Cell walls are a structure that are found in plants and it's the outermost structure surrounding a plant cell. One of the jobs of a cell wall is to maintain the shape of the cell. In plant cells, cell walls are filled with cellulose. And cellulose is a rigid structure that provides protection for the cell from the external environment. Not only is the cell wall in a plant protecting the cell from the external environment, it's also holding the structure of the internal environment. Cells tend to contain a lot of water. And so what this cell wall does is it's kind of like a container to hold all the contents of the plant cell in.