City Hall functions like a nucleus because it's the center and middle of Los Angeles, California. Like the nucleus, it functions as the center and most important part. City Hall controls all the activities in the city just like the nucleus controls all the activities in a cell.
Like a cell membrane, city limits act as a protection barrier. City limits control what goes in and out of a city like a cell membrane controls the substances that enter and leave a cell.
Like the mitochondria, the Los Angeles power company produces energy. Both the mitochondria and the LA power company are in charge of electricity and energy.
A city wall is like a cell wall because one helps protect the interior of the cell while the other protects people inside the city. They both are used as protection.