Biochemistry
Biochemistry
9th Edition
ISBN: 9781319114671
Author: Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.
Publisher: W. H. Freeman
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Freshly prepared mitochondria were incubated with β-hydroxybutyrate, oxidized cytochrome c, ADP, Pi, and cyanide. β-hydroxybutyrate is oxidized by an NAD+-dependent dehydrogenase.

The experimenter measured the rate of oxidation of β-hydroxybutyrate and
the rate of formation of ATP.
(a) Indicate the probable flow of electrons in this system.
(b) How many moles of ATP would you expect to be formed per mole of
β-hydroxybutyrate oxidized in this system?
(c) Why is b-hydroxybutyrate added rather than NADH?
(d) What is the function of the cyanide?
(e) Write a balanced equation for the overall reaction occurring in this
system (electron transport and ATP synthesis).

(f) Calculate the net standard free energy change (ΔG°') in this system,
using E'0 values from Table 14.1 and a ΔG°' value for ATP hydrolysis
of -32.2 kJ/mol.

CO0-
CH,
CH,
Н-С—ОН
C=0
NAD+ NADH
+H+
CH3
CH3
expand button
Transcribed Image Text:CO0- CH, CH, Н-С—ОН C=0 NAD+ NADH +H+ CH3 CH3
TABLE 14.1 Standard reduction potentials of interest in biochemistry
Oxidant
Reductant
E" (V)
Acetate + CO2 + 2H* + 2e
Pyruvate + H20
-0.70
Succinate + CO2 + 2H* + 2e
a-Ketoglutarate + H,0
-0.67
Acetate + 3H* + 2e
-0.60
Acetaldehyde + H,0
Ferredoxin (reduced)
2
Ferredoxin (oxidized) + e
1
-0.43
2H* + 2e
H2
2
-0.42
a-Ketoglutarate + CO, + 2H+ + 2e
Isocitrate
-0.38
Acetoacetate + 2H+ + 2e
B-Hydroxybutyrate
-0.35
Pyruvate + CO, + H* + 2e
Malate
-0.33
NAD+ + H* + 2e
NADH
-0.32
NADP* + H* + 2e
NADPH
2
-0.32
Lipoate (oxidized) + 2H* + 2e
Lipoate (reduced)
-0.29
1,3-Bisphosphoglycerate + 2H* + 2e
Glyceraldehyde-3-phosphate + P
-0.29
Glutathione (oxidized) + 2H* + 2e
2 Glutathione (reduced)
-0.23
FAD (free coenzyme) + 2H* + 2e
FADH2
2
-0.22
Acetaldehyde + 2H + 2e
Pyruvate + 2H + 2e
Ethanol
2
-0.20
Lactate
2
-0.19
Oxaloacetate + 2H* + 2e
Malate
-0.17
O2 + e
a-Ketoglutarate + NHị + 2H + 2e
O (superoxide)
Glutamate + H,0
1
-0.16
-0.14
FAD (enzyme-bound) + 2H* + 2e
FADH, (enzyme-bound)
-0 to -0.30
Methylene blue (oxidized) + 2H* + 2e
Methylene blue (reduced)
0.01
Fumarate + 2H* + 2e
Succinate
2
0.03
Q + 2H* + 2e
Dehydroascorbate + 2H* + 2e
Cytochrome b (+3) + e
QH2
2
0.04
Ascorbate
0.06
Cytochrome b (+2)
0.07
Cytochrome c, (+3) + e
Cytochrome c, (+2)
1
0.23
Cytochrome c (+3) + e
Cytochrome c (+2)
1
0.25
Cytochrome a (+3) + e
Cytochrome a (+2)
1
0.29
O2 + 2H+ + 2e
H2O2
0.30
Ferricyanide + 2e
Ferrocyanide
2
0.36
NO, (Nitrate) + 2H* + 2e
NO, (Nitrite) + H2O
2
0.42
Cytochrome a,(+3) + e
Cytochrome a, (+2)
0.55
Fe (+3) + e
Fe (+2)
1
0.77
0, + 2H* + 2e
H20
0.82
Note: E" is the standard reduction potential at pH 7 and 25 °C, n is the number of electrons transferred, and each potential is for the partial reaction written
as follows: Oxidant + ne
= reductant.
expand button
Transcribed Image Text:TABLE 14.1 Standard reduction potentials of interest in biochemistry Oxidant Reductant E" (V) Acetate + CO2 + 2H* + 2e Pyruvate + H20 -0.70 Succinate + CO2 + 2H* + 2e a-Ketoglutarate + H,0 -0.67 Acetate + 3H* + 2e -0.60 Acetaldehyde + H,0 Ferredoxin (reduced) 2 Ferredoxin (oxidized) + e 1 -0.43 2H* + 2e H2 2 -0.42 a-Ketoglutarate + CO, + 2H+ + 2e Isocitrate -0.38 Acetoacetate + 2H+ + 2e B-Hydroxybutyrate -0.35 Pyruvate + CO, + H* + 2e Malate -0.33 NAD+ + H* + 2e NADH -0.32 NADP* + H* + 2e NADPH 2 -0.32 Lipoate (oxidized) + 2H* + 2e Lipoate (reduced) -0.29 1,3-Bisphosphoglycerate + 2H* + 2e Glyceraldehyde-3-phosphate + P -0.29 Glutathione (oxidized) + 2H* + 2e 2 Glutathione (reduced) -0.23 FAD (free coenzyme) + 2H* + 2e FADH2 2 -0.22 Acetaldehyde + 2H + 2e Pyruvate + 2H + 2e Ethanol 2 -0.20 Lactate 2 -0.19 Oxaloacetate + 2H* + 2e Malate -0.17 O2 + e a-Ketoglutarate + NHị + 2H + 2e O (superoxide) Glutamate + H,0 1 -0.16 -0.14 FAD (enzyme-bound) + 2H* + 2e FADH, (enzyme-bound) -0 to -0.30 Methylene blue (oxidized) + 2H* + 2e Methylene blue (reduced) 0.01 Fumarate + 2H* + 2e Succinate 2 0.03 Q + 2H* + 2e Dehydroascorbate + 2H* + 2e Cytochrome b (+3) + e QH2 2 0.04 Ascorbate 0.06 Cytochrome b (+2) 0.07 Cytochrome c, (+3) + e Cytochrome c, (+2) 1 0.23 Cytochrome c (+3) + e Cytochrome c (+2) 1 0.25 Cytochrome a (+3) + e Cytochrome a (+2) 1 0.29 O2 + 2H+ + 2e H2O2 0.30 Ferricyanide + 2e Ferrocyanide 2 0.36 NO, (Nitrate) + 2H* + 2e NO, (Nitrite) + H2O 2 0.42 Cytochrome a,(+3) + e Cytochrome a, (+2) 0.55 Fe (+3) + e Fe (+2) 1 0.77 0, + 2H* + 2e H20 0.82 Note: E" is the standard reduction potential at pH 7 and 25 °C, n is the number of electrons transferred, and each potential is for the partial reaction written as follows: Oxidant + ne = reductant.
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