When a protein folds into its tertiary structure, does the pri...

Question

When a protein folds into its tertiary structure, does the primary structure change? Explain.

Accepted Answer

Alright. Hello everyone. So this question is asking us in the context of protein structure. What is the impact of tertiary structure formation on the primary structure of the individual polypeptide chains involved? So here we have four different entry choices labeled A through D proposing whether or not the primary structure gets rearranged remains the same forms a new sequence or replaces a different polypeptide chain. These are the options that we have. So I think it's best to just go ahead and start with the levels of protein structure and then go from there. So the primary structure, which is the focus of this question, right is simply put the sequence of amino acids. So the primary structure just to rephrase is the sequence of amino acids linked by peptide bonds to create a polypeptide. And so from this point, when talking about the secondary tertiary or ordinary structures, it's important to recognize that these interactions that form the complete protein are the result of interactions between those amino acids in the primary structure. And so moving on from here to the next level, we move on to secondary structure. Now, secondary structure can be summarized by the phrase local folding because it talks primarily about the interactions between the atoms of that backbone. Because recall that when talking about the primary structure, these amino acids were linked together via peptide bonds, right to create a backbone. And so the secondary structure can be described as local folding between the atoms that make up this peptide bond backbone. This is how we get structures like alpha helices and beta sheets. So at this point, the polypeptide has now begun to fold and then we can introduce the tertiary structure. Now, the tertiary structure is characterized by interactions between amino acid side changes. Because after secondary structure, right after the level of folding in the secondary structure, amino acids on further ends of the chain are beginning to to be brought closer together. So now by the time we get to cir to tertiary structure, amino acid side chains can participate in various different interactions depending on whether or not they're polar nonpolar ionic, et cetera. And so at this point, we've talked about the elements of structure formation of proteins that have one polypeptide chain. And so ordinary structure is relevant to proteins like hemoglobin that are composed of multiple different subunits, multiple different polypeptide chains that undergo their own folding process. And so the co ordinary structure for these more complex proteins is simply the interactions between subunits interaction between different polypeptide chains to produce the more complex protein. So now we can analyze the relationship and the question, what does it mean to change the tertiary structure from the perspective of the primary structure? Now, here it's important to recognize that tertiary structure describes non covalent interactions between amino acid side chains except for disulfide bridges. Because those are in fact COVID. So folding in the context of tertiary structure is talking about really the spatial arrangement of amino acids. But are we changing the sequence of amino acids? No, right, Because by the time tertiary structure is forming, right, by the time that level of folding is taking place, the primary sequence has already been done, the primary structure is already complete. Now, on the other hand, changing the primary structure, changing the sequence of amino acids can and will change the tertiary structure but not the other way around. So all this is to say that the correct answer here is going to be option B because the primary structure of each polypeptide chain remains unchanged and there you have it. So with that being said, thank you so very much for watching and I hope you found this help.

When a protein folds into its tertiary structure, does the primary structure change? Explain.

Key Concepts

Primary Structure of Proteins

Tertiary Structure of Proteins

Protein Folding

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