Thermodynamics review and Intro to Metabolism Practice Problems

Thermodynamics review and Intro to Metabolism Practice Problems

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BICH 411 Thermodynamics review and Intro to Metabolism Practice Problems Compiled by Dr. L Mullins January 2006 Biochemistry 411 Introduction to Metabolism Practice Problems These are problems that have been given as homework, quiz and exam questions. All answers should be correct, but there is always a possibility that I miss- typed an answer. So work out to verify!! 1. Fructose-1,6-diphosphate + H 2 0 Fructose-6-phosphate + Pi Fructose G o ’ = -15.9 kj/mol Diphosphatase Fructose-6-phosphate Glucose-6-phosphate Phosphohexoisomerase K’ eq = 2.0 Glucose-6-phosphate Glucose-1-phosphate Phosphoglucomutase K’ eq = 0.0526 Fructose-1,6-diphosphate + H 2 0 Glucose-1-phosphate + Pi From the above information, calculate the K’ eq and G o ’ for the overall reaction shown below the line. Two ways proceed. Quickest way, K’ 1eq = e -( Go’/RT) = e -[(-15,900 J/mol)/(8.3145J/mol o K X 298 o K)] = 612 K’ eqnet = K’ 1eq X K’ 2eq X K’ 3eq = 612 X 2.0 X 0.0526 = 64.40 G o net = -RTLn K’ eqnet G o net = -(8.3145 J/mol o K X 298 o K)Ln(64.41)= -10,320 J/M = -10.3 kJ/mol Slightly longer way, G o 2 = -RTLn(K’ 2eq ) = - (8.3145 J/Mol o K X 298 o K)Ln(2) = -1,717.4 J/mol G o 3 = -RTLn(K’3 eq ) = - (8.3145 J/Mol o K X 298 o K)Ln(0.0526) = +7,297.0 J/mol G o net = G o 1 + G o 2 + G o 3 = -15,900 kJ/mol + -1,717.4 J/mol + 7,297 J/mol = -10,320 J/mol = -10.3 kJ/mol K’ eqnet =e - Go’net /RT = e -[(-10,320 J/mol)/(8.3145J/mol o K X 298 o K)] = 64.40 2. Phosphofructokinase catalyzes the conversion of ATP and fructose- 6- phosphate ( F6P) to fructose- 1,6- phosphate (FBP) and ADP. The reaction is insensitive to changes in the concentrations of F6P and FBP. What can you determine about the reaction? PFK operates far from equilibrium so it is not sensitive to changes in concentrations. PFK catalyzes a rate- determining step of glycolysis. 3. Phosphoglucose isomerase catalyzes the conversion of glucose-6-phosphate to fructose-6-phosphate.
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Thermodynamics review and Intro to Metabolism Practice Problems

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