chemistry 2100 chapter 27. metabolism metabolism is the sum of catabolism and anabolism. 2
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Chemistry 2100
Chapter 27
MetabolismMetabolism is the sum of catabolism and anabolism.
2
Metabolism
• digestion: hydrolysis
• degradation: nutrients acetyl CoA
• TCA Cycle: acetyl CoA CO2 + NADH / FADH2
• oxidative phosphorylation: NADH / FADH2 ATP
Stages of Catabolism
Catabolic Pathways
• Two principal types of compounds participating in the common catabolic pathway are:– AMP, ADP, and ATP: agents for
the storage and transfer of phosphate groups.
– NAD+/NADH and FAD/FADH2: agents for the transfer of electrons in biological oxidation-reduction reactions
N
N
N
N
NH2
OHOH
CH2
O OH
O
OH
O
OH
O
OHPOPOPO
Ad
Adenosine Triphosphate
H2O
7500 cal/mol
O P O P O P O
O
O
O
O
O
O
Ad
O P O
O
O
Ad O P O P O
O
O
O
O
+ +
H2O
7500 cal/mol
O P O P O P O
O
O
O
O
O
O
Ad
O P O
O
O
Ad O P O P O
O
O
O
O
+ +
H2O
7500 cal/mol
O P O P O P O
O
O
O
O
O
O
Ad
O P O
O
O
Ad O P O P O
O
O
O
O
+ +
H2O
31.4 kJ/mol
O P O P O P O
O
O
O
O
O
OAd
O P O
O
OAd O P O P O
O
O
O
O
+ +
+ + +R C
O
OH HO R' R C
O
O R'4 0 0 0 ca l/mo l H2 O
Coupled Reactions (and why we need them)
+ + +R C
O
OH HO R' R C
O
O R'4 0 0 0 ca l/mo l H2 O
+ + +R C
O
OH HO R' R C
O
O R'4 0 0 0 ca l/mo l H2 O
+ + +R C
O
OH HO R' R C
O
O R'16.7 kJ/mol H2 O
R C
O
OH +2500 cal/mol O P O P O P O
O
O
O
O
O
O
Ad
R C
O
O AdO
O
OP O P O P O
O
O
O
O
+
+
R C
O
OH +2500 cal/mol O P O P O P O
O
O
O
O
O
O
Ad
R C
O
O AdO
O
OP O P O P O
O
O
O
O
+
+
R C
O
OH +2500 cal/mol O P O P O P O
O
O
O
O
O
O
Ad
R C
O
O AdO
O
OP O P O P O
O
O
O
O
+
+
R C
O
OH +10.5 kJ/mol O P O P O P O
O
O
O
O
O
OAd
R C
O
O AdO
O
OP O P O P O
O
O
O
O
+
+
R C
O
O AdO
O
OP
O AdO
O
OP+
+
+ 6000 cal/mol
HO R'
R C
O
O R'
R C
O
O AdO
O
OP
O AdO
O
OP+
+
+ 6000 cal/mol
HO R'
R C
O
O R'
R C
O
O AdO
O
OP
O AdO
O
OP+
+
+ 6000 cal/mol
HO R'
R C
O
O R'
R C
O
O AdO
O
OP
O AdO
O
OP+
+
+ 25.1 kJ/mol
HO R'
R C
O
O R'
R C
O
O R'
HO R'R C
O
OH + ATP
+ AMP + PP + 14.6 kJ/mol
+
NAD+/NADH– NAD+ is a two-electron oxidizing agent, and is
reduced to NADH.– NADH is a two-electron reducing agent, and is
oxidized to NAD+. The structures shown here are the nicotinamide portions of NAD+ and NADH.
– NADH is an electron and hydrogen ion transporting molecule.
NAd
CNH2
OH
H+ 2e-
NAd
CNH2
OH H
+ +
NAD+
(oxidized form)NADH
(reduced form)
:
FAD/FADH2
– FAD is a two-electron oxidizing agent, and is reduced to FADH2.
– FADH2 is a two-electron reducing agent, and is oxidized to FAD.
– Only the flavin moiety is shown in the structures below.
AdN
N
N
NHH3C
H3C O
O
+ 2H+ + 2e-H3C
H3C O
OH
HAdN
N
N
NH
FAD FADH2
Acetyl-CoA production
Acetyl-CoA Oxidation
Electron Transfer and Oxidative Phosphorylation
Where does this all happen?
Net Effect of the Citric Acid Cycle
Acetyl-CoA + 3NAD+ + FAD + GDP + Pi + 2 H2O
2CO2 +3NADH + FADH2 + GTP + CoA + 3H+
• carbons of acetyl groups in acetyl-CoA are
oxidized to CO2
• electrons from this process reduce NAD+ and FAD
• one GTP is formed per cycle, this can be
converted to ATP
• intermediates in the cycle are not depleted
Energy Yield
Oxidative Phosphorylation
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