|MadSci Network: Cell Biology|
First part: In addition to taking CO2 out of the air, and making O2 from it, plants also require O2 for respiration, just like us. I think the question you are asking is (partially) about the difference between respiration (the use of O2 as the final electron acceptor in the electron transport chain in making energy), and breathing, in the conventional sense. All organisms respire. Some just do it differently from others. For instance, there are any number of anaerobes--those organisms which don't require O2 to survive--in this class. Some examples of this include the bacteria which poplulate our intestines (some of which can also live in the air, like E. coli). Yeast can also survive anaerobically. This occurs during fermentation, in making beer and wine. In this process the yeast make alcohol as the final product of respiration. There are also other 'weird' organisms out there that don't use oxygen, though they tend to populate extremely harsh environments. There are bacteria which live near the deep sea thermal vents that use hydrogen sulfide instead of oxygen for energy production. These first two URLs talk about the electron transport chain http://west.cscwc.pima.edu/~achristensen/etc/sld001.htm http://www.fgi.net/~corpalt/science/etc.htm And these talk about some of those 'weird' organisms. http://www.astrobiology.com/extreme.html#vents http://www.sciam.com/0497issue/0497marrs.html#1 Good luck! -Sarah Tegen
Try the links in the MadSci Library for more information on Cell Biology.