How do ribosomes make proteins?

The ribosome reads the mRNA one codon at a time, adding protein building blocks one by one. The building blocks are made up of amino acids attached to transfer RNA (tRNA) molecules. For every codon in the mRNA, there is a tRNA molecule that fits it exactly. As the ribosome moves along the mRNA, it selects the correct tRNA molecules. Each tRNA brings with it the correct amino acid, which the ribosome then adds to the growing protein, releasing the tRNA at the same time.