Compare and contrast the molecular structures and mechanisms of action of the three major hormones which control the plasma glucose concentration

Identify three major hormones as insulin, glucagon and glucorticoids / cortisol • Insulin lowers plasma [glucose] – glucagon & cortisol increase plasma [glucose] • Insulin & glucagon both peptide hormones – hydrophilic – act via different cell surface receptors and transmembrane signalling cascades to regulate activity of glycogenolytic, glycolytic and gluconeogenic plus lipolytic and lipogenic enzymes • Insulin acts via tyrosine kinase cascade to increase glycogen synthesis / decrease glycogen breakdown and inhibit hormone-sensitive lipase (HSL) / stimulate lipogenesis • Glucagon exerts rapid effects mediated via increased cAMP and activation of protein kinase A (PKA) to activate glycogen phosphorylase and HSL • Cortisol is a steroid hormone – hydrophobic – binds intracellular receptor (liganddependent transcription factor) to modulate expression of genes encoding enzymes listed above – upregulates enzymes required for lipolysis and for gluconeogenesis / reverse glycolysis • Identify key metabolic enzymes as glycogen phosphorylase, HSL, PEPCK, fructose 1,6- bisP’ase and glucose-6-P’ase • How is each metabolic enzyme regulated by insulin, glucagon and cortisol and what is the net effect on carbohydrate, fat and protein metabolism? IMPORTANT – Additional Submission Instructions  Revised Submission Deadline – 12 Noon on THURSDAY 15 DECEMBER  Word Limit 1,000 words  Please ensure that: o The essay title appears in quotation marks (to avoid being included in the Turnitin score for plagiarism) o If you include any references at the end of your essay, you precede this with the word References (spelled correctly and not in quotation marks)