The most abundant organic molecule is

Options

A. RuBisCO
B. Starch
C. Cellulose
D. Chitin.

Answer

To solve the question "The most abundant organic molecule is," we will analyze the provided options: Rubisco, starch, cellulose, and chitin.

### Step-by-Step Solution:

1. **Understanding the Options:**
- **Rubisco:** This is an enzyme involved in the process of photosynthesis, specifically in the fixation of carbon dioxide. It is not a molecule that is abundant in terms of organic compounds.
- **Starch:** This is a polysaccharide that serves as a storage form of energy in plants. While it is abundant in plants, it is not the most abundant organic molecule globally.
- **Cellulose:** This is also a polysaccharide, but it is the primary component of the cell wall in plants. It is formed from long chains of glucose units linked by beta-1,4-glycosidic bonds. Cellulose is known to be the most abundant organic molecule on Earth.
- **Chitin:** This is a polysaccharide that forms the exoskeleton of arthropods and the cell walls of fungi. While it is significant, it is not as abundant as cellulose.

2. **Analyzing Cellulose:**
- Cellulose is a structural polysaccharide that provides rigidity and strength to plant cell walls. It is produced in large quantities by plants during photosynthesis and is a major component of plant biomass.

3. **Conclusion:**
- After evaluating all the options, it is clear that cellulose is the most abundant organic molecule on Earth, primarily due to its widespread presence in plants.

### Final Answer:
The most abundant organic molecule is **cellulose**.

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