Cellulose is a straight-chain polysaccharide composed of only:

Options

A. `D-`Glucose units joined by `alpha-`glycosidic linkage.
B. `D-`Glucose units joined by `beta-`glycosidic linkage.
C. `D-`Glucose units joined by `alpha-`glycosidic linkage.
D. `D-`Glucose units joined by `beta-`glycosidic linkage.

Answer

**Step-by-Step Solution:**

1. **Understanding Cellulose**: Cellulose is a type of polysaccharide, which means it is a large molecule made up of many smaller units (monomers) linked together.

2. **Identifying the Monomer**: The monomer that makes up cellulose is D-glucose. This is a simple sugar that serves as the building block for cellulose.

3. **Linkage Type**: The D-glucose units in cellulose are connected by a specific type of bond known as a glycosidic linkage. In the case of cellulose, these linkages are beta-glycosidic linkages.

4. **Structure of Cellulose**: The beta-glycosidic linkages in cellulose are specifically beta 1,4-glycosidic linkages. This means that the first carbon of one glucose unit is linked to the fourth carbon of the next glucose unit in a beta configuration.

5. **Conclusion**: Therefore, cellulose is a straight-chain polysaccharide composed of only D-glucose units linked by beta 1,4-glycosidic linkages.

**Final Answer**: Cellulose is a straight-chain polysaccharide composed of only D-glucose units linked by beta 1,4-glycosidic linkages.

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