Final answer:
Proteasomes are macromolecular machines involved in protein degradation. They break down damaged or unneeded proteins in the cell. Proteins are tagged with ubiquitin and then degraded by the proteasome.
Step-by-step explanation:
Proteasomes are macromolecular machines involved in protein degradation. They play a crucial role in breaking down proteins that are damaged or no longer needed by the cell. Proteins are tagged with a small protein called ubiquitin, which marks them for degradation by the proteasome. The proteasome then unfolds and cleaves the protein into smaller peptides that can be recycled by the cell.