Sixty percent of the wood of a tree is cellulose—by far the most important ingredient. The structure of cellulose is well understood and is rather simple: Molecules of dextrose are linked in pairs to form a more complex sugar, cellobiose, and these units are hooked up to form long chains of cellulose molecules. This structure of cellulose may be easily changed by action of even a weak acid; cellulose then falls apart into the original dextrose molecules, providing an enormous source of sugar that can be used for many purposes.
