Tertiary Protein Structure - Video Tutorials & Practice Problems
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concept
Tertiary Protein Structure Concept 1
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Now, we can say here that the tertiary structure of a protein is its overall 3d shape. And it's a result from the twisting and bending of a peptide chain and it's stabilized by interactions between our groups. Now, it involves both the close and distant our groups. So in terms of our journey to a fully functional protein, we had our primary structure which is just amino acids connected to each other by peptide bonds. Then we moved to secondary structures which can be alpha helix or beta pleated sheets. And now we're talking about a tertiary structure which we can see as a folded peptide chain. Now, if we take a look here in this, we have alpha hela sees as well as beta pleated sheets involved here. Remember these blue arrows here represent our beta pleated sheets. And then here we have our alpha helix. Now remember in a polypeptide chain, we can have areas of multiple alpha helices and beta pleated sheets. Not just one of each. Here, we're gonna say the folding of a of a peptide into a tertiary structure. It does not change its primary and secondary structures. Remember, this is kind of like a build up. So we get to a fully functional protein, we had our primary structure that primary structure. If we look closely parts of it can be alpha helices, parts of it can have beta pleated sheets. Tertiary structures is the continued folding of that poly peptide chain to give us this folded peptide look, which makes it one step closer to becoming a fully functional protein. We're not there yet, but we're on our way to that. So remember it's just a build up from primary to secondary to now tertiary, getting to tertiary does not erase all the work done on the primary and secondary structures. OK. So they build on top of each other. So keep that in mind when we take a look at questions dealing with tertiary structure of proteins.
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example
Tertiary Protein Structure Example 1
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Which of the following statements about primary secondary and tertiary protein structures is incorrect. The tertiary structure of a protein is stabilized by interactions between our groups of different amino acids. That's true. And remember it's close and distance are groups that are helping with the stabilization. Now here the folding of a peptide into the tertiary structure destroys its secondary structure. Remember this is incorrect. The tertiary structure being formed does not erase the primary and secondary structures. It's just an evolution more, it's becoming more complex in terms of the polypeptide chain. Ok. It's not undoing the primary and secondary structures due to the folding of the peptide chain, distant art groups come close and interact with each other. That is true with this folding in and, and and moving and twisting. Some art groups are going to have greater interactions than before. A folded peptide or protein can have alpha helices and beta pleated sheets at the same time. Yes. These polypeptide chains can be many amino acids, long portions of it can contain alpha hela seeds and portions of it can contain beta pleated sheets at the same time. So this is indeed possible. So this is correct. The only statement here that is incorrect is option B.
3
concept
Interactions within the Tertiary Structure Concept 2
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In this video, we'll talk about the interactions with the tertiary structure itself. Now, here we're going to say that the tertiary structure mostly consists of non covalent interactions. He will talk about four of them. They are hydro phobic interactions. So the portions that are afraid of water, the opposite of this is hydrophilic, the portions that like water. Next, we have hydrogen bonding and then a salt bridge salts are terms we use for ionic compounds. So salt bridge would be an ionic bond. Now here, if we take a look, let's not worry about the other ones. For. Now, if we just take a look at this portion of our peptide, we could say that this portion here that has this hydrocarbon and this hydrocarbon are groups, they are nonpolar in nature because they're hydrocarbons. So their interaction will be hydrophobic. Over here, we have this R group which has an oh group. So it has similar intermolecular force as well as polarity as the water molecules around it. So it would not be afraid of water would love water. So it'd be hydrophilic. Next, we have this R group which has an O age group and this R group, which has an O age group, this would be hydrogen bonding. And then finally, we're talking about ionic bond. So we're talking about charges salts. Here's a, here's a negative charge attracted at this positive charge. This would be our ionic bridge. This leaves this last interaction. So if we come back up here, we're gonna say a covalent bond can help to, to hold the folded peptide in place. So it kind of like ratchets it up and keeps it in place. We're gonna say we have what's called a die sufi bridge. It forms when sh groups from two cysteine residues react to form a SS bond. So here, if we look, this would be our disulfide bridge. So here we made a disulfide bond, these SS here that connect together. So this was a cysteine R group and this was a CY R group then combining when they lost their hydrogens. And what's left behind is this th disulfide bridge, this connection that's ratcheting up and connecting more strongly this alpha helix with this beta pleated sheet. So remember these are the different types of interactions that can exist with the tertiary structure. Four of them are non covalent in nature and one of them, the disulfide bridge is a covalent bond
4
example
Tertiary Protein Structure Example 2
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Which of the following interactions is the most likely to be found at the surface of a folded peptide. So if we're thinking about this, we have a folded peptide and it's in an aqueous medium. So water, if we're talking about the surface of that peptide, we're talking about its outside. If you're gonna be on the outside of the peptide, you have to make sure that you like water because water is gonna be all around you. So it's safe to say here that the interaction most likely to be found on the surface of a folded peptide would have to be a hydrophilic interaction. The portion that likes water. Now, the least likely one to be found on the surface would have to be our hydrophobic interactions. And we know that one of the first actions in folding is for the hydrophobic or water, fearing portions to fold and go on the interior of this peptide chain. All right. So just remember, hydrophobic portions are most likely to found on the inside. Hydrophilic are found on the surface of the peptide
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Problem
Problem
Which of the following amino acid pairs are the most likely to form hydrogen bonds?
A
Cysteine – cysteine
B
Lysine – glutamate
C
Serine – threonine
D
Leucine – valine
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Problem
Problem
What type of R group interaction is the most likely between the alanine and isoleucine residues?
A
Hydrogen bonding
B
Hydrophobic interaction
C
Disulfide bridge
D
Salt bridge
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Problem
Problem
Which of the following amino acid pairs can form a salt bridge?
A
Cysteine – methionine
B
Serine – glutamine
C
Valine – isoleucine
D
Lysine – glutamate
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