 I'm Spencer Whitney, I'm a professor here at the Australian National University and I'm part of the Centre for Translational Photosynthesis. So what my academic career has been about is actually engineering enzymes. We want to understand their function, how they work and how they actually improve them. So how do we tweak them? But before we do that obviously we need to understand how enzymes are put together and how they have their substrate specificity. So look, listen and learn. Proteins in nature are made up of 20 different types of amino acids. And the nature of the protein is dependent on the order in which you have those amino acids. So every amino acid has a similar core structure. It all starts with the alpha carbon which has a hydrogen bound. On one side it has an amino group and on the other it has a carboxyl group. Now how amino acids differ is in the side chain. So the size, the shape and the charge of this side change is what distinguishes all the amino acids from each other. Now to actually take an amino acid and join it to another to start forming what we call a peptide or a polypeptide is this occurs by the formation of a peptide bond where we see the amino group of one amino acid joins to the carboxyl group of the other and during this process we get water is released. So that means this is called a condensation reaction or otherwise known as a dehydration synthesis due to the loss of water. So as we grow the peptide chain by continually adding different amino acids we form these polypeptides. And these polypeptides are what forms the backbone of proteins. And as we show here we can simply show this as linkages. Okay so here we have our arrangement of all our amino acids which we want to join together to form a protein. So we do that as we just talked about by forming peptide bonds. So we make these structures which are the polypeptides. Now these polypeptides what they can do is they can fold and form bonds between these side chains from the different amino acids such that we go from having a primary structure into having a secondary structure. So no longer is it a linear molecule and in reality what proteins are is actually a quaternary structure such that they actually form a three dimensional shape. So if we can imagine that this is a folded protein. Now of course in nature the enzymes which are just proteins which form biological functions actually can comprise multiple subunits. So for the enzyme to be functional we need to assemble these subunits. So as we can imagine here here's an enzyme which isn't quite right. And so it's actually quite unstable it can't actually do its function and falls apart. But once an enzyme forms so here we've got an enzyme which is made up of multiple subunits. We've got nine subunits on the top the bottom and eight round the middle. And so now we actually have a functional enzyme which can do its job. I think the real is is that proteins depending on how many enzymes depending on how many proteins they form together dictates their size and some enzymes actually comprise multiple components. And this is where they form a quaternary structure.