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Oxidative Phosphorylation— Photosynthesis
Published in Jean-Louis Burgot, Thermodynamics in Bioenergetics, 2019
The electrons of NADH enter into the chain at the level of NADH dehydrogenase. There is a reaction redox between the couples NAD+/NADH E’°(NAD+/NADH) = –0,32V and FMN/FMNH2 E’° (FAD/FADH2) = –0,22V. The FMN is the prosthetic group of the NADH deshydrogenase. (A flavin nucleotide is most of the time bound rather tightly to the protein). They do not transfer electrons by diffusing from one enzyme to another. Rather, they provide a means by which they catalyze electron transfer from a reduced substance to an electron acceptor. One important feature of flavoproteins is the variability in the standard reduction potential E’°. Their range values are about −0,40V to +0, 06V. One admits that, in these circumstances, the standard biological redox potential of the couple FMN/FMN H2 allows the following reaction to spontaneously occur: NADH + H+ + FMN→NAD+ + FMNH2Examples of structures of hemes.
Interfacial Catalysis at Oil/Water Interfaces
Published in Alexander G. Vdlkdv, Interfacial Catalysis, 2002
Plant mitochondria have two membranes: a smooth outer membrane that surrounds a invaginated inner membrane. The respiratory chain of mitochondria is an integral part of the inner mitochondrial membrane. It is composed of four electron-transporting protein complexes (NADH dehydrogenase complex I, succinate dehydrogenase complex II, cytochrome reductase complex III, and cytochrome c oxidase complex IV), ATP synthase (complex V), and the mobile electron carriers ubiquinone and cytochrome c. Plant mitochondria have additional enzymes not found in the mitochondria of animals: the cyanideinsensitive alternative oxidase, an internal rotenone-insensitive NADPH dehydrogenase, and an externally located NADPH dehydrogenase, which do not conserve energy. The alternative oxidase catalyzes the oxidation of ubiquinol to ubiquinone and the reduction of oxygen to water and is inhibited by salicylhydroxamic acid. In some photosynthetic cells the carbohydrates formed during photosynthesis can serve as the Gibbs free energy source for respiration, which leads to ATP synthesis and water and CO2 production. Oxygen reduction, catalyzed by cytochrome c oxidase accounts for a significant portion of the water eliminated from the mitochondria.
Cell Physiology
Published in Wei-Shou Hu, Cell Culture Bioprocess Engineering, 2020
Extraction of the chemical potential energy of NADH and FADH2 takes place through an electron transfer chain residing in the mitochondrial inner membrane (Panel 3.5). The high-energy electrons of NADH and FADH2 enter the electron transport chain to move down the energy ladder, mediated by electron carriers including flavin, the iron-sulfur complex, heme, and copper ions which are embedded in a number of large enzyme complexes such as NADH dehydrogenase. At the end of the electron transfer chain, the electron is received by oxygen which then reacts with a proton to form H2O (Figure 3.4b).
Current approaches for the exploration of antimicrobial activities of nanoparticles
Published in Science and Technology of Advanced Materials, 2021
Nur Ameera Rosli, Yeit Haan Teow, Ebrahim Mahmoudi
Another antimicrobial mechanism of NPs concerns the disruption of the mitochondrial electron transport chain (ETC). The high affinity of Ag NPs and Ag+ for thiol groups in cysteine residues has been reported to interrupt mitochondrial membrane proteins, membrane permeability, and mitochondrial functions [47]. ETCs are a series of protein complexes in the mitochondrial inner membrane that couple redox reactions transferring electrons from electron donors to electron receptors through an electrochemical gradient, thereby generating adenosine triphosphates (ATPs) which are essential for cellular respiration [48]. The four complexes in the ETC are complexes I (nicotinamide adenine dinucleotide (NADH) dehydrogenase), II (succinate dehydrogenase), III (cytochrome c oxidoreductase), and IV (cytochrome oxidase) [48]. NPs can accumulate in the mitochondria, resulting in mitochondrial membrane depolarization and blockage of ETC following exposure to NPs through activation of nicotinamide adenine dinucleotide phosphate (NADPH)-related enzyme [49,50]. The blockage of the ETC will further increase the cellular level of ROS via electron transfer [50]. In one study, Cu NPs have been demonstrated to have the potential to block the functions of complexes I and III on the mitochondrial ETC causing the over-generation of ROS and oxidative stress upon cell membranes [48]. In another study, TiO2 NPs have been demonstrated to disrupt the ETC as evidenced by the down-regulation of cardiolipin (a phospholipid in the mitochondrial inner membrane responsible for maintaining the functions of those ETC complexes) [51].
Antioxidant and cytoprotective effects of avocado oil and extract (Persea americana Mill) against rotenone using monkey kidney epithelial cells (Vero)
Published in Journal of Toxicology and Environmental Health, Part A, 2021
Nelzi Ferreira Queiroz Junior, Jovani Antônio Steffani, Larissa Machado, Pâmela Jéssyca Hoss Longhi, Marco Aurélio Echart Montano, Mathias Martins, Sérgio Abreu Machado, Alencar Kolinski Machado, Francine Carla Cadoná
Regarding the pro-oxidative effect of rotenone, several investigators reported that this pesticide promoted oxidative stress since once inside the cell, rotenone crosses the mitochondrial membrane and binds to the enzyme NADH dehydrogenase, present in complex I of the mitochondrial respiratory chain (Jiang et al. 2017; Siddiqui et al. 2013; Wang et al. 2021), producing mitochondrial dysfunction, adenosine triphosphate (ATP) deficiency and accumulation of ROS (Niu et al. 2020; Radad et al. 2019). Thus rotenone is considered a potent inhibitor of complex I, also known as NADH:ubiquinone oxidoreductase (Feng et al. 2015; Seoposengwe, van Tonder, and Steenkamp 2013). Excess ROS levels produce damage to nucleic acids, lipids, and proteins, leading to a progressive decline in physiological functions, which are associated with the development of several diseases (Beckhauser, Francis-Oliveira, and De Pasquale 2016; Kurpik et al. 2021; Sanders and Greenamyre 2013).