702061
Description
Mind Map by Sophie Barrett, updated more than 1 year ago
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Created by Sophie Barrett
over 10 years ago
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Lac Operon
- The product of the Lac Z gene =
beta-galactosidase. It cleaves lactose
into glucose and galactose
- The product of the Lac Y gene
= lactase permease. It
transports lactose into the cell
- The product of the Lac A gene =
beta-galactoside transacetylase. It is
also involved in lactose hydrolysis
- LACTOSE ABSENT
- The path of RNA
polymerase is
blocked
- transcription of the Lac genes
cannot occur
- saves energy, there is
no need to have the
proteins since lactose is
not present
- Only a few Lac enzymes remain in the cell, but these are crucial
- saves energy, there is
no need to have the
proteins since lactose is
not present
- transcription of the Lac genes
cannot occur
- The path of RNA
polymerase is
blocked
- LACTOSE PRESENT
- The few Lac enzymes present allow the
lactose to be taken up into the cell
- These few lactose disaccharide
molecules are metabolised
- One intermediate is allolatose
- Allolatose, an isomer of lactose,
acts as an inducer
- Binds to the lactose repressor
- Changes it's confirmation
- Lactose repressor can no longer
bind to the operator
- The path of RNA Polymerase is no
longer blocked
- Transcription of the Lac genes
commences
- Uptake and Metabolism of
Lactose from the
environment
- So allactose acts an indicator of the presence of the
lactose
- Uptake and Metabolism of
Lactose from the
environment
- Transcription of the Lac genes
commences
- The path of RNA Polymerase is no
longer blocked
- Lactose repressor can no longer
bind to the operator
- Changes it's confirmation
- Binds to the lactose repressor
- Allolatose, an isomer of lactose,
acts as an inducer
- One intermediate is allolatose
- These few lactose disaccharide
molecules are metabolised
- The few Lac enzymes present allow the
lactose to be taken up into the cell
- But, if glucose if present, the cell will use it preferentially.
- The cell uses a Catacolic Activator Protein (CAP) to detect available glucose
- CAP binds to DNA upstream of the lac promoter
- This enhances the binding of RNA Polymerase, increasing transcription
- But, it can CAP can
only bind in the
presence of cAMP
- cAMP levels are
influenced by glucose
conentration
- How?
- Adenylyl cyclase cataylses
the formation of cAMP and
is inhibited by glucose
- Adenylyl cyclase cataylses
the formation of cAMP and
is inhibited by glucose
- How?
- cAMP levels are
influenced by glucose
conentration
- This enhances the binding of RNA Polymerase, increasing transcription
- CAP binds to DNA upstream of the lac promoter
- The cell uses a Catacolic Activator Protein (CAP) to detect available glucose
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