Microbiology Practice Exam 2025 – 400 Free Practice Questions to Pass the Exam

Ribosomes are essential cellular structures found in all prokaryotic organisms, making them the correct answer. Prokaryotes, which include bacteria and archaea, lack membrane-bound organelles, such as nuclei, mitochondria, and chloroplasts. Instead, ribosomes in prokaryotes are involved in protein synthesis and are critical for cellular function. They are smaller than those found in eukaryotes but perform the same fundamental role in translating genetic information into proteins.

The other options consist of organelles that are characteristic of eukaryotic cells. For instance, a nucleus, which houses the cell's genetic material, is absent in prokaryotes as their genetic material is typically organized in a single circular DNA molecule located in the nucleoid region. Mitochondria and chloroplasts are also membrane-bound organelles found in eukaryotic cells, where mitochondria are involved in energy production through respiration, and chloroplasts are crucial for photosynthesis in plants. Since prokaryotes do not possess these organelles, they are not found in any prokaryotic organism.