What is an agar plate used for?

• A. To store liquid samples in a chilled environment.
• B. To measure the viscosity of gels.
• C. To perform electrophoresis separation.
• D. A petri dish filled with a jello-like nutrient material used to grow bacteria upon.

Answer: (D)

Agar plates are used to grow bacteria on a solid, nutrient surface. They’re petri dishes filled with agar, a jelly-like substance that provides a stable medium for microorganisms to grow when incubated. This setup lets you see and study colonies, count how many organisms are present, observe colony shape and color, and test how bacteria respond to different antibiotics or conditions. The other ideas don’t fit because storing liquid samples in a chilled environment relies on cold storage, measuring viscosity needs a viscometer, and electrophoresis uses gels to separate molecules under an electric field, not to cultivate microbial growth. So, the purpose is to culture bacteria on a nutrient-containing surface.