Biochemistry
Biochemistry
6th Edition
ISBN: 9781305577206
Author: Reginald H. Garrett, Charles M. Grisham
Publisher: Cengage Learning
Question
Chapter 19, Problem 16P
Interpretation Introduction

Interpretation:

The number of molecules of oxaloacetate in the mitochondrion and definition of pOAA should be determined.

Concept Introduction:

The expression used to determine the standard free energy is:

  ΔG=ΔG0'+RTln[Oxaloacetate][NADH][Malate][NAD+]

Here ΔG is the observed free energy change in J, ΔG0' is the standard free energy change in J, R is the gas constant, T is the temperature in K and [Malate] is the concentration of Malate in M.

Expert Solution & Answer
Check Mark

Explanation of Solution

The enzyme which converts malate into oxaloacetate is malate dehydrogenase. The reaction is as shown:

  Malate + NAD+  Oxaloacetate + NADH + H+

ΔG0 = 29.7 kJ/mol

Below reaction is used to determine the standard free energy:

  ΔG=ΔG0'+RTln[Oxaloacetate][NADH][Malate][NAD+]

Here ΔG is the observed free energy change in J, ΔG0' is the standard free energy change in J, R is the gas constant, T is the temperature in K and [Malate] is the concentration of Malate in M.

At equilibrium ΔG =0 at equilibrium. Thus, the equation will be:

  ΔG=RTln[Oxaloacetate][NADH][Malate][NAD+]

After rearranging the equation, we will get:

  [Oxaloacetate][NADH][Malate][ NAD +]=e Δ G 0' RT[Oxaloacetate]=[Malate][NADH][ NAD +]e Δ G 0' RT

Plugging in the values to determine the oxaloacetate concentration:

  [Oxaloacetate]=(0.22× 10 3)(20)e 29.700 8.314×( 273+25 )                        = 2.14×108 M

Concentration of oxaloacetate is 0.214 µM.

Below formula will be used to determine the volume:

  V=π(d2)2l

Here, V = Volume, d =diameter, l = length

Plugging the values in the above equation to determine the volume:

  V=3.14( 1× 10 6 m2)(2× 10 6m)  =1.57×1018m3×1000000 cm3m3×1 L1000  cm3  =1.57×1015 L

Now we have to calculate concentration and volume now determine the oxaloacetate molecules:

  N=(2.14× 10 8 molL)(1.57× 10 15L)(6.02× 10 23 molecules mol)   =20.2 molecules    = 20 molecules

There are 20 molecules of oxaloacetate in the mitochondrion.

The pOAA can be determined from the negative log of oxaloacetate concentration:

  pOAA =log[oxaloacetate]           =log(2.14× 10 8M)          =(7.67)          =7.67

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