In this video we're going to begin our lesson on proteins. Now proteins are one of the major classes of biomolecule polymers that are made up of amino acid, monomers. And so amino acids are the monomers that make up proteins. Now the covalent bonds that link adjacent amino acids together in a chain are specifically referred to as peptide bonds. And we'll be able to see some examples of these peptide bonds down below in our image. But, it's also important to note that the protein polymers are actually going to have directionality, meaning that in the chain of the protein polymer one end is going to be chemically different than the opposite end. And so we refer to these ends as the n terminal end and the c terminal end. And so let's take a look at our example image down below at the formation of proteins from amino acid monitors to get a better idea of these concepts. And so notice over here on the far left hand side, we're showing you all of these separate individual circles which represent amino acid monomers. And so these are amino acids that are separate from each other. But of course, if we join these amino acid monomers together in a chain like what we see here, then we're building ourselves a protein polymer. And notice that the protein polymer has directionality because on one end over here, it's chemically different than the opposite end over here. And so the end that has the amino group like what we see over here is referred to as the n terminal n because it the amino group has a nitrogen atom. And then this other group that we see over here on the opposite end is referred to as the c terminal end because it has a carboxyl group, which we see, over here. And then notice that each of these separate amino acid monomers are being covalently linked together through these bonds that we see right here. And these bonds that covalently link the adjacent amino acids together are referred to as peptide bonds. And so, this here really concludes our introduction to proteins and we're going to continue to talk more and more about proteins as we move forward in our course. And so I'll see you all in our next video.
2
concept
Amino Acids
Video duration:
4m
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Video transcript
In this video, we're going to talk some more details about amino acids. Now amino acids, recall from our last lesson video, are really just the monomers of proteins, and so linking together multiple amino acids allows us to build a protein polymer. Now each individual amino acid monomer is going to contain common components that are common to all amino acids, and then they're also going to contain some unique components such as the unique R group. And we'll be able to see the common components in the unique r group down below once we get to our image. But living organisms, they primarily use a total of 20 different amino acids. And once again, these different amino acids, they all have common components that we're gonna talk about, but each of the 20 amino acids also has a unique, so each has a unique r group. So let's take a look at our example down below to get a better understanding of these ideas. So we're taking a look at the amino acid structure. And so over here on the left, what we have is a table of the amino acid components. And so recall in our last lesson video, we were representing amino acids using these circles. And so, these circles, each of these circles has these components that we're talking about, and these components you can see over here in a more detailed chemical structure of the amino acid. So each of these amino acids is going to have common components which we have in the red box. So the red dotted box that you see here represent the common components that are found in all 20 of the different amino acids, And, down below what you'll see is a green shading which is gonna be the unique region of the amino acid that will differ between all of these 20 amino acids. So when we look at the common components, notice that it starts with the central carbon atom which is also known as the alpha carbon. And so over here when we look at the chemical structure you can see that the central carbon atom is right here in the center, right in the middle. Now coming up off the top of the central carbon atom we have a central hydrogen atom. So that would be this, hydrogen atom that we see here. And again, this is a common component found in all amino acids. And then going to the left and going to the right of the central carbon atom, we have these 2 functional groups that you should recognize. So going to the left over here in blue, what we have is an amino group which is where the n terminal end would be for this amino acid. And then, of course, going to the right over here in yellow, what we have is a carboxyl group which is going to be the c terminal end of the amino acid. And so once again, all of these components that we talked about here are the common components found in every single amino acid. And really what makes one amino acid different from another amino acid is going to be the r group, the unique r group. And so we can put the r group here. And the r group, you can pretty much think that the r stands for the r in the rest of the molecule because the r group is going to be variable. It will change from amino acid to amino acid and it represents the rest of the molecule. Some amino acids have a really really small r group with just a handful of atoms, just maybe one atom sometimes. And other, amino acids have R groups that are much, much larger in size and have many, many more atoms and and they're much, much more complicated. But the backbone, this region here is going to be common for all amino acids So that's important to keep in mind. Now for your biology class, you're likely not going to need to know all 20 of the different amino acids but you will need to know that there are 20. And you will need to know, the common components and the fact that they all have a unique R group that has different properties. And so this here concludes our introduction to amino acids and we'll be able to get some practice applying these concepts as we move forward in our course. So I'll see you guys in our next video.
3
Problem
Problem
The primary building blocks (monomers) of proteins are:
a) Glucose molecules.
b) Lipids.
c) Nucleotides.
d) Amino acids.
e) None of these.
A
Glucose molecules.
B
Lipids.
C
Nucleotides.
D
Amino acids.
E
None of these.
4
Problem
Problem
Which two functional groups are always found in amino acids?
a) Carbonyl and amino groups.
b) Carboxyl and amino groups.
c) Amino and sulfhydryl groups.
d) Hydroxyl and carboxyl groups.
A
Carbonyl and amino groups.
B
Carboxyl and amino groups.
C
Amino and sulfhydryl groups.
D
Hydroxyl and carboxyl groups.
