Some statements regarding the process of autophagy are given below:
- Autophagy occurs when cells contain aggregated proteins
- Autophagosomes fuse with any organelles
- Autophagosome is a single membrane structure
- Autophagosomes fuse with lysosomes to form autophagolysosomes
Which one of the following combinations of the above statements is correct?
- A and B
- B and C
- C and D
- D and A
Rephrasing the Question:
What is the mechanism of autophagy?
Autophagy can occur when cells contain aggregated proteins, and autophagosomes fuse with lysosomes to form autophagolysosomes (option 4).
Autophagy is the evolutionarily-conserved, regulated mechanism that a cell uses to remove unnecessary or dysfunctional components. It allows the cell to break down and recycle organelles or other cellular components in an orderly fashion.
Autophagy can be caused by multiple things:
- Homeostasis: regulating the number and health of organelles.
- Starvation: In situations of nutrient starvation, autophagy allows cells to recycle unneeded proteins so that they can maintain energy levels to survive.
- Repair: Autophagy degrades damaged organelles, cell membranes and proteins. This includes aggregated and misfolded proteins, especially since these can be resistant to other, more common forms of degradation (like ubiquination).
Autophagy can be divided in categories based on what you’re recycling and how. The most studied form is macroautophagy, in which cytoplasmic components (like organelles) are targeted and enveloped in a double-membraned vesicle known as an autophagosome. This later fuses with a lysosome, to create an autophagolysosome (also known as an autolysosome), and components inside it are then degraded and recycled.