Indicate whether each of the following statements describes primary, secondary, tertiary, or quaternary protein structure:
c. Several polypeptides in a beta-pleated sheet are held together by hydrogen bonds between adjacent chains.

Question

Indicate whether each of the following statements describes primary, secondary, tertiary, or quaternary protein structure:

c. Several polypeptides in a beta-pleated sheet are held together by hydrogen bonds between adjacent chains.

Accepted Answer

All right. Hello everyone. So this question is asking us to determine if the statement below refers to the primary secondary tertiary or ordinary pro protein structure. And the statement says a polypeptide chain coils into a spiral like staircase that is stabilized by hydrogen bonds. So here we have four different answer choices labeled A through D proposing which level of protein structure the statement is describing from primary to ordinary. So first let's very briefly clarify what each level of protein structure means. And then we can talk about the statement here specifically. So starting off with the primary structure, the primary structure, if you recall is just the sequence of amino acids that make up a polypeptide chain. So we're just talking about the amino acids that are present in the order in which they're in that polypeptide chain from there, those amino acids specifically the backbone, the peptide bond backbone can interact and involve local folding in the secondary structure. So here the secondary structure just to clarify is characterized by local folding because of interactions between atoms of the peptide bond backbone and these interactions are characterized by hydrogen bonding. Right? Examples include the alpha helix and the beta sheet or beta pleated sheet. And at this point, we move on now to the tertiary structure which at this point is going to involve the side chains of the amino acids in the polypeptide. Because the tertiary structure of a protein refers to the three dimensional shape of that particular polypeptide chain. And the tertiary structure unlike secondary structure is limited or is not limited rather to just hydrogen bonding. Examples of other interactions that take place to stabilize a tertiary structure include ion bridges, even covalent bonds in the case of the disulfide bridge and also hydrophobic interactions. So many different things can stabilize a tertiary structure. Now, the tertiary structure talks about only one polypeptide and at this point, we can move on now to the level of the co ordinary structure. And the co ordinary structure involves the arrangement of multiple polypeptide chains. And so proteins like hemoglobin that have multiple different sub units have a co ordinary structure because of how those subunits interact with each other. So now that we've talked a little bit about definitions, let's go ahead and focus on the statement given we're talking about one polypeptide peptide chain coiling into a spiral like staircase by hydrogen bonds specifically. Now, at this point, what sticks out to me is that hydrogen bonding is specifically mentioned and recall that the spiral like staircase that's being described is characteristic of an alpha helix. So an alpha helix stabilized by hydrogen bonds is an example of secondary structure, meaning B is the correct answer and there you have it. So with that being said, thank you so very much for watching and I hope you found this helpful.

Indicate whether each of the following statements describes primary, secondary, tertiary, or quaternary protein structure:
c. Several polypeptides in a beta-pleated sheet are held together by hydrogen bonds between adjacent chains.

Verified video answer for a similar problem:

Key Concepts

Protein Structure Levels

Beta-Pleated Sheet

Hydrogen Bonds in Proteins