Moving Questions: A History of Membrane Transport and Bioenergetics
This book describes half a century of progress in two mainstream areas of biological research: membrane transport, initially a focus of physiologists, and oxidative phosphorylation, initially a focus of biochemists. Robinson shows how the development of new explanatory models had unexpectedly merged these inquiries into a new field, bioenergetics. In the late 1930s, explanations for the asymmetric distribution of ions between cells and their environments invoked absolute impermeabilities of the cell's surrounding membranes. But new experiments contradicted that idea and demonstrated that forming the transmembrane distributions required metabolic energy, implying the participation of active transport "pumps." Subsequent studies identified, isolated, and characterized these pumps as enzymes coupling ionic transport to the consumption of adenosine triphosphate (ATP), an "energy-rich" molecule serving as a cellular energy store. In the late 1930s oxidative phosphylation, the process of coupling ATP synthesis to oxidative metabolism, was identified. The explanatory model emerging in the next decades, however, did not follow the enzymatic precedents of known metabolic phosphorylations but rather embodied the principle that metabolic oxidations drive active transport pumps to create transmembrane distribution of ions, with these ionic asymmetries then driving ATP synthesis. It was discovered that ATP consumption can form ionic asymmetries; ionic asymmetries can drive ATP formation; and ionic asymmetries-like ATP-can also power other cellular functions.
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Accounting for Asymmetric Distributions of Na+ and
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action potential active transport amino acid amino acid sequence ATP hydrolysis ATP synthesis ATPase ATPase activity bilayer binding Biochem biochemistry Biol Biophys Boyer Ca2+ cardiotonic steroids cation cellular channels Chapter Chem chemical chemiosmotic Conway coupling cytoplasm Danielli Davson demonstrated described diffusion electrical electrochemical gradients electron energy enzyme exchange experimental experiments extracellular K+ Fenn fluxes frog frog skin giant axons glucose Glynn H+ gradients Hodgkin and Huxley Hokin Ibid impermeable incubated influx inhibited inhibitors ions K+ concentration Keynes labeling Ling lipid Maizels measured mechanism metabolic Mg2+ Mitchell Mitchell's mitochondria molecular muscle Na+ and K+ Na+ transport Na+/K+ Na+/K+-ATPase NADH nerve ouabain oxidative phosphorylation oxygen paper permeability phosphate phosphatidic acid phospholipid Physiol Physiological plasma membrane Post potassium proposed protein pump Racker radioactive ratio red blood cells reported Reprinted by permission respiratory chain serosal Skou sodium squid Steinbach stoichiometry structure studies subunits tion tissues transmembrane uncouplers Ussing vesicles