Question

Media that contain some chemical with unknown chemical composition is called __________ media.

• A. Synthetic
• B. Enrichment
• C. Complex
• D. Selective

Hint:

Remember the core difference: {Synthetic = Defined/Known}. {Complex = Undefined/Unknown} (contains natural extracts). Enrichment and Selective media are classified by their function, not just their composition.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
This question asks to classify a microbiological culture medium based on the knowledge of its chemical components. The key detail is that some ingredients have an "unknown chemical composition."
Step 2: Detailed Explanation:
Culture media can be classified based on their composition:
Synthetic or Defined Media: In these media, the exact chemical composition is known. Every component is a pure chemical with a known formula and concentration.
Complex or Undefined Media: These media contain at least one ingredient whose chemical composition is not precisely known. Such ingredients are often derived from natural sources, like yeast extract, beef extract, peptone, or tryptone. These extracts provide a rich mix of nutrients, but the exact amounts of each chemical are variable and unknown. The question's description fits this category.
Enrichment Media: These are usually liquid media containing specific nutrients that favor the growth of a particular desired microbe, which may be present in low numbers in a mixed sample.
Selective Media: These media contain components that inhibit the growth of unwanted microbes while allowing the desired microbes to grow.
Step 3: Final Answer:
A medium containing chemicals of unknown composition, such as yeast extract or peptone, is called a complex medium.