Question

e. coli are grown on a medium containing lactose. once glucose is added to the medium, the bacteria stop fermenting lactose

Answer 1

The lac operon is an operon required for the transport and metabolism of lactose in E.coli. When lactose is introduced to the increased medium, the lac genes are expressed due to the fact allolactose binds to the Lac repressor protein and maintains it from binding to the lac operator. Allolactose is an isomer of lactose. Small quantities of allolactose are shaped when lactose enters into E. coli. allolactose binds to the repressor protein and reasons the conformational change. As a result of this, the repressor can no longer bind to the operator area and falls off. RNA polymerase can then bind to the promoter and transcribe the lac genes. After some time, when the level of lactose decreases as it is metabolized using enzymes, it causes the synthesis of the repressor from the regulator gene. This repressor binds to the operator gene and prevents RNA polymerase from transcribing the operon and the transcription is stopped. This type of law is acknowledged as negative regulation.

Allolactose is a disaccharide comparable to lactose. It consists of the monosaccharides D-galactose and D-glucose linked thru a β1-6 glycosidic linkage alternatively of the β1-4 linkage of lactose. It may additionally occur from the occasional transglycosylation of lactose through β-galactosidase.

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