Question

Which of the following is a primary metabolite?

• A. Antibiotics
• B. Ethanol
• C. Penicillin
• D. Taxol

Hint:

• Primary metabolites Essential for growth, development, reproduction. Produced during active growth. Examples: amino acids, alcohols, organic acids, vitamins, nucleotides.
• Secondary metabolites Not essential for growth. Often have ecological roles or specialized functions. Examples: antibiotics, pigments, toxins, alkaloids.

Answer 1

The Correct Option is B

Metabolites are intermediates and products of metabolism. They are broadly classified into primary and secondary metabolites.

• Primary Metabolites: These are compounds that are directly involved in the normal growth, development, and reproduction of an organism. They are essential for the life of the cell and are typically produced during the exponential growth phase (trophophase). Examples include amino acids, nucleotides, vitamins, organic acids (like citric acid, lactic acid), alcohols (like ethanol from fermentation), and components of central metabolic pathways (like glucose, pyruvate).
• Secondary Metabolites: These are organic compounds that are not directly involved in the normal growth, development, or reproduction of the organism. They often have ecological functions (e.g., defense, signaling) or are produced during the stationary phase (idiophase) or under stress conditions. Examples include antibiotics, toxins, pigments, alkaloids, and some pharmaceuticals.

Let's analyze the options: (a) Antibiotics: These are classic examples of secondary metabolites, produced by microorganisms often to inhibit the growth of other competing microbes. (b) Ethanol: Ethanol is a product of alcoholic fermentation, which is a primary metabolic pathway for energy generation (from glycolysis) in some yeasts and bacteria under anaerobic conditions. It's directly linked to the central energy metabolism. (c) Penicillin: An antibiotic produced by Penicillium fungi. It is a secondary metabolite. (d) Taxol (Paclitaxel): A complex diterpene produced by yew trees, used as an anticancer drug. It is a secondary metabolite. Therefore, ethanol is a primary metabolite among the given options, as it is a direct product of a primary energy-yielding pathway (fermentation linked to glycolysis). \[ \boxed{\text{Ethanol}} \]