Cell membranes are structured so that molecules can pass in and out of the cell across them. while both plant and animal cells have membranes, plant cells also have cell walls surrounding their cells. which of the following observations best supports the conclusion that molecules can cross cell walls as well? every cell has its own nucleus. the chloroplasts need light in order to work. the cell wall is directly outside the cell membrane. water from the soil is used in photosynthesis.