Now when it comes to the alpha helix, we can say that it adopts an optimal shape. Here, we're going to say that the spiral-like staircase adopts a right-handed or clockwise shape. This is basically just how the staircase twists and turns. Which direction does it take? We'd say that this is a right-handed or clockwise direction, i.e., shape. Now here we're going to say that the hydrogen bonds lie within the helix. So remember, we have hydrogen bondings that are helping to stabilize this structure. So we show these dotted lines that are helping to create the staircase, and the amino acid R groups lie outside the helix because of spacing. So if we take a look at these two images, we'd say here that this represents our right-handed alpha helix. We have our hydrogen bonding that's happening in between. And then here, we have our R groups. Because of spacing, they can't be inside of the staircase or the helix; they'd be represented outside of it. So we'd have an R group here, here, and in all of these places.
Now, in addition to this, we can say that the hydrogen bonding of the amide hydrogen and the carbonyl oxygen happens or residues further on the helix. Now, what is the result of this? Well, the result is that for every one turn of the helix, it contains an average of 3.6 residues. This is going to become important because they could ask you questions in terms of how many turns you would have if you have this many number of residues or if you have this many number of residues, how many theoretical turns could your alpha helix possess? Right. So there's a connection: for every one turn, there are 3.6 residues on average. Right. So keep this in mind when we talk about alpha helices, their optimal shapes, and the number of residues per turn.
