Question

Why does it not matter whether the OH groups are cis to one another in the furanose ring or trans to one another?

Please help!

Answer 1

I believe it has to do with the mutarotation of the hydroxyl groups in solution.
You can read about furanoses here and mutaroration on the link below that.

http://en.wikipedia.org/wiki/Furanose

http://en.wikipedia.org/wiki/Mutarotation