scholarly journals The real limits to marine life: a further critique of the Respiration Index

2013 ◽  
Vol 10 (5) ◽  
pp. 2815-2819 ◽  
Author(s):  
B. A. Seibel ◽  
J. J. Childress
Keyword(s):  
Carbon Dioxide ◽  
Equilibrium Constant ◽  
Synergistic Effects ◽  
Standard Free Energy ◽  
Potential Effect ◽  
Cellular Respiration ◽  
Standard Free Energy Change ◽  
Saturation State ◽  
The Real ◽  
Marine Life

Abstract. The recently proposed "Respiration Index" (RI = log PO2/PCO2) suggests that aerobic metabolism is limited by the ratio of reactants (oxygen) to products (carbon dioxide) according to the thermodynamics of cellular respiration. Here, we demonstrate further that, because of the large standard free energy change for organic carbon oxidation (ΔG° = −686 kcal mol−1), carbon dioxide can never reach concentrations that would limit the thermodynamics of this reaction. A PCO2 to PO2 ratio of 10503 would be required to reach equilibrium (equilibrium constant, Keq = 10503), where ΔG = 0. Thus, a Respiration Index of −503 would be the real thermodynamic limit to aerobic life. Such a Respiration Index is never reached, either in the cell or in the environment. Moreover, cellular respiration and oxygen provision are kinetically controlled such that, within limits, environmental oxygen and CO2 concentrations have little to do with intracellular concentrations. The RI is fundamentally different from the aragonite saturation state, a thermodynamic index used to quantify the potential effect of CO2 on calcification rates, because of its failure to incorporate the equilibrium constant of the reaction. Not only is the RI invalid, but its use leads to incorrect and misleading predictions of the threat of changing oxygen and carbon dioxide to marine life. We provide a physiological framework that identifies oxygen thresholds and allows for synergistic effects of ocean acidification and global warming.

scholarly journals The real limits to marine life: a further critique of the Respiration Index

2012 ◽  
Vol 9 (11) ◽  
pp. 16521-16532 ◽  
Author(s):  
B. A. Seibel ◽  
J. J. Childress
Keyword(s):  
Carbon Dioxide ◽  
Equilibrium Constant ◽  
Synergistic Effects ◽  
Standard Free Energy ◽  
Physiological Model ◽  
Cellular Respiration ◽  
Standard Free Energy Change ◽  
Saturation State ◽  
The Real ◽  
Marine Life

Abstract. The recently proposed "Respiration Index" (RI = log[PO2]/[PCO2]) suggests that aerobic metabolism is limited by the ratio of reactants (R, oxygen) and products (P, carbon dioxide) according to the thermodynamics of cellular respiration. Here we demonstrate that, because of the large standard free energy change for organic carbon oxidation (ΔG° = −686 kcal mol−1), carbon dioxide can never reach concentrations that would limit the thermodynamics of this reaction. A PCO2 to PO2 ratio of 10503 would be required to reach equilibrium (equilibrium constant, Keq = 10503), where ΔG = 0. Thus a respiration index of −503 would be the real thermodynamic limit to aerobic life. Such a Respiration Index is never reached either in the cell or in the environment. Moreover cellular respiration and oxygen provision are kinetically controlled such that, within limits, environmental oxygen and CO2 concentrations have little to do with intracellular concentrations. The RI is fundamentally different from the aragonite saturation state, a thermodynamic index used to quantify the potential effect of CO2 on calcification rates, because of its failure to incorporate the equilibrium constant of the reaction. Not only is the RI invalid, its use leads to incorrect and dangerous predictions of the threat of changing oxygen and carbon dioxide to marine life. We provide a physiological model that identifies oxygen thresholds, and allows for synergistic effects of ocean acidification and global warming.

scholarly journals The nature of carbon dioxide substrate and equilibrium constant of the 6-phosphogluconate dehydrogenase reaction

