Question

Three complex carbohydrates that are very important in living things are starch, cellulose, and glycogen (see below).. All three of these polysaccharides are polymers of glucose, yet they behave very differently in our bodies. We can digest starch and glycogen, but not cellulose. Examine the drawing of these three polysaccharides below. What differences can you see between these molecules that might explain why

Answer 1

The functional group highlighted in pink alternates its position on the carbohydrate molecule

Step-by-step explanation:

Complex carbohydrates or polysaccharides are large molecular weight molecules composed of repeating unit of simple carbohydrates which are joined together by covalent bonds known as glycosidic bonds. These glycosidic bonds are foremd between the carbon at position number 1 (known as the anomeric carbon) of one simple carbohydrate and a hydroxyl group of another simple carbohydrate.

The configuration of these linkages determines the properties and functions of the complex carbohydrates. The complex polysaccharides starch, glycogen and cellulose are all composed of glucose monomers linked together by glycosidic bonds.

In storage polysaccharides such as starch and glycogen whose function is to store the simple carbohydrate glucose for when needed by the organism, the glycosidic linkages are said to be in α-linkages, placing the functional groups (CH₂OH) all on the same side.

Even the branching points in glycogen are all in α-linkages. Humans have the enzymes to break these bonds so that starch and glycogen molecules can be metabolized by the body.

In a structural polysaccharide such as cellulose, the glycosidic linkages are β-linkages which results in alternating positions for the functional groups. Since humans do not have the enzymes responsible for the breakage of these linkages, hence, we cannot digest cellulose in our bodies.