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Unformatted text preview: EXAM I ANSWER KEY BIOCHEMISTRY 462B - SPRING 2007 Question 1. (8 points) Describe the difference between mass action ratio Q and equilibrium constant K eq . How are they related to each other mathematically through free energy change? Q refers to the actual ratio of product and substrate concentrations in a cell while K eq refers to the ratio of product and substrate concentrations at equilibrium. ¡ G = ¢ RT ln K eq + RT ln Q Question 2. (12 points) What are the effects of the following events on the rates of glycogen synthesis and glycogen degradation? Describe the effects as increase, decrease, or no effect. G l y c o g e n G l y c o g e n Synthesis Degradation (A) Increase in intracellular Ca 2+ levels (B) Increase in circulating insulin (C) Decrease in blood glucose levels (D) Increase in circulating epinephrine (E) Increase in cAMP levels ( F ) I n c r e a s e i n A M P l e v e l s S y n t h e s i s D e g r a d a t i o n (A) Increase in intracellular Ca 2+ levels No effect Increase (B) Increase in circulating insulin Increase Decrease (C) Decrease in blood glucose levels Decrease Increase (D) Increase in circulating epinephrine Decrease Increase (E) Increase in cAMP levels Decrease Increase (F) Increase in AMP levels Decrease or no effect* Increase * AMP-activated protein kinase will decrease glycogen synthesis Question 3. (8 points) What are the regulatory enzymes (or steps) in glycolysis? What is the common trait that sets apart the reactions they catalyze from the other reactions in glycolysis? Name: ________________________ Net ID: ______________________ Section: ________ Page 2 of 4 Answer. Hexokinase, phosphofructose kinase, and pyruvate kinase. They all have large negative ¡ G' ° or ¡ G and not in equilibrium. Question 4. (8 points) Hydrolysis of ATP to ADP and inorganic phosphate has a ¡ G ´º of –30.5 kJ/mol. List and briefly describe three of the four chemical rationales for this large negative ¡ G ´º. Why is ATP kinetically stable at pH 7 despite the large decrease in free energy associated with its hydrolysis? Relief of charge repulsion Resonance stabilization of inorganic phosphate Ionization of ADP Increased hydration of ADP and inorganic phosphate relative to ATP High activation energy during its hydrolysis is the reason for the high kinetic stability of ATP, a metastable compound....
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This note was uploaded on 04/07/2009 for the course BIOC 462b taught by Professor Grimes,tsao,borque during the Spring '08 term at University of Arizona- Tucson.
- Spring '08