Microbiology Practice Exam

What is the total number of prokaryotic ribosome subunits?

1. 60

2. 80

3. 70

4. 50

The correct answer is: 70

In prokaryotic cells, the ribosome is composed of two subunits: the small subunit and the large subunit. These subunits combine to form a complete ribosome that is crucial for protein synthesis. The small subunit in prokaryotes is identified as having a sedimentation rate of 30S, while the large subunit has a sedimentation rate of 50S. When these two subunits come together, they produce a functional ribosome that has a total sedimentation rate of 70S. This existence of the 70S ribosome is characteristic of prokaryotic organisms such as bacteria and archaea, distinguishing them from eukaryotic ribosomes, which generally have a sedimentation rate of 80S due to larger subunits. Understanding the structure and function of ribosomes is fundamental to microbiology, as it provides insights into the differences between prokaryotic and eukaryotic cells, as well as the mechanics of protein synthesis.