Biology Reference
In-Depth Information
H
2
(a)
Succinic acid
C
4
H
6
O
4
H
2
Acetic acid
C
2
H
4
O
2
Acetic acid
C
2
H
4
O
2
Fumaric acid
C
4
H
4
O
4
H
2
O
CO
Malic acid
C
4
H
6
O
5
Pyruvic acid
C
3
H
4
O
3
Oxaloacetic acid
C
4
H
4
O
5
CO
2
H
2
(b)
HS
CoA
CO
2
Pyruvate
Acetyl-CoA (C2)
NAD
+
NADH + H
+
Citric acid (C6)
H
2
O
HS
CoA
H
2
O
Cis-Aconitic acid (C6)
Oxaloacetic acid (C4)
H
2
O
NADH + H
+
Isocitric acid (C6)
NAD
+
Malic acid (C4)
NAD
+
H
2
O
NADH + H
+
Fumaric acid (C4)
Oxalosuccinic
acid (C6)
ATP
FADH + H
+
ADP
FAD
+
CO
2
GTP
NAD
+
GDP
Alpha-ketoglutaric
acid (C5)
Succinic acid (C4)
NADH + H
+
CO
2
H
2
O
Succinyl CoA (C4)
HS
CoA
HS
CoA
Figure 3
Two versions of he TCA cycle.
(a) Cycle proposed by Thunberg in 1920 to link various three carbon sugars that figure in oxidative
metabolism. (b) the citric acid cycle as understood today.
