What is an alpha and beta linkage in sugars?

The binding of sugars are called glycosidic bonds. These bonds are covalent bonds which, by definition, surround the anomeric carbon of a monosaccharide. Contrary to popular belief, the glycosidic bond does not necessarily have to be between two monosaccharides, just think about what happens in nucleotides, for example, where ribose establishes a glycosidic bond with the nitrogen base. Of course, it can also involve two monosaccharides, as is the case with bonds in oligosaccharides or polysaccharides, but this is not required to happen.

When a glycosidic bond is established, a water molecule is released and is therefore a condensation reaction. The oxygen atom and one hydrogen are released from the anomeric carbon, while the second hydrogen atom is released from the atom to which the anomeric carbon will bind.

Glycosidic bonds are also called alpha or beta bonds. This nomenclature depends on the configuration of the anomeric carbon involved in the glycosidic bond. That is, if the anomeric carbon is in the alpha configuration, the bond is of the alpha type, if it is in the beta configuration, the bond is of the beta type.

For greater understanding, please note the image below.

organisms that lack symmetry are called asymmetrical and belong to phylum porifera/sponges.

organisms with specialized stinging cells belong to phylum cnidaria. stinging cells are called cnidoblast cells.

cnidarians show two morphological forms : polyp (sessile) and medusa (mobile)

filter feeding is observed in porifera members.  

alternation of generation is observed in coelenterata or cnidaria. there is alternation of asexual polyp form and sexual medusoid form. it is also referred as metagenesis.