Galactan

Part of speech: noun

Definitions

1. A complex carbohydrate built from many galactose sugar units linked together, found in certain seaweeds and plant cell walls
2. A polymer of galactose monomers, a type of polysaccharide that occurs in some algae and in the cell walls of legumes
3. A branched sugar polymer composed chiefly of galactose residues, obtained from red seaweeds and certain plant tissues

Etymology: Galactan is a chemistry coinage rather than a word with a folk history. It is formed from "galact-", the combining form of "galactose", plus the suffix "-an", which chemists use to name polysaccharides built from a given sugar, as in "glucan" and "xylan". So the name simply describes a polymer made of galactose units. Galactose itself takes its name from Greek "gala" (milk), the source of "galactic" and "lactose" as well. The sugar was named for its early association with milk, since lactose, the disaccharide of which it is a part, was the sugar found there. The word "galactose" is a modern scientific coinage, not an ancient one. Galactans occur in plant cell walls and in some seaweeds, where they serve as structural or storage polysaccharides. The chemical naming follows the same pattern across the family of sugar polymers, so a reader who knows "cellulose" and "glycogen" will recognize the logic at once.