. Biological transport. Biological transport; Biological Transport. CLUES FROM ASSOCIATED EVENTS. Figure 28 Hypothetical scheme for relationship between enzyme, ATP, and magnesium ions. Such a positioning of magnesium-ATP on the membrane is proposed by Skou to permit it to displace electrons within the membrane. [From Skou, J. C. (1960), Biochim. et Biophys. Acta, 42, 19; with permission^ nance of an activated, transport-responsive state of the membrane may then be aided by the presence of high cellular levels of potas- sium ion or of amino acids, or of both. We may note that Mitchell's scheme
. Biological transport. Biological transport; Biological Transport. CLUES FROM ASSOCIATED EVENTS. Figure 28 Hypothetical scheme for relationship between enzyme, ATP, and magnesium ions. Such a positioning of magnesium-ATP on the membrane is proposed by Skou to permit it to displace electrons within the membrane. [From Skou, J. C. (1960), Biochim. et Biophys. Acta, 42, 19; with permission^ nance of an activated, transport-responsive state of the membrane may then be aided by the presence of high cellular levels of potas- sium ion or of amino acids, or of both. We may note that Mitchell's scheme included an electron- transport system possessing direction across a membrane, of the type originally proposed by Lundegaardh (1939) as the basis of anion transport. The idea that material transport is produced by this system (see the writings of Conway and of Davies), without the associated participation of a similarly anisotropic ATPase system, is not, however, being reintroduced in this hypothesis. Mitchell's proposal appears to make from the two perhaps most perplexing problems of biology—solute transport and oxidative phosphorylation —a single problem. Skou (1961) speculates that ATP acts on alkali metal trans- port by being bound to the membrane by the aromatic amino group and through the intermediation of a magnesium ion (Figure 28). A second magnesium ion may occupy a position to make one com- mon electronic system of the phosphate chain and the adenine part of the ATP, with common nonlocalized electrons (Szent-Gyorgyi, 1957; 1960). The linkage to the membrane may then conceivably 87. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Christensen, Halvor N. New York, W. A. Benjamin
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