Alpha and beta glucose differ only in the direction that -H and -OH groups point on carbon 1 (labelled).
The description below assumes that the ring is orientated so that the movement from carbon atom C1 to C6 is in a clockwise direction.
Alpha glucose has an -OH [hydroxyl] group
(red sphere attached to white sphere) that points "downwards"
, away from the ring, whereas the -OH on carbon 1 of beta glucose is above the ring
. This may be seen if the molecules are seen from the edge
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These two forms of glucose are (stereo)isomers, because they contain the same atoms, but they differ in the arrangement of their atoms in space.
They can also be called epimers
because they represent different configurations of atoms about a single stereogenic centre - in this case carbon 1. They can also be called anomers
because they differ only in configuration at the hemiacetal carbon 1, also called the anomeric carbon. This difference is not enough to warrant giving these two forms different names, apart from α-D-glucopyranose and β-D-glucopyranose of course!
This orientation is the reason for the difference between the disaccharides maltose
In maltose there is a (1-4) glycosidic bond formed between one α-glucose and another; in cellobiose a (1-4) glycosidic bond is formed between one β-glucose and another, and this has important consequences for the types of molecules which can be formed as a result of further condensation reactions.
Alpha, 1-4 linkages make starch (amylose and amylopectin) fairly easily broken down by enzymes whereas beta, 1-4 linkages result in linear microfibrils of cellulose which are difficult to break down.