1969 ◽  
Vol 115 (4) ◽  
pp. 633-638 ◽  
Author(s):  
R. H. Villet ◽  
K. Dalziel
Keyword(s):  
Carbon Dioxide ◽  
Free Energy ◽  
Equilibrium Constant ◽  
Heat Of Reaction ◽  
Phosphogluconate Dehydrogenase ◽  
Sheep Liver ◽  
Dehydrogenase Reaction ◽  
Reductive Carboxylation ◽  
Primary Substrate

1. It was shown that dissolved CO2 and not HCO3− or H2CO3 is the primary substrate for reductive carboxylation with 6-phosphogluconate dehydrogenase from sheep liver. 2. The equilibrium constant of the reaction was measured in solutions of various ionic strengths and at several temperatures, and the free energy and heat of reaction were determined.

The Equilibrium and the Determination of D00 (H—CN)

1975 ◽  
Vol 53 (16) ◽  
pp. 2365-2370 ◽  
Author(s):  
Don Betowski ◽  
Gervase Mackay ◽  
John Payzant ◽  
Diethard Bohme
Keyword(s):  
Free Energy ◽  
Standard Enthalpy ◽  
Transfer Reaction ◽  
Standard Free Energy ◽  
Proton Transfer Reaction ◽  
Enthalpy Change ◽  
Standard Free Energy Change ◽  
Flowing Afterglow ◽  
Standard Enthalpy Change

The rate constants and equilibrium constant for the proton transfer reaction [Formula: see text] have been measured at 296 ± 2 K using the flowing afterglow technique: kforward = (2.9 ± 0.6) × 10−9 cm3molecule−1s−1, kreverse = (1.8 ± 0.4) × 10−10 cm3 molecule1 s−1, and K = 16 ± 2. The measured value of K corresponds to a standard free energy change, ΔG296°, of −1.6 ± 0.1 kcal mol−1 which provides values for the standard enthalpy change, ΔH298°= −1.0 ± 0.2 kcal mol−1, the bond dissociation energy, D00(H—CN) = 124 ± 2 kcal mol−1, and the proton affinity, p.a.(CN−) = 350 ± 1 kcal mol−1.

Carbon dioxide inhalation causes pulmonary inflammation

2009 ◽  
Vol 296 (4) ◽  
pp. L657-L665 ◽  
Author(s):  
Mohammad Abolhassani ◽  
Adeline Guais ◽  
Philippe Chaumet-Riffaud ◽  
Annie J. Sasco ◽  
Laurent Schwartz
Keyword(s):  
Carbon Dioxide ◽  
Nuclear Translocation ◽  
Rnase Protection Assay ◽  
Airway Hyperreactivity ◽  
Cellular Respiration ◽  
Rnase Protection ◽  
Monocyte Chemoattractant Protein 1 ◽  
Enhanced Production

The aim of this study was to assess whether one of the most common poisons of cellular respiration, i.e., carbon dioxide, is proinflammatory. CO2 is naturally present in the atmosphere at the level of 0.038% and involved in numerous cellular biochemical reactions. We analyzed in vitro the inflammation response induced by exposure to CO2 for 48 h (0–20% with a constant O2 concentration of 21%). In vivo mice were submitted to increasing concentrations of CO2 (0, 5, 10, and 15% with a constant O2 concentration of 21%) for 1 h. The exposure to concentrations above 5% of CO2 resulted in the increased transcription (RNase protection assay) and secretion (ELISA) of proinflammatory cytokines [macrophage inflammatory protein-1α (MIP-1α), MIP-1β, MIP-2, IL-8, IL-6, monocyte chemoattractant protein-1, and regulated upon activation, normal T cell expressed, and, presumably, secreted (RANTES)] by epithelial cell lines HT-29 or A549 and primary pulmonary cells retrieved from the exposed mice. Lung inflammation was also demonstrated in vivo by mucin 5AC-enhanced production and airway hyperreactivity induction. This response was mostly mediated by the nuclear translocation of p65 NF-κB, itself a consequence of protein phosphatase 2A (PP2A) activation. Short inhibiting RNAs (siRNAs) targeted toward PP2Ac reversed the effect of carbon dioxide, i.e., disrupted the NF-κB activation and the proinflammatory cytokine secretion. In conclusion, this study strongly suggests that exposure to carbon dioxide may be more toxic than previously thought. This may be relevant for carcinogenic effects of combustion products.

