Cellulose occurs in

Options

A. Tunicates
B. Cell membrane
C. Cell wall
D. Both A and C

Answer

### Step-by-Step Solution:

1. **Understanding Cellulose**:
- Cellulose is a polysaccharide, which means it is a carbohydrate made up of long chains of glucose units linked together.

2. **Structure of Cellulose**:
- The glucose units in cellulose are linked by beta-1,4-glycosidic bonds. This specific linkage gives cellulose its structural properties.

3. **Location of Cellulose**:
- The primary occurrence of cellulose is in the cell wall of plants. The cell wall provides structural support and protection to the plant cells.

4. **Characteristics of Cellulose**:
- Cellulose does not have free aldehyde groups, which classifies it as a non-reducing sugar. This means it does not participate in redox reactions like reducing sugars do.

5. **Presence in Other Organisms**:
- Besides plants, cellulose is also found in tunicates (urochordates). Tunicates have a protective outer covering known as a tunic, which contains cellulose along with proteins and other carbohydrates.

6. **Conclusion**:
- Therefore, cellulose occurs in both the cell walls of plants and in the tunicates. The correct answer to the question is that cellulose is found in both A (cell wall of plants) and C (tunicates).