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Introduction to Chemical Reactivity
Published in Caroline Desgranges, Jerome Delhommelle, A Mole of Chemistry, 2020
Caroline Desgranges, Jerome Delhommelle
Maintaining a pH at a given level by adding or removing acids and bases is crucial for living organisms. This is, for instance, the case of the blood pH that, for humans, needs to stay in a very narrow range between 7.35 and 7.45. If the blood pH drops below 7.35, then a condition known as acidosis sets in. If the blood pH becomes greater than 7.45, the corresponding condition is called alkalosis. The key for the organism is to remove the carbon dioxide (or carbonic acid) produced by metabolizing glucose. This is achieved by the lungs which remove CO2 through breathing, and by the kidneys which remove it through urine. If the blood pH is not in the 7.35–7.45 range, there can be either a respiratory condition or a metabolic issue related to a dysfunction of the kidneys.
β
Published in James F. Pankow, Aquatic Chemistry Concepts, 2019
If any amount of strong base is added to any aqueous solution, the pH will go up. Conversely, if any amount of strong acid is added, the pH will go down. Chemists are often interested in knowing how pH-sensitive a system is to incremental addition of strong base or acid; the parameter that quantifies this concept is the buffer intensity β. In the environment, many aquatic organisms depend on the pH of the water to be in some particular range, and deviations from that range cause stress, or in extreme cases, mass die-offs. In the human body, a great many important biochemical reactions are very pH sensitive, so buffering is again extremely important. For humans, nothing makes this point more clearly than noting that human blood needs to be in a very narrow pH range so that pHdependent reactions can proceed at needed rates. For arterial blood, the normal range is 7.35 to 7.45; for venous blood, 7.32 to 7.42. Having recently passed through the lungs, arterial blood is slightly more alkaline because of loss of some metabolically generated CO2 to exhaled air. “Acidosis” is the condition when blood pH is too low, and “alkalosis” is the condition when blood pH is too high. (Acidosis in humans often leads to tachypnea/hyperventilation as a means to off-gas CO2 and raise blood pH.) Most natural water organisms benefit when their aquatic environment is characterized by an adequately large β so as to prevent significant swings in pH due to acid/base additions or losses.
Repeated remote ischaemic preconditioning can prevent acute mountain sickness after rapid ascent to a high altitude
Published in European Journal of Sport Science, 2022
Zhen Wang, Bo Lv, Lin Zhang, Ran Gao, Wenbo Zhao, Lin Wang, Zhaojun Min, Zhen Mi, Yang Song, Jing Zhang, Yabin Yu, Xunming Ji, Junjie Li, Liyong Wu
The precise pathogenic mechanisms underlying AMS remain to be elucidated. Hypoxia likely plays a central role in its pathogenesis (Taylor, 2011). Hypoxia at a high altitude can lead to hypoxemia, and the condition is aggravated by a reduced level of carbon dioxide through respiratory alkalosis and inhibition of the hypoxic ventilatory response (HVR) (Taylor, 2011). Hypoxemia induces the upregulation of hypoxia-inducible factor 1 and vascular endothelial growth factor and the formation of free radicals, which, together with hypoxemia, affect cerebrovascular permeability (Wilson, Newman, & Imray, 2009). A series of compensatory mechanisms, including adenosine production, potassium ion accumulation and nitric oxide release, may facilitate vasodilatation and alleviate cerebral hypoxia, although researchers have proposed that the exaggerated activity of these compensatory mechanisms may contribute to altitude maladaptation (Wilson et al., 2009).
Sodium bicarbonate supplementation and the female athlete: A brief commentary with small scale systematic review and meta-analysis
Published in European Journal of Sport Science, 2022
Bryan Saunders, Luana Farias de Oliveira, Eimear Dolan, Krzysztof Durkalec-Michalski, Lars McNaughton, Guilherme Giannini Artioli, Paul Alan Swinton
Sodium bicarbonate is considered an effective ergogenic supplement (Maughan et al., 2018), with repeated meta-analytical data supporting its use for improving high-intensity exercise capacity and performance (Carr, Hopkins, & Gore, 2011; Christensen, Shirai, Ritz, & Nordsborg, 2017; Matson & Tran, 1993; Peart, Siegler, & Vince, 2012). This is due to an increase in blood pH and circulating bicarbonate concentration (i.e. alkalosis) following ingestion, augmenting the buffering potential of the body. This increased buffering capacity can improve control of exercise-induced metabolic acidosis, characterized by hydrogen ion (H+) accumulation that is detrimental to exercise performance due to its interference with several metabolic and contractile processes (Allen, Lamb, & Westerblad, 2008; Fitts, 1994; Jarvis, Woodward, Debold, & Walcott, 2018; Sundberg, Hunter, Trappe, Smith, & Fitts, 2018).
Normobaric hypoxia training in military aviation and subsequent hypoxia symptom recognition
Published in Ergonomics, 2021
Antti Leinonen, Nikke Varis, Hannu Kokki, Tuomo K. Leino
Hypoxia symptoms can vary from one training exposure to another, and this variation may affect the pilots’ ability to recognise the symptoms. One of the reasons for this may be increased ventilation rates resulting in a combination of hypoxia and hypocapnia (Loeppky et al. 1997; Temme et al. 2017). This combination may lead to respiratory alkalosis, which shifts the O2 dissociation curve to the left. Initially, with decreased O2 tension, unloading of O2 at peripheral tissues is favoured, but in hypoxia and hypocapnia haemoglobin has an increased affinity for O2 and unloads it more reluctantly. Consistent with our findings, others have shown that there is considerable variation in response to hypoxia, and people tend to forget their symptoms of hypoxia (Woodrow, Webb, and Wier 2011).