A mathematical model of the carbon metabolism in photosynthesis. Difficulties in explaining oscillations by fructose 2, 6-bisphosphate regulation

1989 ◽  
Vol 237 (1289) ◽  
pp. 389-415 ◽  
Keyword(s):  
Mathematical Model ◽  
Active Sites ◽  
Starch Synthesis ◽  
Standard Free Energy ◽  
Atp Synthesis ◽  
Rate Equations ◽  
Standard Free Energy Change ◽  
Sucrose Synthesis ◽  
Carbon Reduction ◽  
Fructose 2

A mathematical model of the pentosephosphate carbon reduction (PCR) cycle is presented. The internal structure of the model is consistent with and complements the known biochemical pathways in the PCR cycle, together with starch and sucrose synthesis. Individual enzymes are described by maximum rate ( V m ), standard free energy change (Δ G´ 0 ) and Michaelis constant ( K m ) values as parameters and rate-equations, sym­metrical for the direct and reverse reactions. Enzymic control is included in the starch synthesis pathway (activation by phosphoglycerate (PGA)), inhibition by inorganic phosphate) and in the reactions of sucrose synthesis based on fructose 2, 6-bisphosphate (F2, 6BP) as a metabolite con­trolling the cytosolic fructose bisphosphatase (FBPase) activity. The phosphate translocator carries out the exchange of triose phosphates, orthophosphate and PGA. Ionic forms of metabolites are calculated in relation to pH and assumed to be the actual reacting substances. The significant concentration of the active sites of ribulose 1, 5-bisphosphate (RuBP) carboxylase is taken into account. Light reactions are included only in the form of an ATPase the Δ G´ 0 of which is shifted towards ATP synthesis by the existing proton gradient. The behaviour of the model was studied with the aim of reproducing oscillations in photosynthesis. It is concluded that oscillations in photosynthesis cannot be caused by the fructose 2, 6-bisphosphate control of sucrose synthesis alone, but that an additional control of photosynthetic rate must also be involved.

scholarly journals Comprehensive Assimilation of Fire Suppression Modeling and Simulation of Radiant Fire by Water and Its Synergistic Effects with Carbon Dioxide

Energies ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 5850
Author(s):  
Hassan Raza Shah ◽  
Kun Wang ◽  
Xu Qing Lang ◽  
Jing Wu Wang ◽  
Jing Jun Wang ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Synergistic Effects ◽  
Fire Suppression ◽  
Water Mist ◽  
Pool Fire ◽  
Water Suppression ◽  
Water Droplets ◽  
Film Forming ◽  
The Difference ◽  
Suppression Effects

Recently, water has been employed as a supportive agent for the preparation of multiple suppressing agents including aqueous film forming foams (AFFF), which is combined with different kinds of gases for its various applications. In this study, the water mist is chosen for the gas-suppressing agent such as carbon dioxide. Our work investigated the suppression effects of water droplets on the n-heptane pool fire, and its mixture with carbon dioxide, respectively. The size and frequency of droplets with their effect on temperature and suppression was compared to observe the difference in the suppression. Initially, it was found that the droplets having a larger droplet size were found to be more efficient as compared to the smaller droplets with respect to the heat release rate, temperature, and radiation. Afterwards, a mixture of water droplets and carbon dioxide was simultaneously discharged to compare the difference between these two suppressing agents. It was found that the synergistic effect of the mixture has higher advantages over the use of only water suppression. It helps reduce the hot gases that surround the pool fire and allows the water mist to travel efficiently towards the fuel. Both suppression mechanisms were set to similar initial parameters that lead to different outcomes.

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