|MadSci Network: Cell Biology|
Dear Nina, What an excellent question! I had to think about it for a long time to figure out the answer. The most obvious structure that an animal cell has that plant cells do not is centrioles. Centrioles are structures that are important for DNA segregation when a cell undergoes mitosis. Centrioles are associated with the spindle--the filaments that help pull apart the chromosomes. Not a whole lot is understood about centrioles. Here is a website which I thought was useful in this regard. http:// www.cyberenet.net/~aedmills/biorefweb/cells.html Additionally, though both plant and animal cells have vacuoles, and lysosomes, animal cells have many more of each. Plant cells often have one large vacuole while animal cells have many small ones. Lysosomes are an important organelle for digestion of waste materials and food. Animal cells tend to have more of these as well. If you think of plants and animals at an organismal level, there are systems differences--plants don't have nervous systems, immune systems, or muscles, so plants lack nerves, blood cells, and muscle cells. There are other differences too (and this gets somewhat more technical). When you see a plant bend toward the sunlight, this is actually due to new cell growth, rather than repositioning of existing parts (think of bending your elbow to reach the fork on the table). Basically you get more cell growth on the convex side, and that pushes the plant stem toward the light. (Whether this is useful to you or not, I'm not sure, but I thought it was kind of interesting). http:// www.geocities.com/CapeCanaveral/5229/n_1.htm The last differences I want to point out is that animal cells are motile, and plant cells are not. This means there are important differences in structures called the cytoskeleton within the plant and animal cells. Think of the cytoskeleton in animal cells as internal tent poles that you can pretty easily collapse and move around--just like camping. Think of plant cytoskelton as more like the studs that hold up your house--the plant cytoskeleton is more like a foundation for the cell wall. Though you lose flexibility of movement by having a cell wall (just like it's really tough to move a house), you gain a lot of strength to be able to resist the elements, so plants aren't really at a disadvantage because they can't move. http://esg-www.mit.edu:8001/esgbio/cb/cellbasics.html http://biology.clc.uc.edu/courses/bio104/cells.htm http://www.tsba.org/%7Ejudith/tourofcell.htm In the words of my friend Raka (who helped me answer this question): "The general consensus from our lab is that plant cells are way better because they can do everything the animal cells can do and more... :)" Hope this is helpful! Please let me know if I can be of more help. Good luck with AP Bio! -Sarah Admin note: Although higher plants (like flowers, crops, trees) don't have centrioles, green algae such as Chlamydomonas reinhardtii most certainly do, and these are technically counted in the plant kingdom. Chlamydomonas are unicellular algae with cell walls, chloroplasts and centrioles. In fact, a lot of labs use Chlamydomonas to study how centrioles are made and what they do. (So it's not really true that only animal cells have centrioles, but it depends on what you consider a REAL plant).
Try the links in the MadSci Library for more information on Cell Biology.