Proteasomes are organelles that contain proteolytic enzymes and primarily function to ...

• A. Synthesize proteins
• B. Break down lipids
• C. Remove and recycle damaged proteins from the cytosol
• D. Produce ATP

Answer: (C)

Proteasomes are proteolytic complexes dedicated to protein quality control. They recognize proteins marked with ubiquitin and degrade them into short peptides, recycling the amino acids for new protein synthesis. This cleanup happens mainly in the cytosol (and nucleus) and is essential for removing damaged or misfolded proteins and regulating protein levels. They don’t synthesize proteins, don’t primarily break down lipids, and don’t generate ATP; instead, ATP is used to unfold and feed substrates into the proteolytic chamber. So the main role described—removing and recycling damaged proteins from the cytosol—is exactly what proteasomes do.