 So we talked about proteins, but proteins somehow need to be translated in that ribosome from the string of amino acids, right? And we haven't gone into that much detail about it yet. I'm going to come back to that. I think it's in lecture five or so, but I'm going to give you a sneak peek of it here. So already in 1906, Emil Fischer proposed that proteins are actually polymers that consist of amino acids. And in 1952, Fred Sanger was able to directly sequence the protein insulin and show that insulin has a unique sequence. It's always the same sequence of amino acids and insulin. And you could probably, 53 was the structure of DNA. So this was really a golden 10 or 20 years of molecular and structural biology where we found out both the sequence and structures for these proteins and how this information was encoded genetically. Fred Sanger got two Nobel prizes actually for sequencing both in terms of proteins and the DNA sequencing. And that's today what we're using all over the world, including here at SILAP lab to determine tens if not hundreds of human genomes per day. So it's amazing the speed that has happened. We're going to spend a lot of time talking about these specific sequences. So proteins are polymers in the sense that a plastic bag is a polymer. But where a plastic bag is a polymer of the same monomers, proteins are polymers of different polymers or so-called hetero polymer. The way they become polymers is literally happening inside this ribosome. And what happens in the ribosome is that we have one amino acid here and a second amino acid here. Each of these amino acids is fairly simple. We have a C-alpha atom, which is the atom in the middle. Before that, in amino acid, we have a nitrogen. Before the nitrogen, the nitrogen is actually bound to some hydrogen tube, but I'm not going to show those to make life easier. After the alpha carbon, we have a second carbon, which is actually not the beta carbon. This gel is called carbon. The beta carbon would be the side chain. And that carbon is bound to an oxygen. And then we have something called a side group that we typically denote with R. So it's a varying group that is different in different amino acids. And it's quite common to draw these large molecules this way and just ignore all the hydrogens because it makes our life simpler. Now, normally, these are quite charged. So we have kind of a plus one charge here in solution and a minus one charge here. If we take two amino acids like this, they can actually merge under some conditions. So we remove the OH here from the first amino acid and we remove the H from the second amino acid. And then they're going to form a bond. And this bond, if I draw the next amino acid here, we would then have a nitrogen and then I'm actually going to draw the hydrogen here. And then we have the next C-alpha here. This is a very special bond. This entire group is occasionally what we refer to as a peptide group or the peptide bond. And you're going to have the electrons will resonate in an entire plane here. So there are two planar centers here. So this entire bond is going to be stiff. Once it has formed, we can no longer rotate around that bond. And this will mean that there is some degree of freedom in this chain. We can rotate around that bond and we can rotate around that bond. But we can no longer rotate around this bond. We're going to spend lots of time. Already in the next lecture, we're going to talk a little bit about the degrees of freedom here. What that will mean for various proteins. And then we're going to spend some time later on in the class introducing you to different amino acids and what their properties are and how this starts to influence protein folding.