5
concept
5 Protein-Related Terms
Video duration:
3m
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Video transcript
So as you guys are reading through your textbooks or sitting in class, listening to your professors, you might hear these 5 protein related terms just tossed around and used all the time. But not everyone distinguishes between these 5 protein related terms. And so here in this video we're going to specifically distinguish between these 5 protein related terms. And so these 5 protein related terms are referring to amino acid chains that vary in their length. And so notice down below we have this table that has the protein related terms over here on the left hand side, and then it has the length of the amino acid chain over here on the right hand side. And so the first protein related term that you all should know is of course, amino acid, which we already talked about in our last lesson video. So we already know that amino acids are a single protein unit or in other words, a monomer of a protein is an amino acid. And then of course we can take these individual monomers, these individual amino acids and link them together to create a long chain of amino acids. And that's where these other four terms come into play. So the second term that we have here is going to be oligopeptide. And so recall that the oligo prefix means a few. And so oligopeptides are going to have an amino acid chain that have just a few amino acids, somewhere between about 2 and about 20 covalently linked amino acids in the chain. So pretty short, amino acid chains are oligopeptide chains. Now the term peptide without the oligo prefix is referring to amino acid chains that have less than 50 covalently linked amino acids. And so what's important to note here is that oligopeptide and peptide, at some point there's a little bit of overlap between the two terms. Now the 4th term that we have here is poly peptide and recall that the prefix poly means many. And so these are going to be amino acid chains that have greater than 50 amino acids that are covalently linked together. And then the 4th the 5th and final term that we have here is protein itself. And so a protein is specifically referring to just one or multiple polypeptide chains that are specifically in their folded or functional forms. And so when we're talking about proteins, we're talking about polypeptides that are in their folded, or functional forms. And when we say folded, what we mean is that these chains don't just remain as straight linear chains, they actually fold up into themselves and create these complex three-dimensional structures. And so really this leads us to our next lesson video which is talking about the levels of structure of protein. So, I'll see you all there in that video.
6
Problem
Problem
What term is used for an amino acid chain that has greater than 50 covalently linked amino acids?
a) Protein.
b) Peptide.
c) Amino acid.
d) Polypeptide.
A
Protein.
B
Peptide.
C
Amino acid.
D
Polypeptide.
7
concept
Protein Structure
Video duration:
4m
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Video transcript
In this video we're going to discuss protein structure. And so proteins actually have a hierarchy of structure that's organized into 4 levels that are conveniently labeled primary, secondary, tertiary, and quaternary levels of protein structure. Now notice that each of the four levels of protein structure that we have in our text up above corresponds with the levels of protein structure that we have down below in our image. Now the very first level of protein structure is going to be the primary level of protein structure which can be symbolized with this symbol 1 with the not symbol here. And so the primary level of protein structure specifically refers to the types of amino acids, the quantity of amino acids, and the specific order or the specific sequence of amino acids in the protein chain. And so if we change either the types of amino acids, the quantity of amino acids, or the specific order or the sequence of amino acids in the protein chain, then we will change the primary level of protein structure. Now the primary level of protein structure is arguably the most important level of protein structure and that is because the primary level of protein structure will determine and dictate all of the other levels of protein structure. And so if we change the primary level of protein structure, then we could also potentially change either the secondary, tertiary and or quaternary levels of protein structure as well. And so if we take a look at our image down below on the left hand side, notice we're showing you an image of the primary level of protein structure. And so notice that in this image, each of these circles that you see here represent the amino acids in the protein chain and notice that these amino acids are all covalently linked together via peptide bond. Now, again, the primary level of protein structure as indicated in this image refers specifically to the types of amino acids in the chain, the quantity of amino acids in the chain and or the order or the sequence of amino acids in the chain. And so by changing either the types, quantity or order of amino acids, then we will also change the primary level of protein structure. And again the primary level of protein structure is extremely important because the primary level of protein structure will dictate all other levels of protein structure including the secondary tertiary and quaternary levels of structure. And so the next level of protein structure is going to be the secondary level of protein structure and so we can put a 2 here in this blank and the secondary level of protein structure is the formation of either alpha helices or beta sheets in the protein backbone. And so if we take a look at our image down below, what you'll notice is that this protein chain, can, then fold its backbone into either an alpha helix with as you can see here in this image where the alpha helix is somewhat of a winding staircase type of structure, or the protein backbone could form a beta sheet which is a more elongated extended zigzag type of structure. Up down up down. And so, the secondary protein structure again refers specifically to the formation of either alpha helices, this winding staircase structure, or beta sheets, this zigzag structure, in the protein backbone. Now the next level of protein structure is the tertiary level of protein structure, and so we can go ahead and put a 3 here in this blank and the tertiary level of protein structure is easy to remember because the 3 that's associated with the tertiary can remind you of the 3 in three d. And so the tertiary level of protein refers to the overall three d or three-dimensional shape of the polypeptide chain. And so if we take a look at our image down below what you'll notice is that once the protein backbone folds into alpha helices