This figure shows the ribosome structure in prokaryotes (a) and eukaryotes (b). Part (a) shows the prokaryote 70S ribosome which is comprised of a large, 50S, and small, 30S, subunit represented as two blue ovals labelled 50S (top) and 30S (bottom). Part (b) shows the eukaryote 80S ribosome which is comprised of a large, 60S, and small, 40S, subunit represented as two blue ovals labelled 60S (top) and 40S (bottom). The large subunit of both ribosomes is responsible for creating the links in the growing amino acid chain. The small subunit in both ribosomes is where mRNA carrying the instructions for making protein binds. The Svedberg unit (S) indicates the size, shape and density of each subunit.