Primary Structure of Protein - Video Tutorials & Practice Problems
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concept
Primary Protein Structure
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in this video, we're gonna talk about the primary structure of a protein. So in our last lesson video, we said that free amino acids that are separate and independent from one another can actually be co violently linked together in a chain via peptide bonds to create ah poly peptide chain. And so once these free, independent amino acids are actually linked together, they're referred to as amino acid residues. And so all the residue is is an amino acid that has been linked in a poly peptide chain. And so when biochemist referred to the primary protein structure, they're really referring to both the amino acid composition and the sequence of amino acid residues in a chain. And so the composition is really referring to both the number or the quantity and the types of amino acids that are present. But it doesn't include the order that the amino acids coming, and that's where the sequence comes into play because the sequence is the particular or the exact order of amino acid residues, specifically from the n terminal end of a protein to the C terminal end of a protein. And so, in our example below, we're gonna talk about the primary protein structure and how it consists of composition and sequence. And so what we have is on the far left. Here is the composition and on the right, what we have is the sequence. So we're gonna talk about the composition first and recall that the composition is the number and the types of amino acids. So the composition will tell us that there is a total of six amino acids and it will tell us that there's Onley, one each of veiling Allan e, meth, inning and fennel, Allan E. And that there are two glistens. But again, it's not going to tell us the order that these amino acids coming So we have no idea veiling comes first or glisten come first. We have no idea. And so also noticed that these amino acids here are not linked via peptide bond. So they're free and independent from another one another. So they are free amino acids. And so, as you guys already know, free amino acids all have an end terminal end. So they all have an amino group and a car boxing group. So that is true for all of them. Now I'm not gonna draw all of this for all of them, but we already know that free amino acids having amino group and a car boxing group, and they're free and ionized able. And so when we consider the sequence over here, notice that now these amino acids are actually linked together, and they're linked by these black lines here between the amino acids. And so these black lines are the peptide bonds, and we know that once an amino acid is linked to a chain in a pep type with a peptide bond, it's referred to as an amino acid residue. And so these air all amino acid residues and notice that our protein chain here has two different end has the end terminal end, and it has a C terminal end on the opposite end. And whenever you're considering the sequence of a protein, it's always going to be from the n terminal end to the C terminal end. Even if it's not indicated, that's just always the assumption and biochemist always consider sequence from n terminal toe, the C terminal. It's like writing a sentence in English. You always write it from left to right in the you always start with a capital letter. So the n terminal end on you always end with punctuation of C terminal. And so that's just the way that it is. And so we know that on the end terminal end over here that there's going to be a free amino group. So in the amino groups at Physiological Ph. R. NH three with a positive charge and then the C terminal end here, the C stands for the car boxful group. So we know it's gonna be a free car, Boxley and I and at physiological pH. And so notice that these internal amino acid residues actually don't have these ionized able or free, uh, groups. They don't have free amino groups or car boxful groups. And that's because when a peptide bond forms via dehydration synthesis reactions, we know that the amino group interacts with the car boxful group of another amino acid. And so they basically, when they interact, that gets rid of their their ability toe lionize. So these guys do not have ionized able, uh, amino groups and car boxes group. It's on. Lee gonna be the ones that are on the end. So the one on the far left will have a free amino group but lacks a car boxing group. And then the one on the far right is gonna have a free car boxer group, but lacks a free amino group. And so the last thing I wanna leave you guys off with is that, uh whenever you change either the composition or the sequence, you will change the primary protein structure so you can change the composition but still have relatively the same sequence. But if you change the composition, you're gonna change the primary protein structure as well. So keep that in mind a change toe. Either The composition of the sequence will affect the primary protein structure. And so this concludes our lesson on primary protein structure, and we'll be able to apply these concepts in our next practice problems. So I'll see you guys there.
2
Problem
Problem
Which statement regarding primary protein structure is false?
A
Amide linkages covalently keep amino acid residues in their particular order.
B
Protein composition entails both the quantity and types of amino acids, but not the order.
C
Amino acid sequences are always considered from N-terminal to C-terminal residues.
D
Each amino acid residue contains both a free/ionizable amino & carboxyl group.
3
concept
Protein Primary Structure
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2m
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so the primary protein structure is actually super important for protein. And that's because the primary protein structure actually defines a proteins overall shape and its function. And so the reason this is true is because, really, it's the primary level of structure that dictates all the other levels of structure, which include the secondary, tertiary and quaternary levels of structure, which remember we kind of reviewed those way back in Chapter one. And so, in our example below, what you can see is the impact that the primary protein structure has. And so over here on the far left, what we have is our primary protein structure and recall that the primary protein structure includes both the amino acid composition, which are the types and the quantity of amino acids, as well as the sequence of amino acid residues, which is the exact order of amino acids, specifically from the end terminal end of a protein to the C terminal end of a protein. And so what you can see is that the primary protein structure dictates all the other levels of structure, so it dictates the secondary level of structure which remember, includes the formation of Alfa jealousies and beta sheets. It dictates the tertiary level of structure, which is the overall three dimensional shape of the protein. And then it also dictates the quaternary level of structure, which is when you have multiple amino acid change that come together to form a single functional protein. And then it is also going to dictate the proteins function. So the shape ultimately determines the function that that proteins gonna have. And so remember that not all proteins have quaternary structure. So for some proteins, they could skip right around this and go straight to the protein function. But it depends on the protein. And again, we're gonna talk a lot more about all these other levels of structure secondary, tertiary and quaternary a little later in our course. But for now, just focus on how important the protein primary protein structure really is and the impact that it can have. So again, if you change the primary protein structure, you could change all of these other levels of structure and potentially change the proteins function. So primary protein structure, super super important. So that that concludes this lesson here, and I'll see you guys in our practice videos
4
Problem
Problem
A new drug cleaves some amide linkages in a polypeptide chain. Which level of structure is directly affected?
A
Primary protein structure.
B
Secondary protein structure.
C
Tertiary protein structure.
D
Quaternary protein structure.
5
Problem
Problem
Fill in the blanks with the primary sequence of the peptide. Use the 1-letter codes. Circle all the α-carbons.
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6
Problem
Problem
Fill in the blanks with the primary protein structure of the following peptide. Circle all the α-carbons.
The above peptide is an effective buffer at pH 10. Which amino acid residue is responsible for that?
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6m
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7
Problem
Problem
Identify the primary level of structure for the following peptide, which is an inhibitor of the Angiotensin I Converting Enzyme (ACE I) and a regulator of blood pressure and hypertension. Circle all the α-carbons.