Which of the following is correctly classified as a secondary metabolite produced by microorganisms?

• A. Amino acids
• B. Ethanol
• C. Penicillin
• D. Lactic acid

Answer: (C)

Verified step by step guidance

1. Understand the difference between primary and secondary metabolites: Primary metabolites are compounds directly involved in normal growth, development, and reproduction (e.g., amino acids, ethanol, lactic acid), while secondary metabolites are not directly involved in those processes but often have ecological functions such as defense (e.g., antibiotics like penicillin).
2. Identify the examples given: Amino acids, ethanol, and lactic acid are all primary metabolites because they are essential for microbial growth and metabolism.
3. Recognize that penicillin is an antibiotic produced by certain fungi and is classified as a secondary metabolite because it is not essential for the producing organism's growth but provides a competitive advantage by inhibiting other microbes.
4. Confirm that among the options, penicillin fits the definition of a secondary metabolite due to its role and biosynthetic origin.
5. Conclude that penicillin is correctly classified as a secondary metabolite produced by microorganisms.