Showing papers on "Electrochemical gradient published in 1969"
TL;DR: A study has been made of the cellular content and movement of Ca across the membrane of human red blood cells and the results show that Ca levels in the blood are low and Ca content is high inocytes.
Abstract: 1. A study has been made of the cellular content and movement of Ca across the membrane of human red blood cells.
2. The [Ca] in the cellular contents of fresh red cells is 4·09 × 10-2 mM. The intracellular concentration of free ionic Ca ([Ca2+]) is considered to be less than this value and therefore less than extracellular [Ca2+] under normal conditions.
3. Observation of unidirectional Ca fluxes with 45Ca confirms previous reports of low permeability of the red cell membrane for Ca. After nearly 1 week of loading in the cold, intracellular 45Ca content is 1·8% of extracellular 45Ca content. Appearance in extracellular fluid of 45Ca from coldloaded cells can be considered to arise from two compartments. Efflux of 45Ca from the `slower compartment' is accelerated by the addition of glucose.
4. Starved red cells, incubated at 37° C, after reversible haemolysis for loading with Ca and Mg-ATP, exhibit an outward net transport of Ca against an electrochemical gradient. The transport is associated with the appearance of inorganic phosphate (Pi). Cells treated similarly, but without ATP show no transport and no appearance of Pi.
5. During the initial phase of transport, 1·3 mole Pi appear per mole Ca transported.
6. The transport of Ca from ATP-loaded cells is highly temperature-dependent, with a Q10 of 3·5.
7. Cell membrane adenosine triphosphatase (ATPase) activity of reversibly haemolysed cells is stimulated only by intracellular, and not by extracellular Ca.
8. Neither Ca transport in reversibly haemolysed cells, nor the Ca-Mg activated ATPase of isolated cell membranes is sensitive to Na, K, ouabain or oligomycin.
9. Mg is not transported under the conditions which reveal Ca transport, but Mg appears to be necessary for Ca transport.
10. Sr is transported from reversibly haemolysed Mg-ATP-loaded cells. Sr also can substitute for Ca, but not for Mg, in the activation of membrane ATPase.
11. It is concluded that, in addition to a low passive permeability, an active extrusion mechanism for Ca exists in the human red cell membrane. This extrusion mechanism, in addition to a low passive membrane permeability for Ca, may represent the means by which intracellular Ca content is maintained at a low level. It is suggested that the Ca-Mg activated membrane ATPase and the active transport of Ca are two manifestations of the same process.
510 citations
TL;DR: Reversal potentials (E IPSP) of the inhibitory postsynaptic potential and the membrane resting potentials of lobster muscle fibers were determined with intracellular recording under a variety of ionic conditions.
Abstract: Reversal potentials (EIPSP) of the inhibitory postsynaptic potential and the membrane resting potentials (EM) of lobster muscle fibers were determined with intracellular recording under a variety of ionic conditions. EIPSP is solely dependent on the electromotive force of anionic batteries; i.e., on the electrochemical gradient for a "mobile" fraction of intracellular Cl (Cli) which is considerably smaller than the total intracellular Cl. The active inhibitory membrane is more permeable to certain "foreign" anions in the order NO3 > SCN > Br > Cl. The membrane is impermeable to BrOs, isethionate, and methylsulfate, but is slightly permeable to acetate and propionate. The level of Cli appears to be determined in part by some active (pump?) process and most of the anions studied appear to interfere with the steady-state level of Cli.
65 citations
TL;DR: Concentration gradients across the membranes of living cells for a number of substances, including ions and essential metabolites such as sugars and amino-acids, are maintained through transport processes driven by an energy supply other than the electrochemical gradient of the transported species.
Abstract: IN general, concentration gradients across the membranes of living cells for a number of substances, including ions and essential metabolites such as sugars and amino-acids, are maintained through transport processes driven by an energy supply other than the electrochemical gradient of the transported species. Characteristically, such transport processes involve vectorial transport of the species concerned, a stoichiometric coupling between the energy supply and transport reactions and localization of the transport system in the asymmetric environment which it maintains, usually the membrane phase.
46 citations
TL;DR: The results indicate that the presence of cations profoundly affects the coupling of the energy available in redox reactions to the energy-conserving mechanism in the chloroplast membrane.
43 citations
TL;DR: The evidence suggests that a specific cation pump is not present in chloroplast thylakoid membranes, and it is likely that a proton gradient is the energetic basis for enzyme activation in these experiments, and by inference for the phosphorylation of ADP.
14 citations
TL;DR: The findings suggest that the presence of a contractile principle in the mitochondrial structure may play the role of a regulator of the extent to which generated high-energy bonds are exposed to hydrolysis and may thus constitute a basis for metabolic control.
11 citations
TL;DR: The kinetics of photophosphorylation have been studied in Rhodospirillum rubrum chromatophores and no evidence for a time or intensity lag in photoph phosphorylation was found.
Abstract: The kinetics of photophosphorylation have been studied in Rhodospirillum rubrum chromatophores. No evidence for a time or intensity lag in photophosphorylation was found. An intensity lag could be induced with the uncoupling agent, m-chlorocarbonyl cyanide phenylhydrazone or, in some cases, by aging of the chromatophores.
In chloroplasts, the occurrence of a time and intensity lag in phosphorylation has been correlated with the formation of a proton gradient and quoted as evidence that a proton gradient is a prerequisite of phosphorylation. The significance of the absence of a time and intensity lag in chromatophores is discussed in this context.
10 citations
TL;DR: A method is outlined whereby these relationships can be used to interpret data from lens culture experiments in terms of the various parameters of the pump and leak.
Abstract: The pump-leak system of movement of ions in and out of the lens is described in terms of the parameters governing active transport and passive diffusion across membranes. The relation between the transfer coefficient of the pump and the concentration of the ion being transported (substrate) and inhibitor ion is derived from Michaelis-Menten kinetics. The leak is described in terms of the electrochemical gradient and permeability characteristics of the lens membrane. A method is outlined whereby these relationships can be used to interpret data from lens culture experiments in terms of the various parameters of the pump and leak.
9 citations
TL;DR: In this article, a qualitative confirmation of a prediction derived from the hypothesis that membrane potentials are due to redox potentials, with electron conduction across the membrane through its solid matrix.
7 citations
Journal Article•
TL;DR: The submitochondrial particle system can synthesize ATP by the base-acid transition (proton pulse) only in the presence of ADP and Pi, in spite of the absence of oxidizing substrates and the hexokinase-glucose system, and this phosphorylation is dependent on the span of pH change, and is inhibited by oligomycin and 2, 4-dinitrophenol.
Abstract: l) The submitochondrial particle system can synthesize ATP in the early phase (220 seconds after the accition of ADP) in the presence of sodium succinate and Pi, in spite of the absence of the hexokinase-glucose system, and this phosphorylation is inhibited by oligomycin. 2) The submitochondrial particle system can synthesize ATP by the
base-acid transition (proton pulse) only in the presence of ADP and Pi, in spite of the absence of oxidizing substrates and the hexokinase-glucose system, and this phosphorylation is dependent on the span of pH change,
and is inhibited by oligomycin and 2, 4-dinitrophenol.
3) The role of the proton vector in the oxidative phosphorylation and the proton ejection was discussed from the stand point of a new hypothesis.