# How do we assign alpha/beta status in polysaccharides?

In polysachharides like sucrose or any other disachhaharides, how is it that we assign whether the glycosidic bond is alpha/beta ?

For example the images here: http://forums.studentdoctor.net/showthread.php?t=898328 (kindly refer to the images of the original question, both of them)

How does one decide which glycosidic bonding is alpha and which is beta ? What if one of the monosachharides is alpha and one is beta constituting the disachharides ? How do you know that in the final acetal formation which sachharide acted as nucleophile and which acted as electrophile after seeing the disaccharide , take for example sucrose , glucose/sucrose (?) which acted as nucleophile any why ?

In beta you can't form a glycosidic bond; you have to remove a water molecule from the $\beta$-glucose to make a glycosidic bond which is (0). so drawn out alpha and beta the $\ce{-OH}$ in alpha on carbon one points below and on the adjacent carbon points below.