Lecture 16 - Regulation Flashcards
What is an example of short term regulation?
Feedback inhibition (and activation)
What is an example of post-translational control?
Protein kinase and protein phosphatase in glycogen metabolism control by covalent modification (+/- phosphate)
What is an example of long term control?
Control of RNA and protein levels because the response time is longer
What is an example of compartmentation regulation?
Beta-oxidation occurs inside the mitochondria, whereas fatty acid synthesis occurs in the cytoplasm
What is an example of hormonal regulation?
Glycogen regulation
How are branched pathways regulated?
1) Multiple enzyme control
2) Sequential control
3) Synergistic feedback
Describe multiple enzyme control
Multiple alleles of the same enzyme (1 and 2) catalyze a step early in the pathway, and are affected differently by different inhibitors (E and G)
What is the problem with multiple enzyme control?
Additional sites of control are required in each branch after the initial branch point
Describe sequential control
The end products inhibit a step after the branch, which causes a build-up of an intermediate, which in turn acts sequentially to inhibit a step earlier in the pathway
Describe synergistic feedback
- 2 end products work synergistically to inhibit a step early in the pathway and together have a much larger effect than individually
- Can be cumulative (effects of E and G are additive) or concerted (neither has an effect individually)
What does control of transcription affect?
The number of mRNA molecules produced, thereby affecting the number of protein (enzyme) molecules produced
Is transcriptional control common? Why or why not?
Yes because it provides greater energy efficiency in stopping both RNA and protein synthesis
What is an operon?
A grouping of genes, the products of which have a common metabolic purpose
What is the function of lac operon?
Metabolism of lactose (galactose-beta1,4-glucose)
What does lac operon encode?
- Transport protein (lactose permease) to transport lactose into the cell
- Cleavage enzyme (beta-galactosidase) to cleave the 2 sugars
- Beta-galactoside transacetylase for detoxification
Which reactions does beta-galactosidase catalyze?
1) Lactose galactose + glucose
2) Galactose + glucose allolactose
What affects the synthesis of beta-galactosidase mRNA?
The carbon sources present in the growth medium
When is beta-galactosidase produced?
When substrate is present
Is lac operon produced when succinate is present?
No
Is lac operon activated when lactose is present?
Yes, to digest the lactose
Is lac operon activated when glucose is added?
No, because glucose is a better substrate than lactose, so beta-galactosidase isn’t required
What are the 3 states of lac operon?
1) Repressed
2) Induced
3) Catabolite repressed
When is lac operon repressed?
When succinate is the carbon source
When is lac operon induced?
When lactose is present in the medium
