What is a monomer or smaller unit of a carbohydrate?

Answer 1

The carb monomers are the three individual 6-carbon sugars (monosaccharides). The most abundant of these, by far, in nature is glucose. The other two are galactose and fructose.

Starch is a polymer, either branched or unbranched, of glucose. Table sugar, or sucrose, is a glucose linked to a fructose. Maltose is 2 glucoses linked, and lactose is a glucose linked to a galactose. The latter three are disaccharides. Starch is a polysaccharide.

The above constitute almost all the carbs we eat on a daily basis, although we eat very little maltose per se. Rather, the digestion of starch to glucose results in the temporary presence of maltose in our small intestines; but it is quickly broken down to glucose as it is absorbed into the intestinal cells.

Answer 2

Glucose