So proteins are a very heavy topic in biochemistry, and we'll talk a lot of details about proteins later on in our course. Now in this video, we're gonna do a quick recap on proteins. So recall that proteins are one of 4 major biological macromolecules that all cells have. And proteins have vast structural and functional roles. So, we've seen that in our previous bio courses where proteins do so many different things for a cell, and we'll see that in this course too. So proteins are the polymers of amino acid monomers. So all that means is that the monomers of proteins are amino acids. And similar to nucleic acids, proteins have directionality. And all that means is that in a chain of a protein, the ends of that protein are chemically different from one another. And so proteins have an n terminal end and a c terminal end on the opposite end. And so the n in the n terminal refers to the presence of a free amino group. And recall that amino groups have a nitrogen atom in them, which is represented by an n. And on the other hand, a c group. And so the c in c terminal refers to the carboxyl group. So let's take a look at our example. And down here, what we'll see is that we have a bunch of amino acid monomers represented by triangles, and these triangles are different colors. So these are different amino acids. And through a process, we can link all of these amino acids together in a chain to create a protein polymer. So in the So in the next video, what we're gonna talk about is the amino acid itself. What is this monomer and what are the components? So I'll see you guys in that video.
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concept
Amino Acids
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2m
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So now that we've refreshed our memories that amino acids are the monomers of proteins, we can now focus on the structure of the amino acid itself. And recall that each amino acid contains common components as well as a unique r group. And living organisms use a total of 20 different amino acids that can be grouped together based off of the properties of their R groups. And so in our example below, what we see is that this box shows the amino acid components. And the ones that are bracketed in red are common to all amino acids, whereas the unique components like the R groups are shown below. So the common amino acid components include a central carbon atom, also known as an alpha carbon shown here in the amino acid structure. It also includes a central hydrogen atom shown above, an amino group on the n terminal end of the amino acid shown here, and a carboxyl group shown on the opposite end of the amino acid on the c terminal end, shown here. And so the shaded portions that I've just highlighted again are common to all amino acids, so the unique parts are shown by the r groups. And over here, we have a table of the amino acids and their R groups. And notice that I've intentionally made this table kind of small and difficult to read because we're not so interested in the details just yet. We'll talk about all the details of the amino acids in our later videos. For now, I just want you guys to notice that, each of the amino acid contain a different r group, and you can see that because the r groups are highlighted in blue and the blue boxes are all different sizes. And so, these amino acids, you can also see are grouped together based off of their properties, and you can see that by the boxes which are grouping amino acids together. And so in our next video, what we're gonna talk about is how amino acids come together to create the different levels of protein structure. So I'll see you guys in that video.
3
concept
Protein Structure & Terms
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3m
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In this video, we're actually gonna do 2 different things. The first is, we're gonna recap the protein levels of structure, and the second, we're going to define several different protein related terms that tend to confuse students. And so for the first one, recall that proteins can have up to 4 levels of structure, and they are conveniently called primary, secondary, tertiary, and quaternary levels of structure. And again, in this video, we're just gonna do a quick recap, but later on in our course, we're gonna dive into a lot more detail for each of these levels of structure. Now, for the second, objective, there are several different terms that refer to amino acid chains that vary in length, and so you can have short, intermediate, and longer chains, and these terms include oligopeptide, peptide, polypeptide, and protein. And so in our example below, we'll first consider the protein levels of structure and then we'll define and distinguish between each of these terms. And so, for the first level of protein structure, recall that it is the primary level of structure. And this refers to the types, the quantity, and the order of amino acids from the n terminal end of a protein to the c terminal end of a protein. And the primary level of protein structure is incredibly relevant because it dictates and influences all the other levels of structure. Now recall that the secondary level of structure is the formation of alpha helices and beta pleated sheets. And so recall that alpha helices are a winding type of structure and beta pleated sheets are a zigzag or a staircase type of structure. Now, the 3rd level of structure is tertiary protein structure, and notice that this includes beta pleated sheets and alpha helices, but it's really referring to the overall three-dimensional shape of that protein. Now, quaternary protein structure refers to a protein that has multiple amino acid chains, and we can see that in this diagram where we have a light colored gray chain and a darker colored chain. And these are separate chains that have their own 3 d structure and they complex together to form a single protein with multiple subunits. And every protein has primary, secondary, and tertiary levels of structure. However, not all proteins contain quaternary levels of structure. Now, for our second objective of this video, we're gonna define these terms. And so oligopeptide refers to an amino acid chain that contains between 220 amino acids. Peptide refers to amino acid chains that contain less than 50 amino acids. So you can see that there's some overlap between peptide and oligopeptide. Now polypeptide refers to amino acid chains that contain greater than 50 amino acids and proteins can contain up to from 100 up to several thousands of amino acids. And so notice there's some overlap between protein and polypeptide. Now really the main difference between polypeptide and protein is that polypeptide tends to refer to just the chain of amino acids, whereas protein refers to the chain of amino acids, but in its functional form. And so proteins include the functional form. And so in our next video, we're gonna talk about a very specific type of protein and that's the enzyme. So I'll see you guys in that video.
4
concept
Enzymes
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1m
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Video transcript
In this video, I'm gonna give you guys some quick facts about enzymes. But later on in our course, we'll talk a lot more details about enzymes. Now recall that enzymes are proteins that catalyze chemical reactions or speed up chemical reactions, and they can do so without actually being consumed by the reaction. And the reactants of enzymes are called substrates, and the substrates fit perfectly into an enzyme's active site, and then the enzyme converts the substrate into the products. So let's take a look at our example. And down here what we have are 2 substrates, a red one and a yellow one. And below we have our enzyme, which has an active site, and the substrates fit perfectly into the enzyme's active site to create an enzyme substrate complex. And then the enzyme, induces the reaction and converts the substrates into the product. And it does so without being consumed, which means that the enzyme can go back and repeat the reaction on a new set of substrates. And enzymes are incredibly relevant to all life because enzymes pretty much catalyze every cellular reaction and they make those reactions occur at a rate that's sustainable for life. And so the last thing I wanna leave you with is that the ending a s e is indicative that it is an enzyme. And so for example, peptidase ends in ase and peptidases are indeed enzymes. And again, we'll be talking about enzymes throughout our entire biochemistry course. And so, that concludes our lesson on enzymes and I'll see you in the practice videos.
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Problem
Problem
Which of the following is not a component of an amino acid?
A
Peptide
B
α-carbon
C
Amino group
D
Carboxyl group
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Problem
Problem
Which level of protein structure corresponds to the formation of α-helices and β-pleated sheets?
A
Primary
B
Secondary
C
Tertiary
D
Quaternary
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Problem
Problem
Fill in the blanks: Enzymes __________ chemical reactions _________ being consumed by the reaction.