Plant cell, the basic unit of all plants. Plant cells, like animal cells, are eukaryotic, which means they have a nucleus and organelles bound to the membrane. The following is a brief overview of some of the main characteristics of plant cells. For a more in-depth discussion of cells, see cell.
Unlike animal cells, plant cells have a cell wall that surrounds the cell membrane. Although it is often perceived as an inactive product that serves primarily mechanical and structural purposes, the cell wall actually has a multitude of functions that plant life depends on. Plant cell walls are composed of cellulose, which differentiates them from other organisms with cell walls, such as bacteria (peptidoglycan) and fungi (chitin). The cell walls of algae are similar to those of plants and many contain specific polysaccharides that are useful for taxonomy.
Plant cells can be distinguished from most other cells by the presence of chloroplasts, which are also found in certain algae. A chloroplast is a type of plastid (a sac-shaped organelle with a double membrane) that serves as a site for photosynthesis, the process by which energy from the Sun is converted into chemical energy for growth. Chloroplasts contain the pigment chlorophyll to absorb light energy. In plants, these essential organelles are found in all green tissues, although they are particularly concentrated in the parenchyma cells of the leaves.