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BCCB2000 Lecture 14 Questions Exam Study Guide
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BCCB2000 Lecture 14 QuestionsExam Study Guide
The free energy for ATP hydrolysis in vivo is actually greater than the standard free
energy change of -30 kJ mol-1 because:
A. of the actual concentrations of ATP and its hydrolysis products in cells.
B. it can participate in phosphoryl group transfers.
C. All of the above
D. it has stronger electrostatic repulsion.
E. it can easily be formed from other nucleotide triphosphates. - Answer A. of the actual
concentrations of ATP and its hydrolysis products in cells.
Which of the following half-reactions has the greatest reduction potential (i.e. can act as
the better reducing agent) compared with all the others in the list.
A. O2 + 2H+ + 2e- ——> H2O2 E'o = 0.295V
B. NAD+ + H+ + 2e- ——> NADH E'o = -0.320V
C. NO3- + 2H+ + 2e- ---> NO2- + H2O E'o = 0.421V
D. Fumarate2- + 2H+ +2e- ——> succinate2- E'o = 0.031V - Answer B. NAD+ + H+ + 2e-
——> NADH E'o = -0.320V
The chemical name for ATP is alanine triphosphate.
True or False? - Answer False
Calculate (with 2 significant figures) the standard Gibbs Free Energy available for the
reaction:
Pyruvate + NADH + H+ ——> lactate + NAD+
Given the following information:
Pyruvate + 2H+ + 2e- ——> lactate E'o = -0.19V
NAD+ + H+ + 2e- ——> NADH E'o = -0.32V
Faradays constant (F) = 96485 J V-1 mol-1
A. -98 kJ/mol
, B. -98,000 kJ/mol
C. -25 kJ/mol
D. +25 kJ/mol
E. -25,000 kJ/mol
F. +98 kJ/mol - Answer C. -25 kJ/mol
The reaction:
NAD+ + H+ + 2e- ——> NADH E'o = -0.32V
occurs in the reverse direction in the overall reaction and so we must reverse the sign of
the reduction potential: + 0.32V
ΔE'o = -0.19 + 0.32 = 0.13V
ΔG'o = -nFΔE'o
Two electrons are transfered so n=2
F = Faradays constant = 96485 J V-1 mol-1
ΔG'o = -2 x 96485 x 0.13 = -250861 J/mol = -25 kJ/mol (2 sig fig)
If the standard Gibbs Free Energy for the hydrolysis of ATP is -30.5kJ/mol, then it would
take +30 kJ/mol to synthesise ATP from the concentrations of ADP and Pi that exist in
the cell.
True or False? - Answer False
Which of the following half-reactions has the greatest oxidising potential (i.e. can act as
the better oxidising agent) compared with all the others in the list.
A. Fumarate2- + 2H+ +2e- ——> succinate2- E'o = 0.031V
B. NO3- + 2H+ + 2e- ---> NO2- + H2O E'o = 0.421V
C. O2 + 2H+ + 2e- ——> H2O2 E'o = 0.295V
D. NAD+ + H+ + 2e- ——> NADH E'o = -0.320V - Answer B. NO3- + 2H+ + 2e- ---> NO2- +
H2O E'o = 0.421V
The Standard Free energy change for ATP hydrolysis is large and negative
ΔG'o = -30.5 kJ/mol
However the actual free energy of hydrolysis (ΔG) of ATP in cells may be smaller or
larger because it depends upon the cellular concentrations of ATP, ADP, and Pi.
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