The Lac Operon - Video Tutorials & Practice Problems
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1
concept
The Lac Operon
Video duration:
7m
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in this video, we're going to begin our lesson on the lack opera. And so the lack opera is actually an induce a ble opera, which means that it is normally turned off, but it can be turned on or it can be induced. And that's why it's called an induced herbal opera. And it actually has three different genes that encode enzymes that are responsible for metabolizing lactose for energy. And so lactose is a sugar. It is a carbohydrate that can serve as an energy source. But before lactose can serve as an energy source, it requires these specific enzymes to be expressed, and these enzymes again are going to metabolize lactose for energy. Now you can see that the lack Oberon gets its name lack because it's important for metabolizing lactose. And so the lack and lactose is the lack and lack opera. Now, these three genes that are encoded within the lack opera include number one lack Z number two lack Y and number three lack A. And so each of these genes, like Z like wine like A and code an enzyme, and those enzymes are all related to one another because they're all important for metabolizing lactose for energy. And so if we take a look at our image down below, which you'll notice is over here on the right, we're showing you the lack opera and again recall operations are a group or a set of related genes, all controlled by a single promoters, so you can see the lack promoters over here and also notice that there is the lack operator right here, and so lack Z lack y and lack A are the three genes that are in the lack opera and are all related to lactose metabolism. And so these three genes lacks the lack y and like they would need to be transcribed into an M R N a and then translated into their appropriate enzymes their appropriate proteins before, uh, they can be used to metabolize lactose. However, what's really important to remember is that transcription and translation actually requires a lot of energy, and so the cell does not want to waste energy and so, therefore, sells only want to express lack opera in jeans when those genes are needed. However, if those genes are not needed, then the cell does not want to be performing transcription and translation because it requires a lot of energy. And so basically what this means is that the lack opera on needs to be under regulatory control, where it needs to be able to be turned off and turned on under the right conditions when these genes are needed and when they're not needed. And so it's important to note is that there is going to be a repressor protein with this lack opera, and the active repressor protein is referred to as lack I mhm and so lack I is the active repressor protein and, uh, normally lack. I is going to be in its active state. And so the active repressor protein lack. I is going to repress transcription as a repressor protein should. And so normally the active repressor lack. I is going to repress transcription, and that is why the lack opera is normally going to be turned off. And, of course, the lack I active repressor protein is going to bind or be bound to the lack operator. And so if we take a look at our image down below, which will notice is over here on the left hand side, we're showing you the lack regulatory gene. And so here we have the lack hygiene and the lack. I gene has its own promoter, and so the lack I gene will be transcribed and translated into an active lack repressor, which is a repressor protein. And so this active lack repressor is going to bind to the lack operator right here and when it's bound to the lack operator as repressor proteins. Should they repress transcription, they block transcription. They prevent the RNA preliminaries from proceeding forward and transcribing these jeans. And so under normal conditions. This is what we tend to see is that the active lack repressor is made, and the active lack repressor blocks transcription of these genes. So this opera and the lack opera is normally turned off. However, under the right conditions, the lack opera and can be turned on it can be induced. And that is why we call it an induced herbal opera in because it's normally off. But it can be turned on, it can be induced, and so it's only going to the lack. Opera is only going to be transcribed only in the presence of lactose number one, but also in the absence of glucose. And so these are two ideas. The presence and absence of lactose and the presence and absence of glucose that we're going to look at these two ideas, these two scenarios and determine how is it that it impacts lack operation transcription. But what's important to note here is that the lack opera and will only be turned on and the presence of lactose and in the absence of glucose. And we'll talk about why that is, as we move forward in our course. And so the lack, opera and recall black operations and operations in general are associated with pro carry Arctic organisms and E. Coli. Escherichia coli is a bacteria, uh, and so the lack opera and E. Coli is how this lack opera was first discovered. And so that is the context that we're going to be looking at, the lack opera in and so the lack opera on an E. Coli. It contains a single promoter, the lack promoter and three genes required for lactose metabolism. And those three genes are like Z like y and lack. And so this here concludes our brief introduction to the lack opera, and once again, as we move forward in our course. We're going to continue to talk about the lack opera and how it works, so I'll see you all in our next video.
2
Problem
Problem
The protein that binds to the operator of the lac operon to prevent transcription is encoded by which gene?
A
lac I.
B
lac Y.
C
lac A.
D
lac Z.
3
Problem
Problem
The lac operon is a(n) _______________ operon that is typically ______________.
A
inducible; induced.
B
repressible; repressed.
C
inducible; repressed.
D
repressed; inducible.
