Even though starch and cellulose are made up of the same repeating units of glucose, they are very different in their properties. The main difference between starch and cellulose is that

Options

A. cellulose has all its glucose repeats oriented in same direction
B. starch has alternate glucose repeats oriented at 180° to each other
C. starch has all its glucose repeats oriented perpendicular to each other
D. cellulose has alternate glucose repeats oriented at 180° to each other

Answer

**Step-by-Step Solution:**

1. **Understanding the Composition**: Both starch and cellulose are polysaccharides made up of glucose units. However, the way these glucose units are linked together differs significantly.

2. **Types of Glycosidic Bonds**: The main difference lies in the type of glycosidic bonds present in each polysaccharide. Starch is composed of α-glucose units linked by α-1,4-glycosidic bonds, while cellulose is made up of β-glucose units linked by β-1,4-glycosidic bonds.

3. **Structural Configuration**: The structural arrangement of these bonds leads to different configurations. Starch tends to form coiled or helical structures, making it more compact and suitable for energy storage. In contrast, cellulose has a linear structure that allows it to form strong fibers.

4. **Orientation of Glucose Units**: In starch, the glucose units are oriented in the same direction, which contributes to its helical structure. In cellulose, the glucose units are rotated 180 degrees relative to each other, which contributes to its rigidity and strength.

5. **Functional Properties**: Due to these structural differences, starch is digestible by humans and serves as an energy reserve, while cellulose is not digestible by humans and provides structural support in plant cell walls.

**Final Statement**: The main difference between starch and cellulose is that starch consists of α-glucose units linked by α-glycosidic bonds, forming helical structures, while cellulose consists of β-glucose units linked by β-glycosidic bonds, forming straight chains that provide structural support.

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