Which of the following is a primary metabolite ?

Options

A. Carotenoid
B. Glucose
C. Morphine
D. Cellulose

Answer

To determine which of the following is a primary metabolite, we need to understand the definitions and characteristics of primary and secondary metabolites.

### Step-by-Step Solution:

1. **Understand the Types of Metabolites**:
- **Primary Metabolites**: These are compounds that are directly involved in the metabolic processes necessary for the growth, development, and reproduction of an organism. Examples include carbohydrates, proteins, lipids, and nucleic acids.
- **Secondary Metabolites**: These are not directly involved in the basic metabolic processes. They are often produced as intermediates or have ecological functions, such as defense mechanisms or pigmentation. Examples include alkaloids, terpenoids, and flavonoids.

2. **Analyze the Options**:
- **Carotenoids**: These are pigments found in plants and are considered secondary metabolites. They are not essential for the basic metabolic functions of growth and reproduction.
- **Glucose**: This is a simple sugar that serves as a primary energy source for cellular respiration, making it a primary metabolite essential for growth and metabolism.
- **Morphine**: This is an alkaloid derived from the opium poppy and is classified as a secondary metabolite, as it is not directly involved in the growth or metabolic processes of the organism.
- **Cellulose**: This is a structural component of plant cell walls and acts as dietary fiber in humans. While it is important for structure, it is not a primary metabolite because it does not directly participate in metabolic pathways.

3. **Identify the Correct Answer**:
- Among the options provided, **glucose** is the only compound that qualifies as a primary metabolite because it is directly involved in metabolic pathways and is essential for energy production and growth.

### Conclusion:
The correct answer is **glucose**.

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