This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
[{'content': 'Which of the following is TRUE about the liver enzymes which are responsible for dephosphorylation and phosphorylation? \nSelect and explain. \nA. Phosphorylase is always activated by cAMP dependent Protein kinase, B. Always activates the enzyme, C. Catecholamines does not have any role in this process, D. Phosphorylation of glycogen synthase increases its activity', 'role': 'user'}, {'content': "Answer: A \nExplanation: At the same time as phosphorylase is activated by a rise in concentration of cAMP ( phosphorylase kinase), glycogen synthase is conveed to the inactive form; both effects are mediated cAMP-dependent protein kinase. Phosphorylation is increased in response to cAMP formed from ATP by adenylyl cyclase in response to hormones such as epinephrine, norepinephrine, and glucagon. Phosphorylation of glycogen phosphorylase increases its activity; phosphorylation of glycogen synthase reduces its activity. Ref: Bender D.A., Mayes P.A. (2011). Chapter 19. Metabolism of Glycogen. In D.A. Bender, K.M. Botham, P.A. Weil, P.J. Kennelly, R.K. Murray, V.W. Rodwell (Eds), Harper's Illustrated Biochemistry, 29e.", 'role': 'assistant'}]