Flashcards in Signal Transduction 3: Glucagon And Epinephrine Signalling Deck (11):
Examples of low blood sugar (hypoglycaemia)?
Coma, brain damage
Examples of high blood glucose levels (hyperglycaemia)?
How many amino acids does glucagon have?
First step of glucagon?
It binds to the receptor and activates it via a conformational change
Second step in glucagon pathway?
The receptor activates the stimulatory G protein
What are the overall steps of regulating glucose levels?
Similar to typical pathway- glucagon binds to 7TM receptor, activates G protein, then cyclic AMP, then protein kinase A, the phosphorylase kinase, then phosphorylase A (aka the phosphorylation cascade)
What does glucogen breakdown do to blood glucose?
How is glycogen breakdown rapidly turned off?
1. Hormones that stimulate glucogen breakdown are no longer present
2. The inherent GTPase activity of G-alpha subunit inactivates G protein signalling
3. Phosphodiesterase converts cAMP into AMP, which does not stimulate protein kinase A
4. A protein Phosphatase removes phosphates from phosphorylase kinase and glycogen phosphorylase, thereby inactivating the enzymes
What can also regulate the glycogen metabolism?
Hormone-triggered cAMP cascades which leads to the activation of protein kinase A and activates glycogen degradation- while at the same time, protein kinase A, along with glycogen synthase kinase, inactivates glucogen not synthase, shitting turn glycogen synthesis
Why are glycogen breakdown and synthesis reciprocally regulated?
As fuel can be stored at the same time it's used