Problem A) The standard reduction potentials for the following reactions are giv

ID: 494784 • Letter: P

Question

Problem A)

The standard reduction potentials for the following reactions are given below.

Pyruvate + 2H+ + 2e- Lactate E = -0.190 V

NAD+ + 2H+ + 2e- NADH/H+ E = -0.320V.

Calculate G for the overall spontaneous reaction making use of the relationship between E and G.

Problem B)

Calculate the G for the reaction given the equilibrium constant is 1.97 and the physiological relevant temperature is 37 C.

fructose-6-phosphate glucose-6-phosphate

Problem C)

Calculate the ratio of [A- ]/[HA] of a 0.1 M phosphate buffer (pKa = 6.86) at pH 7.2..

Add 1st reaction with 2nd reverse reaction ===>

Gives

Pyruvate + NADH ------> lactate + NAD+

Erxn = 0.32 - 0.19 = 0.13 V

delta G = -nFE

n = no of lelectrons = 2 [since 2 electrons are involved ]

F = 96500 C

E = 0.13 V

delta G = -25.090 KJ

DG0’ = - RT ln Keq - equation

Given, Keq = 1.97 , T = 370C = 310.15 K

R= universal gas constant = 0.00831 kJmol-1K-1

Putting the values in equation 1

DG0’ = - (0.00831 kJmol-1K-1) (310.15 K) ln (1.97)

= - (2.577 kJmol-1) ln (1.97) = -(2.577 kJmol-1) (0.678) = - 1.75 kJmol-1

Hence, DG0’ = - 1.75 kJmol-1

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