Everyone, now we're going to take a look at the second step of translation, which is elongation. Here in elongation, a second tRNA approaches and binds to the next codon in the complex. Remember, we had our large subunit and our small subunit joined together to complete the initiation step. We had our methionine-carrying tRNA come and pair up with the codons of mRNA. Now, a second tRNA with another type of amino acid comes and docks in this second slot here. We're going to say here that a peptide bond forms between methionine (M) and the second amino acid, in this case, serine, and it passes.
Now, we have another event here. The second tRNA has docked in with its anticodon to pair up with the codons of mRNA. What happens now is this methionine is going to break off from this tRNA and come over here to help make this bond, this peptide bond. Now, this tRNA no longer has its amino acid attached. It no longer has methionine. What's going to happen is that we have translocation where the whole ribosome moves to the next codon after the first tRNA leaves the complex.
Basically, what happens is this whole structure, the large and the small subunits, are going to shift over to the right. Because here, this tRNA is empty now. We don't need it, so we shift the whole thing over. Now, here's this codon that was within the complex, it's now out here exposed. And we're going to jettison this empty tRNA. So this would be step f. This is translocation. The whole complex shifts over to this slot here, which has this growing peptide sequence going on. And what's going to happen is, over time, we're going to make that peptide chain longer and longer, adding more and more to it.
Now, here we're going to say steps d and f keep repeating. So we have another tRNA come in, the amino acid's going to break off and help to make the chain longer and longer. It keeps on repeating. Now, if we take a look here, this is just happening at one location, but in reality, a single mRNA can be translated by multiple ribosomes simultaneously. So here is our mRNA here and here's a ribosomal complex, here's another one. They're making these peptide chains, these sequences at the same time. So, we can make multiple peptide sequences at the same time off of the same mRNA strand.
Just remember, when we're talking about elongation, we're basically starting to add and chain amino acids together through these peptide bonds. This is the way the ribosomal complex works, where a new tRNA with a new amino acid attached comes and docks in next to the older one, in this case, a methionine-containing tRNA. And we're just going to try to make the peptide bonds to make our peptide sequence longer and longer.