megaevelie - 23-11-2011 at 06:44
1. What substance is responsible for giving a positive color reaction with the different tests for sugars?
2. What factors may interfere with producing negative color reactions?
3. What is the physiological importance of knowing the specific
classes of carbohydrates?
I am so lost in finding answers for these questions in our laboratory experiment in analysis of sugars. Please help! 
[Edited on 23/11/2011 by megaevelie]
Ozone - 23-11-2011 at 17:31
Your query is *very* broad, and would require hours of courses and years to understand in any detail. Because I don't have your notes (nor do I want
them), I cannot point out the answers that are no-doubt given within. That said, see http://en.wikipedia.org/wiki/Carbohydrate for an introduction (link out from there).
Any Organic Chemistry text will give the customary week or two on the subject dealing with Fischer's elucidation of glucose, Kiliani syntheses,
periodate cleavage, etc. For more in-depth information, see Pigman, W. (1957), which is my personal favorite.
If you look (search function on this site), you will find that I have already described the Molisch assay (quite general for carbohydrates) last week.
In that thread is mention to at least one other major chromophore/reagent/reaction that you could look up.
Diversity in nature comes from carbohydrates. You have only 4 (5 for RNA) typical bases for DNA, 21 (typical) amino acids (not counting taurine and
felinine, for cats) that can be used to make protein. There are several orders of magnitude-more ways to connect and or modify carbohydrate types.
Antigen labels, glycoproteins, you name it. Gene regulation, yep.
In the simplest case, for almost all living things, you are looking at D sugars and proteins based on L amino acids. Start there.
Good luck,
O3