Question

In: Biology

What is the mechanism by which glucose affects the induction of ß-galactosidase by lactose?

What is the mechanism by which glucose affects the induction of ß-galactosidase by lactose?

Solutions

Expert Solution

The metabolism of lactose is under the control of the Lac-operon. An operon is a functioning unit of genomic DNA controlled by a single promoter.

The lac- operon contains genes that code for proteins which transport lactose into the cytoplasm and digesting it into glucose by production of beta- galactosidase. Normally, the lac operon is turned off. The regulatory gene produces the repressor molecule, which binds to the opertor site, preventing transcription.

When lactose is present outside the cell, it crosses the cell membrane and acts as an inducer of the operon. The inducer binds to the repressor forming a repressor-inducer complex which is inactive and now, the repressor do not bind to the operator region. So the RNA polymerase can now transcribe the structural genes. The Lac operon is then transcribed and translated into proteins, facilitating lactose transport into the cell, and its digestion into glucose by the beta-galactosidase enzyme.

How glucose affects this ???

The glucose level in the cell should be low for the above process to occur. When glucose levels are low, the level of  cyclic adenosine monophosphate (cAMP) levels increase. Whenrhe levels of cAMP are sufficient, the cAMP bind and activate another protein, called catabolite activator protein (CAP). CAP now binds to the operon which helps RNA polymerase to attach to the promoter region. This leads to RNA polymerase transcription of genes leading to an increase of lac operon expression.

So, when glucose in the cell is high, there is no CAP protein. So, RNA polymerase cannot bind to the promoter region. So there is no transcription of the Lac operon.


Related Solutions

Describe the process in which glucose affects the induction of ß-galactosidase by lactose.
Describe the process in which glucose affects the induction of ß-galactosidase by lactose.
Does the presence of glucose affects the ability of lactose to induce ß-gal?
Does the presence of glucose affects the ability of lactose to induce ß-gal?
Which genotype will allow the bacteria to make ß-galactosidase (lacZ) in the absence of lactose? (superscripts...
Which genotype will allow the bacteria to make ß-galactosidase (lacZ) in the absence of lactose? (superscripts don't work in this panopto quiz, so check the lecture slide itself) 1) O+Z+/F’O+Z+ 2) O+Z-/F’OCZ+ 3) O+Z+/F’OCZ- B) 1Which genotype will allow the bacteria to make ß-galactosidase (lacZ) in the absence of lactose? 1) I+O+Z+/F’I+O+Z+ 2)I-O+Z-/F’I+O+Z+ 3) I+O+Z-/F’I-O+Z+ 4) I-O+Z+/F’I-O+Z+
. β-Galactosidase (lacZ) has bifunctional activity. It hydrolyzes lactose to galactose and glucose and catalyzes the...
. β-Galactosidase (lacZ) has bifunctional activity. It hydrolyzes lactose to galactose and glucose and catalyzes the intramolecular isomerization of lactose to allolactose. β-Galactosidase promotes the isomerization by means of an acceptor site that binds glucose after its cleavage from lactose and thus delays its exit from the site. Allolactose, not lactose, is the natural inducer for the lac operon. a. Would you expect β-galactosidase to be induced in a zy+ mutant upon the addition of lactose? Upon the addition of...
Please correct if they are wrong Genotype ?-galactosidase Permease Outcome Lactose No lactose Lactose No lactose...
Please correct if they are wrong Genotype ?-galactosidase Permease Outcome Lactose No lactose Lactose No lactose I+P+O+Z-Y-/ I+P+O+Z-Y- + - + - lac+ ISP+OCZ+Y-/ I+P-OCZ-Y+ - - - - lac- I+P+O+Z+/ I+P+O+Z+ + - - - lac+
Lab 6 Beta-Galactosidase Activity (Gene Expression): Preparation 1. When lactose is present and glucose is absent,...
Lab 6 Beta-Galactosidase Activity (Gene Expression): Preparation 1. When lactose is present and glucose is absent, explain what will occur with the lac operon; specifically to the repressor protein, CAP-cAMP complex, RNA polymerase and the production levels of the -galactosidase enzyme 2. When lactose is present and glucose is present, explain what will occur with the lac operon; specifically to the repressor protein, CAP-cAMP complex, RNA polymerase and the production levels of the b-galactosidase enzyme. 3. When lactose is absent...
The lac operon of E. coli encodes the two enzymes ß-Galactosidase and Permease. Indicate in the...
The lac operon of E. coli encodes the two enzymes ß-Galactosidase and Permease. Indicate in the following table whether these enzymes are synthesized (“+”) or not (“–“) given the genotypes in the left column and the presence or absence of the inducer. Note that some of the genotypes are partial diploids, i.e. a second copy of the operon is present on a separate plasmid. Genotype Inducer Absent Inducer Present β-Galactosidase Permease β-Galactosidase Permease a) I+P+O+Z+Y+ b) I+P+O+Z–Y+ c) I+P+O+Z+Y– d)...
Growth condition 1: +glucose & +lactose Growth condition 2: +glucose & -lactose Growth condition 3: -glucose...
Growth condition 1: +glucose & +lactose Growth condition 2: +glucose & -lactose Growth condition 3: -glucose & +lactose In which of the above conditions would you see a change in lac operon expression if you mutate the cAMP receptor protein in E. coli so that it no longer can bind to cAMP? In which direction would the change occur? Group of answer choices Condition 1; Increase. Condition 2; Increase. Condition 1; Decrease. Condition 3; Decrease.
Draw and/or discuss how the Lactose OPERON in bacteria. Include conditions such as no glucose, glucose...
Draw and/or discuss how the Lactose OPERON in bacteria. Include conditions such as no glucose, glucose and low lactose, lactose high and glucose low
3. Explain what happens to the Lac operon when lactose is present and glucose is also...
3. Explain what happens to the Lac operon when lactose is present and glucose is also present. Then explain what happens when lactose is present but glucose is absent. In your answer, include all of the components of the Lac operon and the molecules involved in its regulation. What is the protein product of the Lac operon? Explain why this mechanism of control is adaptive.
ADVERTISEMENT
ADVERTISEMENT
ADVERTISEMENT