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Biochemistry of Buffering Capacity and Ingestion of Buffers In Exercise and Athletic Performance
Published in Peter M. Tiidus, Rebecca E. K. MacPherson, Paul J. LeBlanc, Andrea R. Josse, The Routledge Handbook on Biochemistry of Exercise, 2020
Bryan Saunders, Guilherme G. Artioli, Eimear Dolan, Rebecca L. Jones, Joseph Matthews, Craig Sale
Hydrogen is the simplest element in nature, formed by a single positively charged proton and a single negatively charged electron. Single hydrogen atoms are, however, not common on earth, since they naturally combine with other elements to form molecules, such as the diatomic gas form of hydrogen (H2) or water (H2O). Water is essential for virtually all known forms of life, since all biochemical reactions require an aqueous medium to occur. Due to its molecular arrangement, in particular the hydrogen side of the molecule being positively charged and the oxygen side of the molecule being negatively charged, water becomes a polar molecule, with a high dielectric constant and it easily forms hydrogen bonds. These characteristics make water an excellent solvent, as the electric charges interact with numerous elements and molecules.
Finding a Target
Published in Nathan Keighley, Miraculous Medicines and the Chemistry of Drug Design, 2020
The elements that are prevalent in organic chemistry are indeed the fundamental building blocks of the cell also. Nature carries out its organic reactions within the aqueous environment inside the cell, with water serving as a solvent. Polar molecules are dissolved; those with functional groups containing electronegative atoms that pull the electron density of the molecule towards themselves are held within the aqueous medium, while non-polar hydrophobic compounds remain separate from the internal cellular solution, known as the cytoplasm. This property of different solubility of biological molecules is crucial to the cell, for it governs how molecules interact and react together and how the cell membrane is formed to give the cell its structure and stability. Many of the functional groups commonly used in organic chemistry are also frequently seen in nature: methyl (CH3), hydroxyl (OH), carboxyl (COOH), and amino (NH2) recur repeatedly in biology. The small organic molecules found in the cell generally contain up to 30 atoms and have many uses in the cell, such as intermediates for deriving energy from food and units to build polymers which comprise the majority of the cells composition.
Alcohols and Aldehydes
Published in Frank A. Barile, Barile’s Clinical Toxicology, 2019
Although a polar molecule, ethanol is a colorless aliphatic hydroxy-hydrocarbon molecule, possessing both water and lipid solubility. Ethanol diffuses across cell membranes easily and is absorbed from the gastrointestinal (GI) tract rapidly. The average apparent volume of distribution (Vd) of ethanol is about 0.6 l/kg, nearly equivalent to that of water. It is thus capable of readily distributing throughout physiologic compartments; particularly, it is able to penetrate the blood–brain barrier and placenta. Because the oxidation of ethanol yields 7.1 kcal/g, sufficient calories can be obtained from ethanol alone for chronic drinkers if the daily intake of ethanol exceeds 5 g/kg of body weight.
Correlations between pore textures of activated carbons and Langmuir constants – case studies on methylene blue and congo red adsorption
Published in Toxin Reviews, 2022
Fadina Amran, Muhammad Abbas Ahmad Zaini
Figure 2 displays the correlations for congo red adsorption. Generally, the capacity increased with increasing pore size and mesopore volume. The capacity and affinity increased as mesopore volume increases from 0.05 to 0.362 cm3/g. However, a decrease in affinity for activated carbon with mesopore volume of 0.725 cm3/g signifies the clog in the pores, so inducing the mass transfer resistance for adsorption deeper into the surface. The molecular aggregation is due to the presence of non-polar molecules in water that disrupts the hydrogen bond network, resulting in a loss of movement and rotational freedom of dye molecules within the hydrophobic structure. The collisional frequency among the molecules to form aggregates increased with increasing concentration, consequently leading to a drastic decrease in adsorption rate (Kunzler et al.2011).
Ion channels and ion homeostasis in the platelet and megakaryocyte
Published in Platelets, 2021
Kirk A. Taylor, Martyn P. Mahaut-Smith
Ion channels represent the main mechanism whereby cells can rapidly influence the concentration of ions within the cytoplasm and organelles. Compared to other cell types, the study of these transmembrane proteins in the platelet and megakaryocyte is still in its infancy. Nevertheless, key roles are becoming apparent for a range of channels which are predominantly permeable to ions other than Ca2+. Furthermore, some pore-forming membrane proteins such as the gap junction family members are also permeable to quite large (<1kDa) molecular weight charged and uncharged molecules. Taylor and colleagues [12] discuss the potential roles for the pannexin and connexin gap junction proteins in regulating thrombus formation and coordinating platelet responses. Being a polar molecule, water also passes slowly across lipid bilayers and its diffusion across cell membranes is mainly controlled by pore-forming proteins known as aquaporins. Procoagulant activity has been associated with membrane ballooning that may arise from influx of water into the cytosol. In their review, Agbani and Poole [13] describe the expression and function of aquaporins in platelets, including genetic and biochemical evidence for at least 5 members of this family of water-permeable channels.
Vesicle formation mechanisms: an overview
Published in Journal of Liposome Research, 2021
According to symmetry and charge distribution, molecules can be roughly divided into two categories, i.e. polar and non-polar. Polar molecules are soluble in a polar solvent (e.g. ethanol in water) and insoluble in a non-polar solvent (e.g. oil in water), and vice versa (Lasic 1993). Some molecules (such as phospholipids, surfactants, and copolymers) contain both polar and non-polar groups, commonly known as amphiphiles. As these amphiphiles possess both hydrophilic and hydrophobic interactions, they can self-assemble and form ordered structures in an aqueous milieu. Depending on amphiphiles molecular shape, their self-assembly in water results in several phases, e.g. some organise into small spherical, globular or cylindrical micelles, while the others appear to assemble into spherical vesicles, bicontinuous cubic phases or planner bilayers (Lasic 1993, Sterling 1993, Guida 2010).