This question has 5 parts. PlEASE TYPE your answer which covers all part. A) Wha
ID: 258295 • Letter: T
Question
This question has 5 parts. PlEASE TYPE your answer which covers all part.
A) What traits does the Lac Operon code for AND When would the lac operon in E. coli be repressed and why?
In Figure 7.24 Diauxic Growth Curve of E. coli Growing in a Medium Containing Glucose and Lactose. Cells preferentially use glucose. Only When the supply of glucose is used up do the cells start metabolizing lactose. Note that the growth on lactose is slower than it is on glucose.
B) Why does bacterial growth stop temporarily when the glucose supply in the medium is used up?
C) Why would it be advantageous for a cell to use glucose before lactose?
D) In which conditions would the LacOperon be “turned on.”
High Glucose, Low Lactose
High Glucose, High Lactose
Low Glucose, Low Lactose
Low Glucose, High Lactose
E )How are repressors, activators, and inducer exclusion all involved in the regulation of the Lac Operon
Explanation / Answer
A. Lac operon contains three structural genes that code for the metabolism of lactose.
Lac Z = Beta-galactosidase
Lac Y = Permease
Lac A = Transacetylase
It also contains an operator and a promoter.
B. There is a small lag phase when switching between primary energy source to the secondary energy source in a diauxic growth curve. This lag phase is required to synthesize all the necessary factors required for the metabolism of the alternative energy source.
C. Glucose is the primary energy source of E coli. The enzymes required for glucose metabolism are constitutively expressed. On the other hand, lactose is an alternate energy source. Enzymes required for lactose metabolism are expressed only when lactose is abundant in the environment (provided that glucose is absent). Since the enzymes required for glucose metabolism are always present in the cell, it is advantageous for the cell to utilize glucose first as utilization of lactose requires the synthesis of new factors.
D. Option D is correct.
Lac operon is induced when glucose is absent and lactose is present.
E. Repressor protein binds to the operator when lactose is absent. This excludes the RNA polymerase from binding to the operator. When lactose is present, it binds to the repressor protein and prevents its binding to the operator. Now, RNA polymerase can freely bind to the promoter and transcribe the structural genes. CAP ensures that operon is active only when glucose is absent.
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