Question

Explain how in a post-absorptive (fasting) state, glucagon indirectly contributes to hepatic gluconeogenesis via CREB and the bi-functional enzyme and simultaneously suppresses glycolysis.

Answer 1

During fasting, blood glucose goes below than 5mM and certain organ required only glucose for their function like brain so new glucose need to be synthesized.

Glucogon hormone or signal molecule increases during this stress condition and bind to GPCR receptor and activates GPCR pathways in which 1st G alpha protein get activated and then it activates adenyl cyclase which leads to synthesis of cAMP and cAMP activated cAMP response Element Binding protein (CREB) that acts as transcrition factor and synthsized gluconeogenesis enzyme which start reversal of glycolysis and shut down glycolysis.

Gluconeogenesis act as conversion Oxaloacetate( of TCA cycle ) to for Phosphoenol pyruvate which leads to glucose synthesis.

Hope it's clear..thanks