How do proteins generally break down? - (Feb/28/2006 )

Lets say a cell makes a unit of protein. How does this protein generally break down? Is it just like radioactive isotopes so that the amount of protein is halfed each unit of time or is there some other model that is usefull to describe general protein breakdown?

Thank you for any help.

The Breakdown of Proteins is very different. If you work with siRNA and want to see the effects on proteine-levels you can take samples after different times and compare on Western Blot...