What atoms are present in a planar unit in a protein chain?

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Hi, welcome back. Our next problem says, identify the planer units present in the following generic protein chain. And we have a protein drawn in the format of we have our amino acid backbones and then the R groups are just indicated as R one R two, et cetera. So we need to think about the geometry of these bonds. Well, we know that single bonds around a carbon have tetrahedral geometry and then carbon triple bonds such as our CEO and excuse me, double bond, which is our co double bond will exhibit a trigonal planer geometry. So our tetrahedral geometry will not all be this in the same plane, but trigonal planar as its name indicates, all of the bonds to that carbon with a double bond are in the same plane. So in the case of our protein, we can trace that carbonel group. So the C double one to the O is in the same plane as the alpha carbon next to it, which is in the same plane as the nitrogen next to it. Then the, each of those the carbon, the carbon, the alpha carbon has two single bonds. So you wouldn't expect that to be in the same plane. However, so that would leave you to indicate that you have these, these planes or the same plane just surrounding the carbonel group. However, let's recall when we look at the structure, not just of a single acid amino acid, but a polypeptide. So I've drawn the alpha carbon here. So nitrogen, alpha carbon, you can have the localization the electrons because you have a carbonel group next to an amine, you essentially have an amid group here. That means you're gonna have de localization of those electrons. And we indicate that by saying there is an alternate resonance structure where my carbon carbon has a single bond to a negatively charged oxygen and a double bond to its neighboring nitrogen, which now that has an NH and then a bond two, the alpha carbon of the next amino acid has a positive charge. So essentially, it has a partial double bond character along with this carbonel group. And if the double bond exists between the carbon and the nitrogen, then the that is the trigonal planar geometry. And that would encompass the n the H the neighboring alpha carbon and the carbon carbon. So due to that possibility of electron de localization, when we look at the whole trigonal planar unit, going to erase the highlighting I did since that only included, included the one double blonde, my entire trigonal planner unit would enc encompass the carbon or the alpha carbon, excuse me, the carbon group co the nitrogen and its hydrogen, let me redraw that a little bit. So the off carbon up to the carbonel group, including the cneo way over two, the next alpha Carmen and then including the nitrogen and the hydrogen. This big box including alpha carbon, carbonyl nitrogen and hydrogen. And next alpha carbon. So there's one planar unit and then we'll see that repeated again. So the alpha carbon including the carbon carbon also including the neighboring alpha carbon and the NH group. So the second planar unit and then with our third carbonell group, alpha carbon carbonel group, next alpha carbon and an age group. So you can see here that we have three planar units and the way they arrange again reflects that you have this de localization over what's essentially an amid on the peptide bond between the two amino acids. So we'll see you in the next video.

What atoms are present in a planar unit in a protein chain?

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Key Concepts

Amino Acids

Peptide Bonds

Planar Structure