Which of the following is not a biopolymer?

Options

A. Proteins
B. Rubber
C. Cellulose
D. RNA

Explanation

To determine which of the following options is not a biopolymer, we need to understand the definition of biopolymers and analyze each option provided.

### Step-by-Step Solution:

1. **Understanding Biopolymers**:
- Biopolymers are polymers that are produced by living organisms. They are made up of monomeric units that are derived from biological sources.

2. **Analyzing the Options**:
- **Option A: Proteins**:
- Proteins are polymers made from amino acids, which are produced in the cells of living organisms. Therefore, proteins are biopolymers.

- **Option B: Rubber**:
- Rubber is obtained from the latex of trees. However, the latex is derived from the bark of trees, which is a non-living part of the tree once it has been harvested. Thus, rubber is not produced by living cells and is not considered a biopolymer.

- **Option C: Cellulose**:
- Cellulose is a polysaccharide made from beta-D-glucose units. It is produced by plants and forms the cell wall, making it a biopolymer.

- **Option D: RNA (Ribonucleic Acid)**:
- RNA is a nucleic acid that plays a crucial role in the synthesis of proteins in living organisms. It is produced in cells and is therefore a biopolymer.

3. **Conclusion**:
- Based on the analysis, the only option that is not a biopolymer is **Option B: Rubber**.

### Final Answer:
**Rubber is not a biopolymer.**

---