and beta sheets then the entire protein chain can then take on an overall three-dimensional shape as you see here. And so, this is the tertiary protein structure, when we consider the overall three-dimensional shape of the entire chain. And so within this overall three-dimensional shape, you can see that alpha helices can be embedded in there as well as beta pleated sheets. So these levels of protein structure are building on each other. Now, what's important to note is that all proteins are going to have primary, secondary and tertiary levels of protein structure, but not all proteins will have a quaternary level of protein structure. Only some proteins will have a quaternary level of protein structure. Now the quaternary level of protein structure again can be symbolized with a 4 here, with this symbol and the quaternary level of protein structure, is when a protein has multiple polypeptide chains that are going to associate with each other to form a single functional protein. And so, if we take a look at our image down below what you'll notice is that this one protein chain here with tertiary structure is 1 polypeptide chain. But if this 1 polypeptide chain associates with other polypeptide chains then it would have a quaternary structure. So for example, this one polypeptide chain, could be this one polypeptide chain as you see right here, and it could associate with another polypeptide chain, that's up here in the top right and it could associate with another one over here and a 4th one over here. And so what you'll notice is when you have these separate polypeptide chain each with their own tertiary structure that come together to form a single complex. So all 4 of these separate chains coming together to form a single complex where this would be a complex of 4 separate polypeptide chains, that would be a protein that has quaternary structure. And so once again, a protein that has quaternary protein structure is going to have multiple amino acid chains that complex together or multiple polypeptide chains that complex together And so this specific quaternary, this specific protein that has quaternary level of structure is supposed to represent a protein called hemoglobin which is a protein that is found in our red blood cells and helps to transport oxygen to our tissues. But really, this here concludes our brief lesson on protein structure and how it consists of primary, secondary, tertiary, and quaternary levels of structure and, we'll be able to get some practice applying these concepts as we move forward. So I'll see you all in our next video.
8
Problem
Problem
The specific amino acid sequence in a protein is its:
a) Primary structure.
b) Secondary structure.
c) Tertiary structure.
d) Quaternary structure.
A
Primary structure.
B
Secondary structure.
C
Tertiary structure.
D
Quaternary structure.
9
Problem
Problem
Which of the following is true of protein structure?
a) Peptide bonds are formed by hydrolysis.
b) Peptide bonds join the amine group on one amino acid with the R group of another amino acid.
c) Secondary protein structures are caused by hydrogen bonding between atoms of the peptide backbone.
d) Tertiary protein structure emerges when there is more than one polypeptide in a protein.
A
Peptide bonds are formed by hydrolysis.
B
Peptide bonds join the amine group on one amino acid with the R group of another amino acid.
C
Secondary protein structures are caused by hydrogen bonding between atoms of the peptide backbone.
D
Tertiary protein structure emerges when there is more than one polypeptide in a protein.
10
concept
Denatured Proteins & Chaperones
Video duration:
4m
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Video transcript
In this video, we're going to introduce denatured proteins and chaperones. And so what's important for you all to note is that a protein's structure and shape is actually really critical for its proper function. And so what this means is that a protein will not be able to properly function or properly work if it loses or changes its structure and shape. And so it's really the structure and shape that dictates the protein's function. And this idea leads us directly to the term denatured protein, and that is because a denatured protein is a protein that is nonfunctional, a nonfunctional protein that has altered its shape. And so once again, by altering or changing the shape of a protein, that will change its function and make it nonfunctional. Now denatured proteins can result from changes to the environment. And so examples of changes in the environment that could lead to a denatured protein include, examples such as changes in the pH of the solution, changes in the temperature of the environment, or changes in the salt concentration of the environment as well. All of these things can lead to the change of a protein shape and therefore lead to a nonfunctional protein, a denatured protein. Now on the other hand, proteins that have lost their shape can sometimes regain their original shape by the help of what are known as chaperone proteins. Chaperone proteins are proteins themselves that help other proteins reform their original shapes or renature, if you will. And so let's take a look at our example image down below to get a better understanding of denatured proteins and chaperone proteins. And so what you'll need to notice is over here on the left hand side, we're starting with a functional protein, which is this, shape right here, this red structure. And, what's important to note is that it has a very, very specific shape. However, if the functional protein is, heated, if the temperature changes in the environment, recall that the temperature is just one of the changes in the environment that can cause a functional protein to denature and lose its shape. And so if we heat up the protein, that can change the shape of the protein. And so notice here, the protein has changed its shape in comparison to, the functional form of the protein. And so what this means is, of course, we have a denatured protein here that has lost its shape and therefore lost its function. It will no longer work when it's when it's lost its shape. However, proteins can regain their shapes with the help of, other proteins that we call chaperone proteins. And so this structure that you see here, throughout is referring to the chaperone protein. And so the chaperone protein can take the denatured protein and basically help it reform its original structure. And so once the protein has regained its original shape and structure, it becomes a functional protein once again. And so chaperone proteins are good for cells to have to make sure that their proteins are properly folded. And so this here concludes our introduction to denatured proteins and chaperones, and we'll be able to get a little bit of practice applying these concepts as we move forward in our course. So I'll see you all in our next video.