Which small subunit size is found in eukaryotic ribosomes?

In eukaryotic ribosomes, the small subunit is identified as 40S. This designation reflects the sedimentation coefficient, which is a measure of the size and density of the ribosomal subunit. The 40S subunit contains the ribosomal RNA and proteins that play crucial roles in the initiation of translation and the overall process of protein synthesis.

Ribosomes consist of two subunits: the small subunit, which in eukaryotes is 40S, and the large subunit, which is 60S. Together, they form the complete ribosome, functioning as a complex machine that translates messenger RNA (mRNA) into polypeptide chains, ultimately leading to protein synthesis. Understanding the different sizes of ribosomal subunits is important in molecular biology, as it reflects differences in ribosomal structure and function between eukaryotes and prokaryotes, where the small subunit is 30S.