Download TCA CYCLE

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TCA CYCLE
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to fat
to fat
AcCoA
pyruvate
citrate
synthase
citrate
aconitase
to glucose
oxaloacetate
isocitrate
NADH
isocitrate
dehydrogenase
malate
dehydrogenase
NADH
malate
α-ketoglutarate
CoA
fumarase
α-KG dehydrogenase
fumarate
succinate
dehydrogenase
FADH2
succinyl
CoA
succinate
NADH
succinate
thiokinase
GTP
Figure 12-1
The Tricarboxylic Acid (TCA) Cycle
153
BG McGraw-Hill: Gilbert, Basic Concepts in Biochemistry, JN 5036
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Basic Concepts in Biochemistry
TCA CYCLE1 (see Fig. 12-1.)
Function:
To burn the acetyl-CoA made from fat, glucose, or
protein in order to make ATP in cooperation
with oxidative phosphorylation.
Location:
All cells with mitochondria.
Connections: From glycolysis through acetyl-CoA.
Pyruvate makes oxaloacetate and malate through
the anaplerotic reactions.
To b oxidation through acetyl-CoA.
To amino acid degradation through acetyl-CoA
and various intermediates of the cycle.
Regulation:
Supply and demand of TCA cycle.
Availability of NAD and FAD as substrates.
Inhibition by NADH.
High-energy signals turn off.
Low-energy signals turn on.
ATP yield:
Pyruvate ¡ 15ATP
Acetyl-CoA ¡ 12ATP
Equations:
Pyruvate GDP Pi 3NAD FAD ¡
3CO2 GTP 3NADH FADH2 3H
Acetyl-CoA GDP Pi 2NAD FAD ¡
2CO2 GTP 2NADH FADH2 2H
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The tricarboxylic acid cycle is also known as the Krebs cycle or the citric acid cycle. Why
give something so central to life only one name?
BG McGraw-Hill: Gilbert, Basic Concepts in Biochemistry, JN 5036