Metabolic Biochemistry Exam 1 Questions And Answers

How do allosteric effectors affect enzyme structure and function? - Answer - "from a distance" allosteric inhibitors can either activate or deactivate an enzyme. Example of allosteric inhibitor - Answer - ATP = allosteric I for ATCase. Give overview of glycogen phosphorylase covalent modification - Answer - (glycogen)n +PO4 - (glycogen)n-1 and G6P How does covalent modification affect the T and R state for glycogen phosphorylase? - Answer - Phosphorylated form favors the R-state (active) Dephosphorylated form favors the T-state (inactive) Reasons why T-state of glycogen phosphorylase is inactive - Answer - 1. Loop blocks the active site so substrate cannot bind. 2. Malformed active site: misaligned Arg for phosphate substrate binding. 3. Ser14 is not near allosteric Arg. Reasons why R-state of glycogen phosphorylase is active. - Answer - 1. Active site not blocked by loop due to flexibility. 2. Arg properly aligned to bind to phosphate. 3. Ser-phosphate goes through conformational change to be near allosteric site. What condition to metabolic pathways function under? - Answer - Steady-state: constant input of reactants. What type of Delta G does an enzyme that functions near equilibrium have? - Answer - Near-equil. = no reactant buildup so Q~Keq so Delta G ~0. Small change in [reactant] leads to change in Delta G sign and direction of reaction. What type of Delta G does an enzyme that functions far from equilibrium have? - Answer - Large neg. Delta G Too slow to maintain equil [R] and [R] and is irreversible. QKeq so Delta G 0 Changes in [R] do not alter G significantly. Define "high-energy" compounds - Answer - "packets" of energy (large neg. Delta G) are conserved by the synthesis