key concept

9.2

In the Presence of Oxygen, Glucose Is Fully Oxidized

The aerobic pathways of glucose catabolism oxidize glucose completely to CO2 and H2O. Initially, the glycolysis reactions convert the six-carbon glucose molecule to two three-carbon pyruvate molecules (Figure 9.5). Pyruvate is then converted to CO2 in a second series of reactions beginning with pyruvate oxidation and followed by the citric acid cycle. In addition to generating CO2, the oxidation events are coupled with the reduction of electron carriers, mostly NAD+.

image
Figure 9.5 Glycolysis Converts Glucose into Pyruvate Glucose is converted to pyruvate in ten enzyme-catalyzed steps. Along the way, two ATP are used (Steps 1 and 3), two NAD+ are reduced to two NADH (Step 6), and four ATP are produced (Steps 7 and 10).
Page 177

focus your learning

  • Glucose is partially oxidized to pyruvate during glycolysis.

  • The generation of acetyl coenzyme A by pyruvate oxidation enables the entry of carbon from glucose into the citric acid cycle for further oxidation.

  • A large amount of energy is captured in electron carriers and in GTP as acetyl CoA is fully oxidized during the citric acid cycle.

We will begin our consideration of the catabolism of glucose with a closer look at glycolysis.