ps7.htm

CHE 472 Problem Set #2- Phosphorylation and Redox Reactions

1) Using the values for the standard free energies given in the attached table, determine whether each of the following reactions will proceed spontaneously in the direction written, under standard conditions:

b) ATP + glycerol ---> Glycerol 3-phosphate + ADP

c) ATP + pyruvate ---> phosphoenolpyruvate + ADP

d) ATP + glucose ---> glucose 6-phosphate + ADP

2) The standard free energy change for the reaction: Arginine + ATP ---> Phoshoarginine + P_i

is +0.4 kcal mol-1. From this information and that in Table 11.3, calculate te change in standard free energy for the reaction:

₂

3) The following half reactions play important roles in metabolism:

₂

⁺

₂

NADH + H⁺ ---> NAD⁺ + 2H⁺ + 2e^-

b) Which one is the reduction?

c) Write the equation for the overall reaction.

d) Which reagent is the oxidizing agent?

e) Which is the reducing agent?

f) Which reagent gets reduced?

g) Which gets oxidized?

4) Using the standard reduction potentials given in the attached table, predict which molecule will be the reducing agent in a coupled oxidation-reduction reaction involving each of the following pairs of compounds. Assume standard conditions.

⁺

b) Pyruvate/lactate and ubiquinone/ubiquinol (Q/QH₂)

c) Cytochrome f and cytochrome b₅

d) Fumarate/succinate and ubiquinone/ubiquinol.

5) Using the data in the attached table, calculate the standard reduction potential and standard free energy change for each of the following oxidation-reduction reactions.

⁺

b) Succinate + 1/2 O₂ ---> Fumarate + H₂O

c) Ubiquinol (QH₂) + 2 cyt³⁺ ---> Ubiquinone + 2 cyt c²⁺+ 2H⁺

6) The standard reduction potential for ubiquinone (Q) is +0.04V, and the standard reduction potential for flavin adenine nucleotide (FAD) is -0.22V. Show that the oxidation of FADH₂ by Q theoretically liberates enough energy to drive the synthesis of ATP from ADP and P_iunder standard conditions.

Standard Free Energies of Hydrolysis for selected compounds:

Compound DGo' (kcal/mol) DGo' (kJ/mol)

Phosphoenolpyruvate -14.8 -62

Carbamoyl Phosphate -12.3 -52

1,3 Bis phosphoglycerate -11.7 -49

Creatine Phosphate -10.3 -43

Pyrophosphate (PP_i) -8.0 -33

ATP (to ADP) -7.3 -30

Glucose 1-phosphate -5.0 -21

Glucose 3-phosphate -3.3 -14

Glycerol 3-phosphate -2.2 -9

Standard Reduction Potentials for Some Biologically Important Reactions:

Reduction Half Reaction E^o'(V)

Acetyl CoA + CO2 + H⁺ + 2e^---> Pyruvate + CoA -0.48

2H⁺ + 2e^---> H₂ -0.42

a-Ketoglutarate + CO₂ + 2H⁺ + 2e^---> Isocitrate -0.38

NAD+ +2H⁺ + 2e^- --> NADH + H⁺ -0.32

FAD + 2H⁺ + 2e^---> FADH₂ -0.22

FMN + 2H⁺ + 2e^- --> FMNH₂ -0.22

Acetaldehyde + 2H⁺ + 2e^---> Ethanol -0.20

Pyruvate + 2H⁺ + 2e^---> Lactate -0.18

Oxaloacetate + 2H⁺ + 2e^---> Malate -0.17

Cyt b₅, Fe³⁺ + e^---> Fe²⁺ 0.02

Fumarate + 2H⁺ + 2e^---> Succinate 0.03

Ubiquinone (Q) + 2H⁺ + 2e^---> Ubiquinol (QH2) 0.04

Cyt c,Fe³⁺ + e^---> Fe²⁺ 0.23

Cyt f,Fe³⁺ + e^---> Fe²⁺ 0.36

1/2 O₂ + 2H⁺ + 2e^---> H₂O 0.82

Solutions to Problem Set 6:

Problem #1
Problem #2
Problem #3
Problem #4
Problem #5
Problem #6

Return to CHE 472 Syllabus

Compound	DGo' (kcal/mol)	DGo' (kJ/mol)
Phosphoenolpyruvate	-14.8	-62
Carbamoyl Phosphate	-12.3	-52
1,3 Bis phosphoglycerate	-11.7	-49
Creatine Phosphate	-10.3	-43
Pyrophosphate (PP_i)	-8.0	-33
ATP (to ADP)	-7.3	-30
Glucose 1-phosphate	-5.0	-21
Glucose 3-phosphate	-3.3	-14
Glycerol 3-phosphate	-2.2	-9

Reduction Half Reaction	E^o'(V)
Acetyl CoA + CO2 + H⁺ + 2e^---> Pyruvate + CoA	-0.48
2H⁺ + 2e^---> H₂	-0.42
a-Ketoglutarate + CO₂ + 2H⁺ + 2e^---> Isocitrate	-0.38
NAD+ +2H⁺ + 2e^- --> NADH + H⁺	-0.32
FAD + 2H⁺ + 2e^---> FADH₂	-0.22
FMN + 2H⁺ + 2e^- --> FMNH₂	-0.22
Acetaldehyde + 2H⁺ + 2e^---> Ethanol	-0.20
Pyruvate + 2H⁺ + 2e^---> Lactate	-0.18
Oxaloacetate + 2H⁺ + 2e^---> Malate	-0.17
Cyt b₅, Fe³⁺ + e^---> Fe²⁺	0.02
Fumarate + 2H⁺ + 2e^---> Succinate	0.03
Ubiquinone (Q) + 2H⁺ + 2e^---> Ubiquinol (QH2)	0.04
Cyt c,Fe³⁺ + e^---> Fe²⁺	0.23
Cyt f,Fe³⁺ + e^---> Fe²⁺	0.36
1/2 O₂ + 2H⁺ + 2e^---> H₂O	0.82