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21 Cards in this Set

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Catobolic pathway
molecule is broken down, for energy or components
- ex. sugar metabolism and fat breakdown
What is the name of the molecule being broken down?
Catabolyte
What is an anabolic pathway?
When build up of product from components is seen
- ex. amino acid synthesis and nucleotide synthesis
The Lac Operon
-Polycistronic RNA, or one MRNA with 3 genes on it
-All needed to metabolize lactose
- B-galactosidase, permease, and Transacetylase
E. Coli and lactose
-E. Coli preferentially uses glucose for energy
-If glucose is present, it won't use other sugars
-Will shift to other sugars like lactose or arabinose when no glucose present
Expression of lac operon in response to lactose is decreased when lactose is removed
b-galactosidase activity can be easily measured
What is an Operon?
Unit under transcriptional control of operator
What is an Operator?
DNA sequence bound by a repressor that regulates transcription
What is a Repressor?
Protein that inhibits transcription
What is an Apaprotein?
protein that can bind a small molecule when athe small molecule is not bound
lac operon model
-Repressor gene
-promoter of repressor protein
-operator
-Structeral genes
Mechanism of Lac operon regulation
Repressor is normally bound to the operator, preventing transcription
Presence of lactose leads to allolactose. Allolactose binds to the repressor and makes it fall off the operator
With no repressor bound, transcription can proceed and the lac genes are transcribed
Mechanism of CRP activation
-CRP binds to cyclic AMP, produced when glucose is low
-CRP+cAMP binds to CRP response element on DNA
- -35 box of CRP-activated promoters is very weak
- alpha subunit of polymerase contacts CRP, makin gup for weak -35 box and enhancing trtanscription
E. Coli lac operon requires what?
CRP
gal Operon is subjecto to what type of regulation?
Negative and Positive
What causes DNA looping and repression of the gal operon?
Gal repressor and HU
-gal repressor binds to Operators
-HU loops promoter around itself
CRP-RNA polymerase interactions at class II cAMP-dependant promoters
Arabinose operon
-Similar to lactose
-Uses Ara repressor for negative regulation and CRP for positive regulation
-Difference is how binding of arabinose affects repressor
-Operator is seperated into three regions
araBAD promoter region has multiple regulatory elements
yes
AraC undergoes a conformation change when?
After binding arabinose to araC dimer (repressor)