Chemical reaction rate driven by affinity, by a Gibbs energy decrease
The structural change in a cancerous cell causes a corresponding change in function. Due to the decreased mitochondrial activity, glycolysis and proteolytic and lipolytic processes become the main energy sources of a cancerous cell where the extensive loss of skeletal muscle and adipose tissue occurs. The loss of adipose tissue is due to the degradation of triglycerides, while the loss of skeletal muscle is due to increased protein degradation. Tumor products such as the lipid mobilizing factor (LMF) and the proteolysis inducing factor (PIF) have catabolic effects on the host, but the synthesis of muscle protein also decreases. Lipid mobilization produces high energy but also a great loss of fat mass in cancer patients. The most important pathway of protein degradation involving the ATP-ubiquitin, also leads to the hypermetabolism characteristic of parasitism. All proteolytic and lipolytic processes, as catabolic reactions, contribute more entropy production in cancerous than in normal cells. In the following we shall study glycolysis only and compare the entropy production of glycolysis in tumorous tissue with that of the full oxidation of glucose in normal cells.
In normal cells, the full oxidation of 1 mole of glucose will release 676 kcal/mole and produces 31 moles (or 29.5 moles in the alternative pathway) of ATP. Hence, the total Gibbs free energy decrease is
(normal) = 686-7.3 × 31 × 1.7 = 301.3 kcal/mole (the sum is over reactions δ) in the respiratory chain of a normal cell (the factor 1.7, relating to the possible higher efficiency of ATP hydrolysis energy transformed into chemical energy in a living cell, is empirically introduced). Instead, in a cancerous cell glycolysis is the main process where, the total free energy release is 52 kcal/mole and 1 mole of glucose produces only 2 moles of ATP. Correspondingly, the Gibbs free energy decrease is
(cancer) = 52-7.3 × 2 = 37.4 kcal/mole in a cancerous cell. On the other hand, it was demonstrated through positron emission tomography scanning that tumor cells absorb more glucose than normal cells. Cancer cells metabolise glucose at a rate of approximately 20 times that of normal tissue . For example, while normal cells take up 2~16 g glucose from 1000 ml blood, the cancerous cells with the same tissue origin will take 70 g. Thus, the glucose consumption in cancerous cells is much higher than in healthy cells. Simultaneously, no matter whether the oxygen supply in cells is enough or not, the tumor always maintains an efficiency of glycolysis 70–80 times higher than normal. From the comparison of the ATP molecule number produced in glycolysis and glucose oxidation in the respiratory chain, we estimate the average reaction rate of the oxidation of glucose in unit volume of a cancerous cell (J
) to be at least 15~20 times higher than that in a normal cell (J
). Thus, the rates of entropy production in a cell are
The rate of entropy production in the carbon energy source reaction of a cancerous cell is estimated to be 2 or more times higher than that in a healthy cell. Furthermore, if the strong proteolytic and lipolytic processes in cancer are taken into account, the entropy production of a cancerous cell will be even higher.