Any arrangement of these three letters (e.g. AGT) forms a code word The ribosomes identify each three-letter word as one of a total of 20 protein components. For instance, the instruction of the code “AGT” reads as follows: “Take the component called serine and attach it to the chain of components already assembled.” Further codes follow until component after component has been joined together to form a protein. Finally, a code word has its turn which gives the following signal to the protein factory: “Now the protein has been completed.”