Glycolysis result

The first steps in glycolysis result in the conversion of a six-carbon glucose molecule to two three-carbon intermediates (Figure 6-1). 

Under anaerobic conditions, glycolysis results in a net synthesis of only two ATP molecules for each molecule of glucose metabolized (Table 6-1). 

As indicated earlier, the enthalpy balance method is a valuable tool for making an account of the pathways operating during cellular metabolism (reviewed by Kemp, 1993). In this way, it was shown by Eftimiadi and Rialdi (1982) that 36% of the heat dissipation by human neutrophils was due to the pentose phosphate pathway and the remainder (64%) to glycolysis, resulting in lactate production. The enthalpy recovery of 1.0 indicated that there was no measurable respiration, which is consistent with the almost complete absence of mitochondria from these cells. 

Fig. 8.1 Glucose metabolism in coupled neuron and astrocyte system. ATP is produced via oxidative energy metabolism (glycolysis, TCA cycle and oxidative phosphorylation) in neurons and in astrocytes. Na+ entry during electrical activity initiates increased oxidative energy metabolism within neurons. The activation of neuronal Na+-K+ ATPase in the plasma membrane leads to reduced levels of ATP, which rapidly activates glycolysis. This process requires an elevated glucose level, which is transported via the neuronal glucose transporter (GT). The generated ATP can restore the Na+/K+ balance via Na+-K+ ATPase. The rapid increase of glycolysis results in increased NADH/NAD+ and increased cytoplasmic pyruvate. In astrocytes,...

Anaerobic glycolysis results in acid production in the form of H. Glycolysis forms pyruvic acid, which is reduced to lactic acid. At an intracellular pH of 7.35, lactic acid dissociates to form the carboxylate anion, lactate, and H (the pKa for lactic acid is 3.85). Lactate and the H are both transported out of the cell into interstitial fluid by a transporter on the plasma membrane and eventually diffuse into the blood. If the amount of lactate generated exceeds the buffering capacity of the blood, the pH drops below the normal range, resulting in lac-ticacidosis (see Chapter 4). 

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