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Skeletal Muscle
Published in Nassir H. Sabah, Neuromuscular Fundamentals, 2020
The glucose involved in glycolysis usually comes from the bloodstream, but in muscle cells, in particular, it can come from glycogen. This is an important form of energy storage in the body, second only to fat cells, or adipose tissue. Glycogen is a large, branched polymer of glucose and is synthesized using ATP, mainly in liver and muscle cells. Under aerobic conditions, one glucose molecule produces 6 ATP molecules from glycolysis and 30 ATP molecules in two turns of the citric acid cycle, one turn for each pyruvate molecule, which makes a total of 36 ATP molecules. Under anaerobic conditions, one glucose molecule produces 2 ATP and two lactate molecules. The rate of production of ATP is regulated by the concentrations of ATP and ADP. As the concentration of ATP falls, and that of ADP rises, the citric acid cycle moves at a faster rate. As more pyruvate is used, glycolysis also proceeds at a faster rate.
Turfgrass Physiology and Environmental Stresses
Published in L.B. (Bert) McCarty, Golf Turf Management, 2018
Glycolysis is essentially an inefficient process if considered as a free-standing oxidative pathway. Its end product, pyruvate, contains only slightly less energy than the starting carbohydrate material. Under aerobic conditions, the pyruvate from glycolysis is channeled to the mitochondria, where it is oxidized to form the NADH, FADH2, ATP, and carbon intermediates used in other metabolic reactions such as the synthesis of amino acids necessary for protein synthesis. Such a process is referred to as the citric acid cycle, the tricarboxylic acid cycle (TCA cycle), or the Krebs cycle (named after Hans Krebs, the discoverer). Pyruvate is converted into acetyl-CoA, which is combined with a four-carbon compound (OAA) to form citric acid or citrate (hence, the other designated name). By the end of two cycle turns, acetyl-CoA is completely oxidized into CO2 and H2O, producing NADH and FADH2. The high-energy compounds from the Krebs cycle (NADH and FADH2) are converted to ATP through a series of O2-dependent electron transfers. This mitochondrial process is the ATP-producing electron transport chain. Collectively, the electron transport chain and the synthesis of ATP are referred to the final step of respiration called oxidative phosphorylation. Glucose oxidation via glycolysis and the Krebs cycle in combination with mitochondrial activities yields a net sum of 36 molecules of ATP compared to only 2 molecules through glycolysis alone.
Applications in Biology
Published in Gabriel A. Wainer, Discrete-Event Modeling and Simulation, 2017
The Krebs cycle, also called the tri-carboxylic acid (TCA) cycle and the citric acid cycle (CAC), oxidizes pyruvate formed during the glycolysis pathway into CO2 and H2O. This cycle is a series of chemical reactions of central importance in all living cells that utilize oxygen. The citric acid cycle takes place within the mitochondria in eukaryotes and within the cytoplasm in prokaryotes. For each turn of the cycle, 12 ATP molecules are produced—one directly from the cycle and 11 from the oxidation of the three NADH and one FADH2 molecules produced by the cycle by oxidative phosphorylation [10]. Glucose is converted by glycolysis into pyruvate. Pyruvate enters the mitochondria, linking glycolysis to the Krebs cycle. This step (step A) is also called the bridging step. Pyruvate dehydrogenase—a complex of three enzymes and five coenzymes—oxidizes pyruvate using NAD+ to form acetyl CoA, NADH, and CO2.
Microbial fuel cells: a sustainable solution for bioelectricity generation and wastewater treatment
Published in Biofuels, 2019
Har Mohan Singh, Atin K. Pathak, Kapil Chopra, V.V. Tyagi, Sanjeev Anand, Richa Kothari
Microorganisms can use a wide spectrum of organic compounds (carbohydrates, proteins, lipids) as carbon and energy sources. These compounds can perform as electron donors in citric acid chain reactions and form energy carrier adenosine triphosphate (ATP) molecules before cyclic chain reactions. The conglomerated carbohydrates, proteins and lipids break into their constituting monomers and form acetyl coenzyme A (CoA) by glycolysis. The CoA molecule initiates the citric acid cycle and oxidation reactions occur jointly with reduction of nicotinamide adenine dinucleotide (NAD+) and flavin adenine dinucleotide (FAD) and form nicotinamide adenine dinucleotide (NADH) and flavin adenine dinucleotide (FADH2) as electron carriers. The citric acid cycle is completed in the cytoplasm and cell membrane with the assistance of electron carriers NADH and FADH2 (Figure 2). The cell membrane passes to terminal electron acceptor through various complex membrane intermediates and ATP synthase transmembrane protein is used to convert adenosine diphosphate (ADP) to ATP. These ATP molecules act as the chemical currency of living organisms and the production process represents respiration. In the anodic compartment, a bacterial cell replaces an electrode as the terminal electron acceptor. The mechanism of the cell membrane is shown in Figure 3 [11].
Evaluation of inflammatory processes by FTIR spectroscopy
Published in Journal of Medical Engineering & Technology, 2018
Laís Morandini Rodrigues, Luís Felipe das Chagas e Silva Carvalho, Franck Bonnier, Ana Lia Anbinder, Herculano da Silva Martinho, Janete Dias Almeida
The band at 1080 cm−1 can also be attributed to glycogen [24,25]. It is known that this molecule is linked to the production of energy. When needed, glycogen is broken down through the process of glycolysis, generating pyruvate, which is then metabolised to form acetyl-CoA. This molecule fuels the citric acid cycle with the accompanying production of ATP molecules [26]. In their study, Weisberger and Fischer [27] showed that alteration of glycogen metabolism and phosphorylation of related proteins can be the underlying causes of keratinisation in oral mucosa, while Goltz et al. [28] attributed the increase of glycogen to increased cell differentiation in carcinoma. This is an important property for the classification of the disease. In our case, we believe that an increase in the quantity of this molecule can be associated with the increase of the cellular proliferation, which are fibroblastic cells and the increase of the production and secretion of collagen, which requires an extra charge of energy.