What is the reducing end of a polysaccharide chain?

In a polysaccharide chain (say glycogen), the right end is called the reducing end and the left end is called the non-reducing end. It has branches too. Starch forms helical secondary structures. In fact, starch can hold I2 molecules in the helical portion. The starch-I2 is blue in colour. Cellulose does not contain complex helices and hence cannot hold I2.