Cellular and Immunobiology
Karl H. Pang, Nadir I. Osman, James W.F. Catto, Christopher R. Chapple in Basic Urological Sciences, 2021
TCA (Krebs) cycle takes place within the mitochondria.As acetyl CoA is oxidised, it de-oxidises (reduces) electron carriers NAD and FAD → NADH, FADH2.NAD and FAD pass their electrons into the electron transport chain—oxidative phosphorylation.As electrons pass along the chain, they lose energy, which is used to pump hydrogen ions into inter-membrane space of mitochondria, causing an electrochemical gradient.Hydrogen flows back down the electrochemical current and through membrane enzyme ATP synthase, producing ATP.This process is called chemiosmosis and yields the most ATP from glucose.
The Water Permeability of Intact Subcellular Organelles
Gheorghe Benga in Water Transport in Biological Membranes, 1989
The internal aqueous space of thylakoids does not contain a well-defined impermeant osmoticum, but rather exists in vivo in a collapsed form shown schematically in Figure 8. The lumen of intact thylakoids contains a variety of simple semipermeable monovalent and divalent ions, particularly H+, Na+, K+, Mg2+, and Cl–, which move in response to membrane potentials generated by the light-driven electron transport reactions.50 Chemiosmotic coupling of the pH gradient, formed as a result of electron transport, to the synthesis of ATP, which is a primary storage form of free energy, requires that the thylakoid membrane in vivo forms an osmotic boundary which prevents diffusive dissipation of the light-driven pH gradients for periods of many minutes.
Whole-Body Regulation of Energy Expenditure, Exercise Fuel Selection, and Dietary Recommendations
Peter M. Tiidus, Rebecca E. K. MacPherson, Paul J. LeBlanc, Andrea R. Josse in The Routledge Handbook on Biochemistry of Exercise, 2020
Oxidative Phosphorylation: At rest or with exercise below the respiratory threshold (∼60%–70% V˙O2max), aerobic glycolysis predominates. Here, pyruvic acid enters the mitochondria rather than being reduced to lactic acid and is converted into acetyl-CoA by the action of the pyruvate dehydrogenase complex, making the electron carrier nicotinamide adenine dinucleotide (NADH) available, as it is not needed to form lactic acid. The acetyl-CoA enters the citric acid cycle, where additional NADH and another electron carrier (FADH2), CO2, and a small amount of ATP (substrate phosphorylation) are formed. Ultimately, these carriers pass electrons along the electron transport chain (ETC), also located within the mitochondria, resulting in ATP synthesis, utilizing O2, and forming H2O as an end product. Since the 1960s this electron carrier oxidation coupling to ATP synthesis (chemiosmotic theory; 42) has been the prevailing explanation underlying how oxidative phosphorylation works, but data are accumulating that the torsional theory may more accurately explain the detail of this key step in oxidative metabolism (2, 45). Finally, aerobic metabolism predominates at rest and with low-to-moderate exercise intensities until the rate of pyruvic acid formation from accelerated glycolysis exceeds its maximal removal rate as acetyl-CoA into the citric acid cycle, at which point anaerobic glycolysis ramps up and muscle lactic acid production increases rapidly.
Evaluation of the antimicrobial mechanism of biogenic selenium nanoparticles against Pseudomonas fluorescens
Published in Biofouling, 2023
Ying Xu, Ting Zhang, Jiarui Che, Jiajia Yi, Lina Wei, Hongliang Li
ATP is an important energy molecule for all living organisms and it plays a vital role in a variety of physiological processes such as respiration, metabolism, and enzymatic reactions (Li et al. 2016). Under normal circumstances, intracellular ATP levels remain in a stable state. However, the disruption of cell homeostasis and integrity may cause changes in intracellular ATP concentrations. Compared with the control group, it was found that the intracellular ATP concentrations decreased significantly after treatment with SeNPs (p < 0.05), and the extracellular ATP concentrations showed an increasing trend, among which 2 × MIC of SeNPs led to the greatest depletion (Figure 6). This depletion of cellular ATP indicated an impaired energy metabolic pathway, which in turn might impede ATP synthesis. On the other hand, SeNPs increased the cell membrane permeability, resulting in leakage of intracellular protons, so that the inside and outside of the cell membrane formed a proton gradient difference. According to the chemiosmosis theory, this gradient difference is the electromotive potential of the proton. The leakage of the proton hindered the synthesis of ATP, leading to the reduction of the intracellular ATP content (Jung et al. 2015).
A look into the use of Raman spectroscopy for brain and breast cancer diagnostics: linear and non-linear optics in cancer research as a gateway to tumor cell identity
Published in Expert Review of Molecular Diagnostics, 2020
Halina Abramczyk, Beata Brozek-Pluska, Arkadiusz Jarota, Jakub Surmacki, Anna Imiela, Monika Kopec
First, we must understand intracellular retinoid metabolism in brain cancer cells. Vitamin A plays an important role in cellular signal transduction in many vital processes. Proton gradient triggers the synthesis ATP. There are two types of generation of proton gradient: the light-activated mechanism in vision processes (rhodopsin family),the electron transport chain forms a proton gradient across the inner mitochondrial membrane, which drives the synthesis of ATP via chemiosmosis.
The role of short-chain fatty acids in the interplay between gut microbiota and diet in cardio-metabolic health
Published in Gut Microbes, 2021
Ana Nogal, Ana M. Valdes, Cristina Menni
Propionate can be synthesized through three different biochemical pathways, namely succinate, acrylate, and propanediol pathway.83 In the succinate pathway, the primitive electron transfer chain using phosphoenolpyruvate (PEP) can be utilized to generate propionate.84 Specifically, PEP is carboxylated to oxalacetate, and then oxalacetate is sequentially converted into malate and fumarate. The latter accepts electrons from NADH using a fumarate reductase and a NADH dehydrogenase, which form a simple electron-transfer chain. The NADH dehydrogenase transport protons across the cell membrane. These protons are utilized for chemiosmotic ATP synthesis. Likewise, succinate is generated as a result of the fumarate reductase. When the carbon dioxide partial pressure is low, succinate is transformed to methylmalonate, which leads to propionate and carbon dioxide. The latter can be recycled for the PEP carboxylation, repeating the process. Bacteroidetes85 and several Firmicutes belonging to the Negativicutes class86 use this pathway for the propionate formation. Besides, acrylate pathway can be used to reduce lactate to propionate by a lactoyl-CoA dehydratase.80 This pathway is only present in a very reduced number of gut bacteria, including Coprococcus catus.83 Lastly, 1,2-propanediol can be formed from deoxy sugars such as rhamnose and fucose in the propanediol pathway. Likewise, 1,2-propanediol is sequentially converted into propionaldehyde and propionyl-CoA, which leads to the propionate formation.87Salmonella enterica serovar Typhimurium88 and R. inulinivorans89 are bacteria utilizing this pathway, just as Akkermansia municiphilla which appears to be the major propionate-producing species.90
Related Knowledge Centers
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