What are the small and large ribosomal subunits for eukaryotes?

In eukaryotic cells, ribosomes consist of two main components: the small ribosomal subunit and the large ribosomal subunit. The small subunit is identified as having a size of 40S, while the large subunit is 60S. This specificity reflects their sedimentation coefficients, which are determined using centrifugation techniques that separate ribosomes based on size and density.

The 40S small subunit is responsible for the initial stages of translation, including the binding of mRNA and initiation factors, setting the stage for protein synthesis. Meanwhile, the 60S large subunit contains the peptidyl transferase center, where the formation of peptide bonds occurs during translation. Together, these subunits come together during protein synthesis to form a functional ribosome that translates messenger RNA into polypeptides, an essential process for cellular function.

This understanding of ribosomal subunit sizes is crucial in molecular biology, particularly in studies involving protein synthesis, antibiotics that target ribosomes, and understanding the mechanisms behind certain genetic diseases.