MCB 2000 Exam 6 Questions And Answers (Verified And Updated)

MCB 2000 Exam 6 Questions And Answers (Verified And Updated) What is the chemical structure of glycogen? - answermultiple glucose monomers bound together highly branched homopolymer how is glycogen linked - answerbranches - α-1,6 linkage chain linkages - α-1,4 linkage What enzymes are involved in glycogen degradation? What reactions do they catalyze? - answer1. Glycogen phosphorylase -- phosphorolysis reaction 2. Transferase -- shifts a small oligosaccharide 3. α-1,6-glucosidase -- debranching enzyme 4. Phosphoglucomutase -- form glucose 6 phosphate α-1,6-glucosidase - answerdebranching enzyme that cleaves the α-1,6 bond --- release free glucose its a hydrolysis reaction transferase - answershifts a small oligosaccharide move 3 glucose that glycogen phosphorylase cant reach down to 2nd row glycogen phosphorylase - answerdegrades glycogen from the *non reducing end* degrades α-1,4 linkage --- yielding glucose 1 phosphate ratio of glucose 6 phosphate:glucose - answer12:1 phosphoglucomutase - answerconverts glucose-1-phosphate to glucose-6-phosphate using glucose 1,6 bisphosphate intermediate *serine 114 (Ser-114) act as a phosphoryl group carrier* what happens after glucose 6 phosphate - answerin the liver glucose 6 phosphat*ase* generates free glucose --- then released into blood *enzyme only found in the membrane of the ER, lumen side* glycogen phosphorylase regulation: allosterically - answerkey regulatory enzyme: glycogen phosphorylase have a & b form a vs. b forms of glycogen phosphorylase - answera --- active form, phosphorylated serine- 14 residue, R state is favored b --- inactive form, dephosphorylated, T state is favored What residue is phosphorylated in glycogen phosphorylase - answerserine 14 regulation of glycogen phosphorylase in liver - answerdefault state: a form in the R state (most condition active) key role: maintain adequate blood level of glucose negative regulator: glucose (R state to T state) regulation of glycogen phosphorylase in muscle - answerdefault state: b form in the T state (most condition inactive) when energy needs (inc. AMP), phosphorylase binds AMP stabilizes the R state T state is stabilized by ATP and glucose 6 phosphate glycogen phosphorylase regulation: covalent modification - answerliver: (-) glucose (R state to T state) muscles: (-) ATP & glucose 6 phosphate (+) AMP hormones signal in glycogen degradation - answerglycogen phosphorylase stimulated by G- protein signaling pathways: glucagon (liver) & epinephrine (muscle)