Starch contains glucose monomers in linear forms as well as branched forms. What is the monomer of starch?

• A. Fructose
• B. Glucose
• C. Galactose
• D. Mannose

Answer: (B)

Starch is a plant storage polysaccharide built from glucose units. The glucose monomers link together to form both the mainly linear chains of amylose and the branched chains of amylopectin, so the fundamental building block of starch is glucose. The other sugars listed are monosaccharides that appear in different contexts (fructose in sucrose, galactose in lactose, mannose in certain cell-wall components) and are not the monomer used to construct starch.