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Combustion, respiration, and oxygen

 

"Experiment taught us that bodies cannot burn or animals breathe without the participation of atmospheric air; ... The most commonly held oppinion attributed to this fluid no other functions than that of cooling the blood as it passes through the lungs, and by its pressure retaining the matter of fire at the surface of combustible bodies. ... only a single kind of air, known by the names of dephlogisticated air, pure air, or vital air is fitted for combustion, respiration, and the calcination of metals; that it makes up only about a fourth part of atmospheric air, and that this portion of the air is then absorbed, altered, or converted into fixed air by the addition of a prinicple that, to avoid all discussion concerning ist nature, we shall call the base of fixed air. Thus air does not act in ist operations as a simple mechanical cause but as a priniple entering into new combinations."

 

Lavoisier Antoine-Laurent and Laplace Pierre-Simon (1783) Memoir on heat. Mémoirs de l’Académie des sciences. Translated by Guerlac H, Neale Watson Academic Publications, New York, 1982.



The famous conclusion

 

"Respiration is, therefore, a combustion, a very slow one to be precise."

Lavoisier and Laplace  (1783) Memoir on heat (translation: Gnaiger E, 1983. J. Exp. Zool. 228: 471).

 

The famous misconception

 

The heat developed in this combustion is imparted to the blood that flows through the lungs, whence it spreads throughout the animal’s body. Thus the air we breathe serves two purposes equally necessary to preserve life: it removes from the blood the base of fixed air whose excess would be very harmful; and the heat which this reaction gives to the lungs makes up for our continual loss of heat to the atmosphere and surrounding bodies.

                Animal heat is pretty much the same in the different parts of the body.

Lavoisier Antoine-Laurent and Laplace Pierre-Simon (1783) Memoir on heat. Mémoirs de l’Académie des sciences. Translated by Guerlac H, Neale Watson Academic Publications, New York, 1982.

 



Oxidation and reduction

 

"There is a general rule that oxygen does not attack organic substances dissolved in water at the temperature of the blood and at a pH of 7.

One must remember, however, as a fundamental fact, that if peroxide of hydrogen is produced in a living cell, its quantity is dependent on the requirement of that cell for oxygen. The machinery of the living cell is the dominant reigning force, not peroxide of hydrogen running riot." (p. 176).

 

"Wieland’s theory is that all oxidations are effected through the withdrawal of hydrogen from organic compounds. ... For if finely cut frog’s tissue be washed with water it no longer reduces methylene blue, but if succinic acid be added, then fumaric acid and later malic acid are abundantly produced. Dehydrogenation of succinic acid is brought about and hydrogen is „donated“ to methylene blue. ... All foods are hydrogen donators under this scheme and a t bottom hydrogen may be consdered the common fuel of all cells. ... The theory of Warburg involves the direct production of activated oxygen, through the conversion of bivalent oxide of iron into peroxide of iron, and the dissociation of the latter. Warburg denies that H2O2 ever arises biologically and affirms that activated oxygen is the cause of oxidation." (p. 176-178).

 

If one returns to the fundamental proposition that oxidation depends on the mechanism of the cell and not on the quantity of oxygen, a striking example is found in the experiments of Lund [Lund, E.J.: Am. J. Physiol., 1917-18, 45, 351, 365.] upon Paramecium caudatum. Lund found that the rate of intracellular oxidation was the same when the concentration of oxygen varied 55-fold, from 0.04 c.c. to 2.2 c.c. per 137 c.c. of liquid." (p. 185).

Lusk Graham (1928) The elements of the science of nutrition.

4th edition. Saunders Company, Philadelphia and London.



Cytochrome

 

"An important discovery of a respiratory pigment, cytochrome, common to animals, yeast, and the higher plants, was made by Keilin [Keilin, D.: Proc. Roy. Soc. (London), 1925, B, 98, 312.] Cytochrome contains a hemochromogen nucleus. The highest concentration of this pigment is found in the thoracic wing muscles of flying insects, the striated muscles of mammals and birds, and in baker’s yeast. It readily undergoes oxidation and reduction. It is too early to forecast the importance of cytochrome. However, Barbara Holmes [Holmes, B.E.: Biochem. J., 1926, 20, 812.] finds that rat carcinoma and sarcoma contain abnormally small quantities both of reduced glutathion and of cytochrome. In this she finds support of the opinion of Warburg [Warburg, O.: J. Cancer Res., 1925, 9, 148.], that cancer cells resemble anaerobic rather than aerobic organisms." (p. 185).

Lusk Graham (1928) The elements of the science of nutrition.

4th edition. Saunders Company, Philadelphia and London.



From intruder to friend

 

"When oxygen leaked into the air two aeons ago, the biosphere was like the crew of a stricken submarine, needing all hands to rebuild the systems damaged or destroyed and at the same time threatened by an increasing concentration of poisonous gases in the air. Ingenuity triumphed and the danger was overcome, not in the human way by restoring the old order but in the flexible Gaian way by adapting to change and converting a murderous intruder into a powerful friend."

 

J. E. Lovelock (1979) Gaia: A new look at life on Eath. Oxford University Press.



Low oxygen is normoxia

 

"Molecular oxygen comprises about 20 % of our atmosphere, but less than 5 % of this amount is dissolved at equilibrium in water. As a consequence of this low solubility in seawater, in freshwater and in aqueous body fluids, living cells are subjected to a universal problem of low oxygen availability."

E. Gnaiger (1983) in Polarographic Oxygen Sensors. Aquatic and

 Physiological Applications. Springer, Berlin, Heidelberg, New York.

 

"Atmospheric oxygen levels were probably 0.1% of the present when mitochondria became associated with cells early during evolution. Such low-oxygen conditions persist in extreme environments, and oxygen pressures as low as 0.3–0.4 kPa (2–3 mmHg) are observed in the intracellularmicroenvironment of mitochondria in tissues under normoxia. Even so, in typical studies with isolated mitochondria, these organelles are artificially exposed to the high partial pressure of oxygen at air saturation (c. 20 kPa), despite the fact that this condition is effectively hyperoxic, is rarely physiological, and increases oxidative stress."

Gnaiger E, Méndez G, Hand SC (2000) High phosphorylation efficiency and depression of uncoupled respiration in mitochondria under hypoxia. Proc. Natl. Acad. Sci. USA 97: 11080-11085.



Entropy

 

'Now you see that the hope and the desire of returning to the first state of chaos is like the attraction of the moth to the light, and that the man who with constant longing awaits with joy each new springtime, each new summer, each new month and new year - deeming that the things he longs for are even too late in coming - does not perceive that he is longing for his own destruction. But this desire is the very quintessence, the spirit of the elements, which finding itself imprisoned with the soul is ever longing to return from the human body to its giver. And you must know that this same longing is that quintessence inseparable from nature, and that man is the image of the world.'

Leonardo da Vinci (Cod. Arund., fol. 156 v)



Energy

 

In 1845 J. R. Mayer laid down the law of the conservation of energy, and in 1847 Helmholtz independently made the same discovery. Both contributions were rejected by the leading German scientific journal of the day. This should encourage all workers to rest assured of the ultimate recognition of work that is worth while (p. 35).

Lusk Graham (1928) The elements of the science of nutrition. 4th edition. Saunders Company, Philadelphia and London.



Steady-state

 

The cell is in fact not a single room in which all the chemical processes occur in a higgledy-piggledy manner as they occur in a beaker glass, but it is rather a well orgnaized chemical factory with different chemical processes occurring in different regions and in which substances are being elaborated as fast as they are required.

Mathews A. P. (cited by Lusk G., 1928)


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