Use the following choices to answer questions 7 and 8:
a...

Question

Use the following choices to answer questions 7 and 8:

a. catabolite repression

b. DNA polymerase

c. induction

d. repression

e. translatio

The mechanism by which lactose controls the lac operon.

Accepted Answer

Hi, everyone. Welcome back. Our next question says in E Coli lac Operon can only be expressed if a only glucose is available. B both glucose and lactose are available. See, only lactose is available or d neither lactose nor glucose is available. So to think this through, we need to think about the purpose of the regulation provided by the LAC operon. So the lack o run controls the expression of genes involved in lactose metabolism. And of course, lactose is a less preferred energy source since glucose provides a higher yield of energy when it's metabolized. So the cell will want to use glucose when that's available and only turn to lactose when there is no glucose present. So the conditions under which you want lactose expressed. So lactose expressed or excuse me, lactose is the sugar. It gets abused. The conditions under which you want the but black jeans expressed or when glucose is absent. Because if glucose is there, you want the cell using glucose preferentially and when lactose is present because if there is no lactose around to digest, you don't want your cell wasting its resources, synthesizing these enzymes to metabolize it. So we recall that we have this is an inducible operon, which means its normal state is turned off, but it gets essentially turned on. So when lactose is present, we'll say turns on expression by preventing the repressor binding to the operator. So in its normal off status, there's a lac repressor protein bound to the operator that blocks RN a polymerase polymerase from coming in and transcribing the genes. When lactose is present, you have a form of lactose called allo lactose that binds the repressor protein, thereby releasing it from the operator, preventing it from binding to the operating operator. And now RN A polymerase can come in and transcribe those genes. So the other circumstance you want is when glucose is absent, when glucose is absent, you have the build up in the cell of a MO who called C A MP. So C MP levels rise when glucose is absent. Then C A MP and the C A MP molecule binds to a protein called cap cap catabolite activator protein. Once C A MP has bound to cap, that activated cap binds to a cap binding site. And once it's in position, it enhances the ability of R and A polymerase to bind to the promoter. So we'd say turns up expression of those black genes. So without that happening, the lac genes can be expressed but very, very slowly. Once you get this activated protein coming in binding to the binding site, it just turns up the transcription of the genes. So the answer to our question of the lack of one can only be expressed if the conditions we're looking for are choice. C only lactose is available. So we look at other answer. Choices. Choice. A only glucose is available. Well, when there's no lactose, the operon is repressed because there's no lactose. So that's not our answer. Choice in choice. B both glucose and lactose are available. If glucose is available as we discussed, there's no C A MP. So the transcription is inhibited. Basically, we'd say so it's not turned off completely with a repressor. But because RN a polymerase can't bind as well, it's very, very inhibited from happening at a reasonable rate. So choice B is not correct. And in choice D, neither lactose nor glucose is available. Again, in the absence of lactose, the oon is repressed so that Brons repressed without lactose. So that's why choice D is incorrect. So once more in E coli, the Lac Aron can only be expressed if choice C only lactose is available. See you in the next video.

Struggling with Microbiology?

Use the following choices to answer questions 7 and 8:
a. catabolite repression
b. DNA polymerase
c. induction
d. repression
e. translatio

The mechanism by which lactose controls the lac operon.

Watch next

The Lac Operon practice set

Struggling with Microbiology?

Use the following choices to answer questions 7 and 8:a. catabolite repressionb. DNA polymerasec. inductiond. repressione. translatioThe mechanism by which lactose controls the lac operon.

Watch next

The Lac Operon practice set

Use the following choices to answer questions 7 and 8:
a. catabolite repression
b. DNA polymerase
c. induction
d. repression
e. translatio

The mechanism by which lactose controls the lac operon.