Glucose Catabolism
Cellular Respiration : the oxidation of glucose to produce ATP and involves 4 sets of reactions:
1. Glycolysis : a set of reactions in which 1 glucose molecule is oxidized and 2 pyruvic acid molecules are produced. This reaction also produces 4molecules of ATP (but uses 2 ATP in the reaction) and 2 energy containing NADH + H+. This process occurs in the cytosol.
1 Glucose + 2 ATP 2 Pyruvic Acid + 4 ATP + 2 NADH + H+
The Fate of Pyruvic Acid
This depends upon the availability of oxygen. If oxygen is low (anaerobic conditions) such as in skeletal muscles during strenuous exercise, pyruvic acid is reduced by the addition of two hydrogen atoms to form Lactic Acid (Lactate).
2 Pyruvic Acid + 2 NADH + 2 H+ → 2 Lactic Acid + 2 NAD+
(Oxidized)
(Reduced)
Lactic acid diffuses out of skeletal muscle and enters the blood. Hepatocytes remove lactic acid from the blood and convert it back to pyruvic acid. The buildup of lactic acid contributes to muscle fatigue. In the presence of plentiful oxygen (aerobic conditions), most cells convert pyruvic acid to acetyl coenzyme A (CoA). This is the link b/t glycolysis and the Krebs Cycle.
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