Ribosomes consist of two subunits, each made up of rRNA and proteins. The small subunit is responsible for reading the mRNA, while the large subunit joins amino acids to form a polypeptide chain. In eukaryotic cells, ribosomes are approximately 80S in size, composed of a 60S large subunit and a 40S small subunit. In prokaryotic cells, ribosomes are smaller, about 70S, with a 50S large subunit and a 30S small subunit.
