One could analogize the parts of a plant cell being similar to fortified city, with a wall around it, for starters. The cell wall would be there to provide strength and structure to the cell. The cell membrane would be like an interior wall, there for strcture and protection as well. Substances would be able to go selectively back and forth across this wall and membrane, much the same as entrances to the city are controlled by gates and doors. Inside the cell, the nucleus contains all the cells instructions, and serves as the nerve center for the cell; this could be the city hall that governs the actions of the town. The chloroplast produces the energy for the cell, this could be the power plant of the town. There are also mitochondria that help with power production. The endoplasmic reticulum is responsible for directing materials throughout the cell, this could be the transportation department. The vacuole is used for water storage, this could be the water department. The lysozomes are responsible for eliminating waste, this could be the trash, or sanitation department. The Golgi complex is responsible for wrapping and delivery of nutrients and waste products, this could be the post office.