NUTRITION IN SPORT

mitochondrial membrane. The flow of H+ions
(protons) through this complex constitutes a
proton-motive force that is used to drive ATP
synthesis. In terms of the energy conservation of
aerobic glucose metabolism, the overall reaction
starting with glucose as the fuel can be summa-
rized as follows:

glucose+6O 2 +38ADP+38Pifi
6CO 2 +6H 2 O+38ATP

The total ATP synthesis of 38 mol per mole of

glucose oxidized are accounted for primarily by

oxidation of reduced coenzymes in the terminal

respiratory system as follows:

ATP synthesized Source

2 Glycolysis

6 NADH by glycolysis

24 NADH

4 FADH 2

2 GTP

biochemistry of exercise 27

Oxaloacetate

Citrate

cis-aconitate

Isocitrate

α-ketoglutarate

Succinyl-CoA

Succinate

Fumarate

Malate

TCA cycle

Pyruvate

NADH + H+

NADH + H+

NAD+

NADH + H+

NAD+

NADH + H+

NAD+

NAD+

Acetyl-CoA

CoA

CoA

CO 2

CO 2

CO 2

CO 2

H 2 O

H 2 O

FADH (^2) H 2 O
FAD
Pyruvate
carboxylase
Malate
dehydrogenase
Fumarase
Succinate
dehydrogenase
Nucleotide
diphosphate
kinase
Succinyl
thiokinase
α-ketoglutarate
dehydrogenase
Isocitrate
dehydrogenase
Aconitase
Aconitase
Pyruvate
dehydrogenase
complex
Citrate
synthase
CoA
GTP
ATP ADP
GDP
CoA
Fig. 2.4Summary of reactions of the tricarboxylic acid (TCA) cycle showing sites of substrate level
phosphorylation, CO 2 production and NAD+and flavin adenine dinucleotide (FAD) reduction. The two-carbon
(2C) acetate units of acetyl-CoA are combined with 4C oxaloacetate to form 6C citrate. The latter undergoes two
successive decarboxylation reactions to yield 4C succinate which in subsequent reactions is converted into 4C
oxaloacetate, completing the TCA cycle. Enzymes are set in small type; GDP, guanosine diphosphate; GTP,
guanosine triphosphate.