apoptosis involves distinct biochemical changes like phosphatidylserine externalization and cytochrome c release, but mitochondrial dysfunction is a hallmark, not an exception. The correct answer is (C) Mitochondrial membrane potential does not change.​

Option Analysis

Phosphatidylserine on outer surface (A): Correct—apoptotic cells flip phosphatidylserine from inner to outer leaflet, signaling phagocytosis; detected early via Annexin V binding.​

Cytochrome c from mitochondria (B): Correct—intrinsic pathway triggers mitochondrial outer membrane permeabilization (MOMP), releasing cytochrome c to form apoptosome and activate caspases.​

Mitochondrial membrane potential unchanged (C): Incorrect—ΔΨm drops due to MOMP, uncoupling oxidative phosphorylation; this drives apoptosis, not stability.​

Annexin-V binds surface (D): Correct—Annexin V specifically binds external phosphatidylserine in calcium-dependent manner, standard apoptosis assay.​

Apoptosis Hallmarks Overview

Apoptosis features cell shrinkage, blebbing, chromatin condensation, DNA laddering, and caspase activation without inflammation. Mitochondria centralize intrinsic pathway via Bax/Bak pores causing potential loss and cytochrome c efflux.​

Apoptosis hallmarks include phosphatidylserine externalization and cytochrome c release, but mitochondrial membrane potential always collapses in typical apoptotic cells—making “does not change” the incorrect statement. This MCQ tests core cell death mechanisms vital for molecular biology, cancer research, and exams like CSIR NET.​

Key Apoptotic Changes

• Phosphatidylserine flip (A): Plasma membrane asymmetry lost; PS exposure marks “eat me” signal.​

• Cytochrome c efflux (B): Mitochondrial trigger activates caspase cascade via apoptosome.​

• ΔΨm drop (C): Potential loss essential; statement denies this hallmark.​

• Annexin-V assay (D): Gold standard for detecting early apoptosis.​

Why Mitochondria Matter

MOMP by Bax/Bak dissipates ΔΨm, halting ATP and releasing pro-apoptotics—undeniable in typical apoptotic cells. Necrosis swells mitochondria; apoptosis shrinks them.​

Exam Tips

Distinguish apoptosis (ordered, non-inflammatory) from necrosis; focus on mitochondrial role over morphology alone.​