Which of the following is not a secondary metabolite?

Options

A. Glycerol
B. Morphine
C. Cellulose
D. Ricin

Answer

To determine which of the following options is not a secondary metabolite, we need to understand what secondary metabolites are and analyze each option provided.

### Step-by-Step Solution:

1. **Understand Secondary Metabolites**:
- Secondary metabolites are organic compounds that are not directly involved in the normal growth, development, or reproduction of an organism. They often play important roles in plant defense, pollinator attraction, and competition with other plants.

2. **Analyze the Options**:
- **Option A: Glycerol**
- Glycerol is a simple polyol compound. It is a colorless, odorless, viscous liquid that is sweet-tasting and non-toxic. Glycerol is primarily involved in metabolic processes and is not classified as a secondary metabolite.

- **Option B: Morphine**
- Morphine is an alkaloid, which is a type of secondary metabolite. It is derived from the opium poppy and is used for its analgesic properties.

- **Option C: Cellulose**
- Cellulose is a polysaccharide that is a primary structural component of plant cell walls. While it is a complex carbohydrate, it is not classified as a secondary metabolite.

- **Option D: Resin**
- Resin is a sticky substance produced by many plants, particularly conifers. It is considered a secondary metabolite as it plays a role in plant defense.

3. **Conclusion**:
- Among the options, Glycerol is not a secondary metabolite. Morphine, Cellulose, and Resin are associated with secondary metabolite functions, but Cellulose is primarily a structural component and not a secondary metabolite in the traditional sense. However, since Glycerol is clearly defined as not being a secondary metabolite, the correct answer is **Glycerol**.

### Final Answer:
**Glycerol** is not a secondary metabolite.