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. translation

Mechanism by which the presence of glucose inhibits the lac operon.

Accepted Answer

Hi, everybody. Welcome back. Let's look at the next problem. It says if both glucose and lactose are present in the environment of an E coli, the production of beta galactosidase will be a doubled B inhibited C raised exponentially or D none of the above. So let's recall what beta galactic does an enzyme involved in the metabolism of lactose and its expression is controlled by the lac opera. So we can recall that glucose is the preferred energy source for E coli, it has a higher energy yield. But E coli can use lactose as an alternative source when there is no glucose present. So the system of the lac operon is a system of what's called catabolite repression, which we can recall is the inhibition of the synthesis of enzymes that are involved in the catabolism of alternate energy sources. So, since lactose is an alternate, alternate energy source, this lac operon in its symptom of catabolite repression controls the expression of the enzymes involved in lactose metabolism. So they serve two purposes so that A when glucose is around, you aren't metabolizing lactose, you want the cell to use up the glucose first and then B if lactose is absent, you're not wasting time making these enzymes since they've got nothing to work on. So there's kind of two parts there. So in this situation, we're talking about both glucose and lactose are present, lactose is present. So you don't want to prevent the synthesis of these enzymes that digest lactose. The lac operon is a an inducible opera and that means it's repressed as its standard state. But when lactose is, is present, that repression is lifted and the genes are expressed. So it's induced when lactose is present, which is the case. So we don't have a case of specific repression per se. However, we also have glucose present. So we want the cell to preferentially metabolize glucose. So the mechanism for that is one in which the expression of these enzymes that metabolize lactose is inhibited. It's not repressed, it's not prevented altogether, but it's prevented from operating at full efficiency. And one of those enzymes is of course beta gal lacto. So when glucose and lactose are present in E coli or in the environment in e coli, the production of beta gal lactoses will be inhibited, which is choice B when we look at our other answer, choices doubled, raised exponentially. That's obviously gonna be the opposite situation. The synthesis of those enzymes is increased by quite a bit when glucose is absent. So in glucose is absent, levels of the molecule C A MP rise in the South. This binds to a protein called cap cap binds to a, the activated cap binds to a cat binding site on the lac operon that increases the ability of RN A polymerase to bind to the promoter. And this turns up the production of those lack metabolizing enzymes by quite a lot. But that increase in synthesis only occurs when glucose is absent. So choice, a double choice c raised exponentially are not our correct answer that would only occur if glucose were absent. And choice D none of the above is not correct. Because when glucose is present, the synthesis of those enzymes including beta galactosidase is inhibited due to this system of catabolite repression. So again, not true repression in the sense of a repressor protein binding to the operator. But an overall level of just turning down the expression of these alternate energy source enzymes. See you 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. translation

Mechanism by which the presence of glucose inhibits the lac operon.

Watch next

Glucose's Impact on Lac Operon practice set

Struggling with Microbiology?

Use the following choices to answer questions 7 and 8:a. catabolite repressionb. DNA polymerasec. inductiond. repressione. translationMechanism by which the presence of glucose inhibits the lac operon.

Watch next

Glucose's Impact on 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. translation

Mechanism by which the presence of glucose inhibits the lac operon.