BioPHYSICAL chemistry

5.18 Tyrosine can accept one proton on its nitrogen atom and can donate

two protons, one from the carboxyl group and the other from the

hydroxyl group. With increasing pH tyrosine changes from H 3 Tyr+,

to H 2 Tyr, to HTyr−, and then to Tyr^2 −.

5.19 The reduced tyrosine in very energetically unfavorable compared to

the neutral tyrosyl.

5.20Protons can travel long distances by following proton pathways invol-

ving hydrogen-bonding networks.

5.21 Recent data suggest that protons can travel through tunneling

mechanisms that are normally thought to be restricted to electrons.

CHAPTER 6

6.1 Oxidation occurs at the positive electrode, the anode.

6.2 The overall reaction is the sum of the two half reactions:

Zn (solid) ↔Zn^2 ++2e− Em=+0.76 V

Cu^2 ++2e−↔Cu (solid) Em=+0.34 V

Zn (solid) +Cu^2 +↔Cu (solid) +Zn^2 + Em=+1.1 V

6.3 The higher the midpoint potential, the better an oxidant the protein is.

6.4 The energy to make one ATP is 2.1 × 10 −^19 J. A single 700-nm photon

has enough energy.

6.5 At the midpoint potential, the concentrations of the oxidized and

reduced species are equal.

6.6

=−(5.9 −10) =+4.1

6.7 (a)

(b)

(c) EE

RT

nF

A

A

oxidized

reduced

ln

[]

[]

=−^0 =125 mVV

mV

mV

.

ln

+=ln(. ).

59 6

10

01 654

EE

RT

nF

A

A

oxidized

reduced

ln

[]

[]

=−^0 =125 mVV

mV

mV

.

ln

+=ln( )

59 6

10

1 125

EE

RT

nF

A

A

oxidized

reduced

ln

[]

[]

=−^0 =125 mVV

mV

mV

.

ln

+=ln( ).

59 2

10

10 184 2

→=log. =

[ATP]

[ADP]

or

[ATP]

[ADP]

2 1 126

log log.

[ATP]

ADP

[ATP]

[ADP]

=+= 20 + 41.

=− −

()−

.(. )( )

8000

2320 298

cal mol^1

cal/(Kmol) K

425 (.)

log

[]

.

ATP

[ADP][P ]

°

RT

pH

i

=− −

Δ

Δ

G

n

23

448 ANSWERS TO PROBLEMS

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