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CHAPTER 15 Principles of Metabolic Regulation - Coggle Diagram
CHAPTER 15 Principles of Metabolic Regulation
Synthesis
Glucose-1-Phosphate Is the Substrate
for NDP-Sugar Pyrophosphorylase
Phosphoglucomutase is reversible.
In glycogen degradation, glucose-1-phosphate is converted to glucose-6-phosphate.
In glycogen synthesis, glucose-6-phosphate is converted to glucose-1-phosphate.
Synthesis of Branches in Glycogen
UDP-Glucose Is the Substrate for Glycogen Synthase
Glycogenin Starts a New Glycogen Chain
Glycogen Is Synthesized by Glycogen Synthase
General Structure of a Glycogen Particle
Glycogen Synthesis from Glucose Occurs in Multiple Steps
Synthesis of glycogen requires more enzymes and metabolic intermediates than glycogen degradation.
Blood glucose must be:
phosphorylated
labeled with UDP
added to glycogen
Multiple steps allow for multiple points in regulation.
Integration of Glycogen Synthesis and Degradation
基本
Dealing with Branch Points in Glycogen
Glycogen phosphorylase works on nonreducing ends until it reaches four residues from an (α1->6) branch point.
Debranching enzyme transfers a block of three residues to the nonreducing end of the chain.
Debranching enzyme cleaves the single remaining (α1->6)-linked glucose, which becomes a free glucose unit (i.e., NOT glucose-1- phosphate).
Glucose-1-Phosphate Must Be Isomerized to Glucose-6-Phosphate for Metabolism
Glucose Residues Are Removed from Glycogen by Glycogen Phosphorylase
Glucose-6-Phosphate Is Dephosphorylated in the Liver for Transport Out of the Liver
Glucose Can Be Stored for Later Use as Glycogen
Glycogen is a branched polymer of α(1->4)-linked glucose with α(1->6) linkages every 12 to 14 glucose units.
Glycogen storage occurs mainly in the liver and muscle.
Glycogen is degraded to glucose units for use in energy production.
Glycogen can be made from excess blood glucose or recycling of glucogenic metabolites like lactate or certain amino acids.
Control of Glycogen Synthesis
Flow to Glycogen Synthase Is Controlled by Glucose Uptake and Phosphorylation
Glycogen Synthase Is Controlled by Phosphorylation
Glycogen synthase makes glycogen for energy storage.
Control of Carbohydrate Metabolism in the Liver
Increased hexokinase activity enables activation of glucose.
Control of Carbohydrate Metabolism in the Liver versus the Muscle
Insulin-signaling pathway
increases glucose import into muscle
stimulates the activity of muscle hexokinase
activates glycogen synthase
Control of Glycogen Breakdown
Glycogen phosphorylase cleaves glucose residues of glycogen, generating glucose-1-phosphate.
Epinephrine and Glucagon Stimulate Breakdown of Glycogen
Glucogon/epinephrine signaling pathway
starts phosphorylation cascade vis cAMP
activates glycogen phosphorylase