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---|CRP|-------------| O |---| Z | Y | A |---
CRP: Binding site for activator
O: Operator, binding site for repressor
Coding sequences:
Z: b-galactosidase
Y: lactose permease
A: thiogalactoside transacetlyase
Wiki User
∙ 12y ago
Wiki User
∙ 12y agoOkay, pay attention because this is going to get weird.
The lac operon has several main components. There is a repressor (LacI), an operator (LacO) several enzyme genes (LacZ, LacY and LacA ) a promoter (Lac P) and a terminator. The repressor is constitutive, meaning it is always made and bound (the lac operon does not function normally, because under normal conditions we don't need to metabolize lactose, we use glucose instead). When glucose levels go down and lactose is consumed two things happen. Firstly, the lac repressor binds a molecule of lactose and falls off the operator, meaning the operon can now be turned on. Secondly, levels of cAMP rise, meaning that something called the CAP (catabolite activator protein) binds to the operon and facilitates transcription (makes the operon more likely to be transcribed into mRNA). Once the repressor falls off and CAP is bound the RNA polymerases can attach to the promoter and transcribe the operon into mRNA. This mRNA is then translated into the enzymes that digest lactose.
The main concept: We don't need to digest lactose when glucose is present so the operon is always repressed by a repressor. When lactose is present the repressor binds lactose and falls off. When glucose is not present (remember, we prefer glucose) CAP binds to the operon to make it more likely to be transcribed. It is then transcribed into mRNA, which is translated into enzymes needed to digest lactose. I'm sorry if that was complicated, but the lac operon is hard to explain.
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When does the induction of the lac operon occur?
The lac operon is most active when glucose levels are low and lactose is present.
The lac operon enables a bacterium to build the proteins needed for lactose metabolism only when?
Lactose is present, otherwise the lac operon is not needed and is shut off.
The lac operon is shut off when what is absent?
Lactose is absent
Four of the five answers listed below are features of the lactose operon Select the exception a regulator b terminator c operator d promoter e structural gene?
The "lac operon" is the unit of DNA in E.coli and other bacteria which is responsible for the metabolism of lactose. So with regards to the question above, its function is that of an operator.
What environmental factor causes the lac operon to turn on?
In the lac operon model, lactose acts as in inducer molecule. In the presence of lactose, the molecule binds to the repressor protein. This repressor-lactose complex is unable to bind to the promoter. When the promoter is not occupied, RNA pol - II binds to it and begins transcribing the structural genes located downstream. Thus, the lac operon is turned on in the presence of lactose.
The operon that controls the metabolism of lactose is called the what?
its an operon required for the transport and metabolism of lactose.
When does the induction of the lac operon occur?
The lac operon is most active when glucose levels are low and lactose is present.
The positive control of the lactose operon in bacteria is what?
Catabolite repression is the positive control of the lactose operon in bacteria. Glucose is metabolized initially and when depleted, the lactose.
The obvious advantage of the lactose operon system is that?
lactose metabolizing enzymes need not be made when lactose is not present.
The lac operon enables a bacterium to build the proteins needed for lactose metabolism only when?
Lactose is present, otherwise the lac operon is not needed and is shut off.
What happen to lac repressor in E. coli when lactose is present?
E. coli binds with lactose which changes its conformation so that it no longer binds to DNA. This allows the lactose operon to be transcribed.
When is lac operon most active?
The lac operon is most active when glucose levels are low and lactose is present.
Lactose in take in E. coli?
it is by lac operon syastem
The lac operon is shut off when what is absent?
Lactose is absent
How does lactose cause the lac operon to turn on?
The lac repressor protein has a binding site for lactose itself.
Four of the five answers listed below are features of the lactose operon Select the exception a regulator b terminator c operator d promoter e structural gene?
The "lac operon" is the unit of DNA in E.coli and other bacteria which is responsible for the metabolism of lactose. So with regards to the question above, its function is that of an operator.
Where on the lac operon does transcription take place?
The lac operon encodes enzymes required in the digestion and transport of lactose. Transcription is activated when there is lactose in the cellular environment, and RNA polymerase binds to the promoter region of the operon, and activates the expression of lacA, lacZ and lacY.
