CHAPTER 6 REDOX REACTIONS AND BIOENERGETICS 119
CH 2
HH
H
OH OH
H
O
O O
C
NH 2
O PR
H
O
N
CH 2
HH
H
OH OH
In NADP this hydroxyl group
is esterified with phosphate
H
O
O O
O P O
C
NH 2
2e
2H
O
HH HH
N
N
NH 2
N N
N
:
R
C
NH 2 H
O
N
:
Figure 6.3The oxidation of NAD+to NADH is a two-electron process with the release of only one proton.
1.0
0.5
0.0
Fraction reduced
Midpoint potential, Em
Potential (mV)
Absorbance
Wavelength, λ (nm)
Fully
reduced
Partly
reduced
Fraction
reduced
Fully
oxidized
Isobastic
point
Platinum
electrode
Reference
electrode
Light Absorbance
log
Titration
cuvette
Syringe
containing
chemical
titrant to
adjust
potential
Voltmeter
Measured
potential
Figure 6.4The determination of midpoint potentials using redox titrations.