# DBT JRF 2020 — Question 145

Exam: DBT JRF 2020 · Section: B · Topic: Cell Biology · Difficulty: Easy

## Question

The following cellular process involves formation of double membrane vesicles that engulf and degrade the cellular organelles and macromolecules

## Options

- **A.** Necrosis
- **B.** Apoptosis
- **C.** Autophagy
- **D.** Macro pinocytosis

## Answer

Option C

## Explanation

Autophagy ('self-eating') is a lysosomal degradation pathway for cytoplasmic components including damaged organelles (mitophagy, reticulophagy), protein aggregates, and intracellular pathogens. Key feature: the formation of a DOUBLE-MEMBRANE structure (the phagophore/isolation membrane) that elongates and sequesters cargo, forming the AUTOPHAGOSOME (double-membrane vesicle). The autophagosome then fuses with lysosomes to form autolysosomes, where lysosomal enzymes (acid hydrolases) degrade the contents. Signals inducing autophagy: nutrient starvation (mTORC1 inhibition), hypoxia, ER stress, pathogen invasion. Necrosis — unregulated cell death (no vesicle). Apoptosis — programmed cell death by caspases, forms apoptotic bodies (single-membrane blebs). Macropinocytosis — large-scale actin-driven plasma membrane ruffling engulfing extracellular fluid; single-membrane macropinosomes.

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