What are the differences between D and L glucopyranose? I have just studied the concept of cyclotron in carbohydrates. My reference book used Glucose as an example and began by saying we can find D-glucose or L-glucose:



Depending on what enantiomer we have, we will get opposite chair conformations at cyclisation:



After saying this, my book states that significant differences appear at cyclisation of these enantiomers, and there I just do not follow. The only difference I see is that one is the mirror image of the other. But visually, I see both structures identically equal. 

Could someone explain to me what differences I should be observing in both chair conformations, and also, what consequences these have on the molecules' behaviors?
They are mirror images of one another and therefore their chemical and physical properties are the same, except for the deflection of polarized light, which will be in opposite directions. 

Mirror image compounds that are not the same are called enantiomers and it does not matter if they are in the open or cyclic form. 
They will, however, have different properties if they are in a chiral medium. 
For instance, if placed in a chiral solvent, they will have different solubilities. 
Chiral means that the compound has a mirror image that can not be superimposed on the original structure.