Glucose Metabolism

• Glucose is the only source used by brain under starvation conditions
• The major pathways in carbohydrate metabolism is glycolysis
• Energy performing pathways of carbohydrate metabolism include glycolysis, glucogenesis, glycogenesis, glycogenolysis, gluconeogenesis, and pentose pathway
• Glycolysis is the catabolic pathway, while gluconeogenesis is an anabolic pathway
• Gluconeogenesis is the process of synthesizing glucose from noncarbohydrate starting materials like pyruvate, lactate, amino acids, and glycerol
• Glycolysis is a Catabolic process that produces some 2 ATP and 2 NADH
• The stages of glycolysis include Energy investment, and energy producing
• Reaction 1 in glycolysis is where the hexokinase enzyme with magnesium uses the first ATP, producing Glucose 6 phosphate and ADP
• Hexokinase would trap glucose in the cell and begins glycolysis. It also transfers phosphate from ATP
• The presence of magnesium help in shielding the phosphate and initiates nucleophilic attack of the phosphorous
• Reaction 2 involves phosphoglucose isomerase producing Fructose 6 phosphate
• Reaction 3 is where the enzyme phosphofructokinase and 2nd substrate Mg2+ yields Fructose 1,6 bisphosphate
• Phosphofructokinase is an allosteric enzyme that is stimulated by AMP and inhibited by ATP and citrate
• Reaction 4 is where Type A Aldolase converts Fructose 1.6 Bisphosphate to 3-Carbon Glyceralehyde 3 phosphate and dihydroxyacetone phosphate
• Reaction 5 involves Triose phosphate isomerase (TIM), isomerizing DHAP to GAP and the end of stage 1
• Reaction 6 involves the oxidation and phosphorylation with glyceraldehyde 3 phosphate dehydrogenase, NAD+ and Pi which forms the first high energy intermediate of 1,3 Bisphosphoglycerate and other products such as NADH and H+
• The source of an inorganic phosphate in reaction 6 could be the ATP that is hydrolyzed
• Reaction 7 is where 1,3-biphosphoglycerate is phosphorylated to ADP by phosphoglycerate kinase and Mg2+ forming 3-Phosphoglycerate, and the first ATP
• Reaction 7 produces the first ATP and since we have two GAP from the reaction, the 2 ATP consumed during the energy storage are compensated
• Reaction 8 involves the enzyme phosphoglycerate mutase which catalyzes rearrangement of functional groups within the molecule forming 2 Phosphoglycerate
• High 2,3 - BPG decreases the oxygen affinity of hemoglobin
• Pyruvate kinase is the last enzyme, which metabolites would build up to be produced...
• Reaction 9 involves enolase through dehydration which forms a second high energy intermediate of phosphoenolpyruvate and H2O
• Reaction 10 is where Phosphoenolpyruvate, a high energy compound phosphorylates with Pyruvate Kinase, ADP, and H+ forming Pyruvate and ATP
• The net reaction of glycolysis is -96kJ/mol
• Homolactic fermentation converts pyruvate to lactate by the enzyme lactate dehydrogenase and releases NAD+
• Homolactic fermentation is produced in the muscle source, and the last step in glycolysis
• The cori cycle is where lactate is produced anaerobically in muscle cells with during strenuous exercise
• After producing lactate during the cori cycle, when passing through blood to the liver, lactate is converted to glucose by gluconeogenesis
• The toxic effects of acetaldehyde in ethanol would produce harmful products in the fetus
• The glycolysis is known as the Embden Meyerhof Parnas pathway
• Glycolysis is a sequence of 10 enzymatic reactions where one molecule of Glucose is converted to 2 molecules of pyruvate with the generation of 2 ATP
• Pyruvate can be converted to lactate, ethanol, acetyl cOA, and even to glucose
• Acetyl CoA is a metabolite of Pyruvate, and a raw material for the synthesis of Fatty acids if Glucose exceeds the needs for the production of energy
• Glycogenolysis is a catabolic pathway, while glycogenesis is a anabolic pathway
• Glucose metabolism can produce ATP to power muscle contractions
• Low O2 can lead to anaerobic metabolism or production of lactic acid or ethanol from pyruvate
• Slow movement or normal production of O2 lead to aerobic metabolism of pyruvate producing more ATP and is completely oxidized to CO2 and H2O until the electron transport chain
• There are 3 reactions which are bypassed in gluconeogenesis comparing to glycolysis
• Lactic acid is produced in the muscle, while ethanol is produced in the yeast