What is the monomer that starch and cellulose are made from?

Starch and cellulose are both polysaccharides formed from chains of glucose molecules, which serve as their monomer units. In the case of starch, glucose units are linked by α-glycosidic bonds, allowing it to function as a storage polysaccharide in plants. On the other hand, cellulose consists of β-glycosidic bonds between glucose units, contributing to the structural integrity of plant cell walls.

Understanding that glucose is a simple sugar (a monosaccharide) helps clarify why it is the correct choice; it is this particular monomer that polymerizes to form both starch and cellulose, despite their different functions and structural properties. The other options listed, such as galactose, fructose, and ribose, represent different monosaccharides that do not form starch or cellulose. Galactose is a component of lactose, fructose is a component of sucrose, and ribose is part of RNA, making them unrelated to the creation of starch and cellulose.