2959105
Description
Flashcards by Olivia Hocking, updated more than 1 year ago
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Created by Olivia Hocking
over 9 years ago
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| Question | Answer |
| What is the main function of the Lac Operon? | It produces the enzymes needed to convert Lactose into Glucose when Glucose is absent |
| What is the role of B-Galactosidase? | It hydrolyses lactose to galactose and glucose |
| In the presence of Glucose, what happens to B-Galactosidase? | The level of the enzyme is low as it is not needed |
| What happens to B-Galactosiade when Glucose levels are low? | The level of B-Galactosidase increases |
| What happens to B-Galactosidase when lactose levels are high? | The level of B-Galactosidase increases |
| Why is B-Galactosidase referred to as an inducible enzyme? | It's function can be decreased or increased depending on levels of glucose and lactose |
| How is lactose converted into galactose and glucose? | Lactose is hydrolysed by B-galactosidase into galactose and glucose |
| Apart from B-Galactosidase, what other 2 enzymes are synthesized? | Galactosidase ermease and thiogalactosidase transacetylase |
| What is the role of galactosidase permease? | It is required for the transport of lactose across the cell membrane |
| What is the role of thiogalactoside transacetylase? | It's function is unknown - it is not essential for lactose metabolism |
| What are the 3 structural genes involved in lactose metabolism? | B-Galactosidase, thiogalactoside transacetylase, galactosidase permease |
| What are the genetic elements of the lac operon? | Regulatory gene (i), operator site, structural genes |
| What is the promoter site on the lac operon? | It's where the RNA polymerase binds |
| What is a repressor protein and what does it do? | It's something that blocks the transcription of genes - it binds tightly to the operator in the absence of lactose |
| In the presence of lactose, what happens to the repressor? | Lactose (an inducer) binds to the repressor protein causing a conformational shape change and the repressor dissociates from the operator - allowing RNA polymerase to copy the genes and produce an mRNA transcript |
| Where does the repressor bind when glucose is high? | To the operator |
| Where does RNA polymerase bind to? | The promoter |
| In the presence of glucose, what happens on the repressor? | Repressor protein produced by a regulatory gene binds to the operator which prevents RNA polymerase to transcribe the lac operon |
| Describe how cAMP is made? | PPi (pyrosphosphate) is phosphorylated from ATP by adenylate cyclase which gives cAMP |
| What is adenylate cyclase? | The enzyme that phosphorylates ATP to cAMP |
| When the level of glucose drops, the level of cAMP rises through the action of what enzyme? | adenylate cyclase |
| What is the role of CAP? | It binds to the promoter region, stimulating initiation of lac mRNA synthesis |
| How does CAP bind to the promoter region? | When cAMP is produced, it binds to CAP and then the affinity of CAP for DNA increases and therefore it binds to the promoter region |
| Summarise what happens to the levels of everything involved in the lac operon if lactose is high? | Lactose is high Glucose is low cAMP is high CAP is high 3 genes are high - B-galactosidase, transacetylase and permease |
| Summarise what happens to the levels of everything involved in the lac operon if glucose is high? | Glucose is high Lactose is low cAMP is low CAP is low 3 genes are low: B-galactosidase, transacetylase, permease |
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