4
concept
In the Absence of Lactose
Video duration:
4m
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in this video, we're going to continue to talk about the lack Opteron, specifically in the absence of lactose. And so before we even move on here, recall from our previous lesson videos that the lack opera is only going to be on or expressed when those genes are needed, and recall that those genes in the lack opera lack Z like y and like a there needed to metabolize lactose and break it down in order to get energy from it. However, if lactose is absent, if there is no lactose in the environment, and that means that those genes in the lack opera are not really needed because there's no lactose for those genes to break down. And so we can imagine that this means that the lack of operas would be off or inactive in the absence of lactose. And that's exactly what we're going to see here. And so when lactose is not available to metabolize because it's not available in the environment, then the repressor protein lack. I is going to repress the expression of the genes in the lack opera and so lack I this repressor protein it's going to bind to the lack operator and block RNA preliminaries, which recalls the enzyme that is responsible for transcription. Uh, and so it's going to block RNA preliminaries and prevent RNA polymerase from initiating transcription. And so there will be no transcription because it is being blocked and inhibited. And so if we take a look at our image down below, we can get a better understanding of the lack opera in the absence of lactose. And so, in the absence of lactose, the repressor protein lack, I is going to be active. And because it's active, it's going to bind to the operator and block transcription, preventing transcription and turning off the opera in the absence of lactose. And so here, taking a look at this image again, we're focusing on the lack opera in the absence in the absence of lactose, so there's no lactose available in the environment. And so, taking a look here at our image noticed we've got our lack opera on over here, and we've got the lack regulatory gene over here, which has the lack I gene with its own promoter and, of course, the lack I gene with its own promoter. It is going to be transcribed and translated. And in the absence of lactose, uh, the lack I repressor protein is going to be active. So here we have an active lack repressor, And so because it is a repressor and it is active, it is going to bind to the operator here, and so you can see that the active lack I repressor is binding to the operator. And when it binds to the lack operator, as we mentioned up above in the text, it's going to block RNA preliminaries and prevent RNA preliminaries from binding and initiating transcription. And so transcription of these genes is not going to occur because, uh, the lack I repressor is bound and blocking. Um, the RNA preliminaries in the absence of lactose. And this is a good thing for the cell, because when there is no lactose available when the lactose is absent, then the cell has no need to express these genes because these jeans are all involved with breaking down lactose. But there is no lactose, so it's not going to waste energy in producing the products of these genes. And so this is why, in the absence of lactose, the lack opera is off or inactive and will not be expressed. And so this year concludes our introduction to what happens when the black operation is in the absence of lactose, and as we move forward, we'll be able to talk about the lack opera in the presence of lactose, So I'll see you all in that video.
5
concept
In the Presence of Lactose
Video duration:
3m
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So now that we know from our last lesson video that in the absence of lactose, the lack opera is off or inactive in this video, we're going to talk about the lack opera and but in the presence of lactose. And so when lactose is readily available to metabolize in the environment, lactose can actually act as an inducer molecule in the lack operas. And so really, it turns out that a derivative of lactose that's called a low lactose uh, you may or may not be responsible for knowing Allah lactose, uh, but a derivative of lactose, uh, is going to bind and inactivate the repressor protein lack I. And so if black eye is inactivated, then that means that it will not. It cannot bind to the operator. And if it cannot bind to the operator, that means that RNA preliminaries will be allowed to initiate transcription of the lack operas, and so that will turn on the lack opera. And so if we take a look at our image down below notice, we're saying in the presence of lactose, when lactose is readily available to metabolize, then lack I. The repressor protein is going to be inactive. And if it's inactive, that's going to allow for lack operation transcription, turning on the lack opera. And so here, again in the title, were saying that the lack opera uh, we're focusing on the lack opera in the presence of lactose. And so this is our molecule to represent lactose. And so notice over here we have again our lack regulatory gene lack I with its own promoter here and lack I is going to be transcribed and translated into the lack. Repressor, however, notice that in the presence of lactose, a derivative of lactose will be able to bind to the lack of repressor and inactivate the lack repressor. And so notice that the lack repressor here has changed its confirmation. And now it is no longer able to bind to the lack operator and block transcription. And so because the inactive lack repressor cannot bind to the operator, this allows RNA preliminaries to bind to the lack promoter and initiate transcription of these lack Oberon genes like Z lack y and lack a and so, of course, it's going to create an M RNA strand, and the M RNA Strand is going to have a stark code on here for each of the genes within it. And ultimately this M R and A is going to be translated. And when it's translated, it's going to be, uh, converted into these enzymes. And these enzymes will be able to break down lactose and so they can go over here and break down lactose and use lactose as an energy source. And so, ultimately, what we're seeing here is that the lack opera is really only going to be on or active in the presence of lactose when lactose is available. And that allows, uh, the genes to be turned on when they are needed. And so this year concludes our brief introduction to the lack opera in the presence of lactose, and we'll be able to get some practice applying the concepts that we've learned as we move forward in our course. And then we'll also get to talk about how glucose will also impact expression of the lack opera. So we'll talk more about that as we move forward. So I'll see you all in our next video
6
Problem
Problem
In the lac operon, which of the following functions does the lactose molecule serve:
A
It is the corepressor molecule.
B
It is the repressor molecule.
C
It is the inducer molecule.
D
It serves no function in regulating the lac operon.
7
Problem
Problem
If E. coli bacteria are grown in the presence of lactose:
A
The repressor will bind the operator allowing transcription of the lac operon genes.
B
The repressor will not bind the operator preventing transcription of the lac operon genes.
C
The repressor will not bind the operator allowing transcription of the lac operon genes.
D
The repressor will bind the operator preventing transcription of the lac operon genes.
