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Summary of Chapter 13
1. Metabolic inhibitors, genetic defects and isotope labeled compound are useful tool to study
metabolism systems, such as glycolysis, phenylalanine metabolism and the metabolic origin of the
nitrogen atom in heme.
2. Radioactive isotope decay is a first order kinetic, i.e., v = k[A]. Therefore, the half-life of
radioactive isotope is t1/ 2 =
ln 2 0.693
.
=
k
k
3. Most metabolisms are carried out in specific organelles. For example, glycolysis takes place in
cytosol, whereas the citric acid cycle and the oxidative phosphorylation processes occur in
mitochondria. Important metabolic functions are listed in Table 15-2.
4. ATP is the most important cellular energy currency because
1. ATP hydrolysis produces ∆G°’ = -30.5 kJ/mol which can be used as an input energy of
endergonic reaction. Therefore, numerous endergonic biological processes are coupled with ATP
hydrolysis.
glucose + Pi → glucose-6-phosphate ---------------------------------- -- endergonic (∆G’ = +13.8 > 0)
ATP + H2O → ADP + Pi -----------------------------------------------------exergonic (∆G’ = -30.5 < 0)
Coupled reaction: glucose + ATP → glucose-6-phosphate + ADP ---- exergonic (∆G’= -16.7 <
0)
2. ATP occupied the middle rank of phosphoryl-transfer energy production. Therefore, ADP can
accept Pi from high-energy phosphate donor compounds, such as PEP, and also ATP can donate
Pi to low-energy phosphate acceptor compound, such as glucose.
5. Exergonic ATP hydrolysis is due to:
1. Poor resonance stabilization of phosphoanhydride bonds, P-O-P.
2. High electrostatic repulsion between O-⋅⋅⋅⋅⋅⋅O3. Small solvation energy since there is no hydrogen bond donor.
6. Four major roles of ATP are:
1. Early stage of nutrient breakdown, such as production of glucose-6-phosphate.
2. Production of other nucleotide phosphates, such as GTP and UTP
3. Physiological processes, such as muscle contraction and transportation of ions against
concentration gradient.
4. Higher energy production for some special processes by ATP → AMP + PPi → AMP + 2Pi
7. ATP formation processes are:
1. Substrate-level phosphorylation, PEP + ADP → Pyruvate + ATP
2. Oxidative phosphorylation and photophosphorylation
3. Adenylate kinase reaction, AMP + ATP → 2ADP which are turned to ATP by either 1 or 2 process.
8. Excess of ATP are stored as phosphocreatine, ATP + creatine → phosphocreatine + ADP.
9. ATP turnover is relatively fast in biological system.
10. ∆G is additive, ∆G = Σ∆Gi
11. Electrons are transferred in oxidation-reduction reactions, such as Fe3+ + Cu+ → Fe2+ + Cu2+
12. Oxidation-reduction reactions can be presented by half-reactions or redox couples,
Fe3+ + e- → Fe2+
and Cu+ → Cu2+ + e [ A ] Boxn+ 

13. Free energy change of Aoxn+ + Bred → Ared + Boxn+ reaction is: ∆G = ∆G o + RT ln red
 A n+ [ B ]
 ox
red 
[ ]
[ ]
Also, ∆G = ∆G° + RTlnK and K = e − ( ∆G °− ∆G )/ RT
At equilibrium, ∆G = 0, ∆G° = -RT lnKeq
and
K eq = e − ∆G° / RT
14. Free energy change, ∆G, can be determined by simply measuring its redox potential, ∆E, with volt
meter, ∆G = -nF∆E. Note positive ∆G gives negative ∆E.
∆E of
Aoxn+ + Bred → Ared + Boxn+
reaction is:
n+


[ Ared ] Box  where n and F are number of electron and Faraday constant.
RT
∆E = ∆E o −
ln n +
nF  Aox [ Bred ] 
[ ]
[ ]
15. Free energy change in a concentration gradient, such as (Ain + Bin → Aout + Bout) is:
 [ Aout ][ Bout ] 
 ∆G° = 0 since the chemical compositions of the inside and outside are
∆G = RT ln
 [ Ain ][ Bin ] 
the same.
16. Free energy change in a concentration gradient with membrane potential of ionic substances is:
Flow direction: A(in) → A(out)
 [ Aout ] 
where ∆Ψ = Ψ(out) - Ψ(in).
 + Z A F∆Ψ
∆G = RT ln
 [ Ain ] 
where ZA = ionic charge of A (+1 for Na+, +2 for Ca2+), F = Faraday constant, ∆Ψ = charge
difference across the membrane, i.e., ∆Ψ = Ψ(out) - Ψ(in).
Note: Flow direction: A(out) → A(in)
 [ Ain ] 
where ∆Ψ = Ψ(in) - Ψ(out).
 + Z A F∆Ψ
∆G = RT ln
 [ Aout ] 