The Cell - a teeming mini-workshop

In the cell, proteins are being built up and broken down all the time. For everything to function optimally, the cell also has an integral checkpoint where the composition of various proteins is controlled. Unlike in the spontaneous protein breakdown that food undergoes in our intestines, breaking down proteins inside cells requires energy. This was long a research mystery. Thanks to this year's Nobel Laureates, however, we know that this form of breakdown is an extremely detailed control process in which the protein to be destroyed is marked with a special "label". This happens through a series of chemical reactions, as shown below.