Plant cell showing typical organelles and structures (animal cells are somewhat different). A cell is a complete functional biological unit with many different internal structures. Somewhat like an entire city in miniature. In this diagram, the plant cell is surrounded by a cell wall (in this picture just the primary cell wall is shown; some plant cells build up very thick secondary cell walls internal to their primary walls). The cell wall is traversed at several points by plasmodesmata. Notable, is the large centrally placed vacuole, delimited by the tonoplast. The green discoid structures at the cell periphery are chloroplasts, which conduct photosynthesis. The cell wall, vacuole, plasmodesmata, and chloroplasts distinguish the typical plant cell from the typical animal cell.