A proteasome is a complex protein structure found in cells that plays a crucial role in degrading and recycling proteins. It helps maintain cellular health by breaking down damaged, misfolded, or unneeded proteins into smaller peptides. This process is essential for regulating various cellular functions and ensuring that proteins are available for new synthesis. Proteasomes work in conjunction with another cellular mechanism called the ubiquitin system, which tags proteins for degradation. When a protein is marked with ubiquitin, it is directed to the proteasome, where it is unfolded and fed into the core for breakdown. This system is vital for processes like cell cycle regulation and response to stress.