Let's pretend that some students demonstrated the carbon cycle by observing
the reaction of yeast to sugar and salt. While salt (NaCl2) was not found to be
a food for yeast, sugar (C12H22O11) was. The resulting process is called
fermentation, in which the yeast took in sugar and oxygen to yield carbon
dioxide and alcohol.
In the experiment described above, what was the source of carbon dioxide
being released by yeast?
