Glycolysis - a 10-step biochemical pathway in which one molecule of glucose (6 C) is split into 2 molecules of pyruvate (3 C). To start the process you need to invest 2 ATP. The energy released by the reactions is captured in the form of 4 molecules of ATP, and the high-energy electrons are trapped in the reduction of 2 molecules of NAD to NADH. Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get an original essay Preparatory Phase The preparatory phase is the phase where the consumption of ATP takes place and is also known as the investment phase. The pay-off phase is where ATP is produced. The first five steps of the glycolysis reaction are known as the preparatory phase or investment phase. This step consumes energy to convert the glucose molecule into two three-carbon sugar molecules. Phase 1 Phase one of glycolysis is phosphorylation. In this step glucose is phosphorylated by the enzyme hexokinase. In this process, the ATP molecule is consumed. A phosphate group from ATP is transferred to glucose molecules to produce glucose-6-phosphate.Glucose (C6H12O6) + hexokinase + ATP â†' Glucose-6-phosphate (C6H11O6P1) + ADPSatep 2The second step of glycolysis is a reaction of isomerization. In this reaction, glucose-6-phosphate is rearranged into fructose-6-phosphate by the enzyme glucose-phosphate isomerase. This is a reversible reaction under normal cell conditions. Glucose-6-phosphate (C6H11O6P1) + phosphoglucoisomerase †' Fructose-6-phosphate (C6H11O6P1) Phase 3In the third phase of glycolysis there is a phosphorylation reaction. In this step, the enzyme phosphofructokinase is transferred to a phosphate group to form fructose 1,6-biphosphate. Another ATP molecule is used in this step. Fructose 6-phosphate (C6H11O6P1) + phosphofructokinase + ATP â†' Fructose 1,6-biphosphate (C6H10O6P2) + ADPSatedium 4This phase of glycolysis is a destabilization phase, in which the action of the enzyme aldolase takes place and divides fructose 1, 6-biphosphate in two sugars. These sugars are isomers of each other, they are dihydroxyacetone phosphate and glyceraldehyde phosphate. Fructose 1,6-biphosphate (C6H10O6P2) + aldolase †' dihydroxyacetone phosphate (C3H5O3P1) + glyceraldehyde phosphate (C3H5O3P1) Step 5Step 5 of glycolysis is an interconversion reaction. Here, the enzyme triose phosphate isomerase interconverts the molecules dihydroxyacetone phosphate and glyceraldehyde phosphate. Dihydroxyacetone phosphate (C3H5O3P1) â†' Glyceraldehyde phosphate (C3H5O3P1) Profit phase The second phase of glycolysis is known as the profit phase of glycolysis. This phase is characterized by a gain of the energy-rich molecules ATP and NADH. Phase 6This phase of glycolysis is a dehydrogenation phase. The enzyme triose phosphate dehydrogenase dehydrogenates glyceraldehyde 3-phosphate and adds an inorganic phosphate to form 1,3-bisphosphoglycerate. First, the action of the enzyme transfers an H- (hydrogen) from glyceraldehyde phosphate to NAD+ which is an oxidizing agent to form NADH. The enzyme also adds an inorganic phosphate from the cytosol to glyceraldehyde phosphate to form 1,3-bisphosphoglycerate. This reaction occurs with both molecules produced in the previous step.2 Glyceraldehyde phosphate (C3H5O3P1) + Triose phosphate dehydrogenase + 2H- + 2P + 2NAD+ â†' two 1,3-bisphosphoglycerate (C3H4O4P2) + 2NADH + 2H+Step 7Step 7 of Glycolysis is a substrate-level phosphorylation step, in which the enzyme phosphoglycerokinase transfers a phosphate group from 1,3-bisphosphoglycerate. Phosphate is transferred to ADP to form ATP. This process produces two molecules of 3-phosphoglycerate molecules and two molecules of ATP. There are two molecules of ATP synthesized in this step of glycolysis.2 molecules of 1,3 bisphosphoglycerate (C3H4O4P2)+phosphoglycerokinase + 2 ADP â†' 2 molecules of 3-phosphoglycerate (C3H5O4P1) + 2 ATPStep 8This phase of glycolysis is a mutase phase, it occurs in the presence of the enzyme phosphoglyceratomutase. This enzyme moves phosphate from the 3-phosphoglycerate molecule found in the third carbon position to the second carbon position, this results in the formation of 2-phosphoglycerate.2 3-phosphoglycerate molecules (C3H5O4P1) + phosphoglyceromutase â†' 2 molecules of 2- Phosphoglycerate (C3H5O4P1) Step 9 This step of glycolysis is a lyase reaction, which occurs in the presence of the enzyme enolase. In this reaction, the enzyme removes one molecule of water from 2-phosphoglycerate to form phosphoenolpyruvic acid (PEP)2 molecules of 2-phosphoglycerate (C3H5O4P1) + enolase †' 2 molecules of phosphoenolpyruvic acid (PEP) (C3H3O3P1) + H2OStep 10This is the final stage of glycolysis which is a phosphorylation step at the substrate level. In the presence of the enzyme pyruvate kinase, the transfer of an inorganic phosphate molecule from the phosphoenol pyruvate molecule to ADP occurs to form pyruvic acid and ATP. This reaction produces 2 molecules of pyruvic acid and two molecules of ATP. 2 molecules of PEP (C3H3O3P1) + pyruvate kinase + 2 ADP â†' 2 molecules of pyruvic acid (C3H4O3) + 2 ATP This reaction marks the end of glycolysis, so producing two molecules of ATP per molecule of glucoseLinking reactionThis links glycolysis to the Krebs cycle.Pyruvate molecules are decarboxylated (lose one molecule of carbon dioxide) in the mitochondria. Pyruvate molecules are oxidized and converted to acetyl coenzyme A, usually abbreviated to acetyl CoA.2CH3COCOO- + 2NAD+ + 2H2O 2CH3COO- + 2NADH + 2H+ + 2CO2The oxidized form of nicotinamide adenine dinucleotide, NAD+, is reduced to its reduced form NADH ( Linking reaction ) Pyruvate oxidation - In a single step, one carbon is removed from pyruvate (3 C) as CO2, leaving 2 of the original carbons attached to coenzyme A. The complex is called acetyl Co A. Bonded to coenzyme A. The complex is called Acetyl Co-A. In this process a molecule of NADH is produced. Krebs CycleKrebs Cycle - An 8-step biochemical pathway that converts all remaining carbons from the original glucose into CO2 and produces 1 ATP and traps high-energy electrons in 3 NADH and 1 FADH for Acetyl Co-A.Acetyl CoA+ 3 NAD + FAD + ADP + HPO4-2 —————> 2 CO2 + CoA + 3 NADH+ + FADH+ + ATPReaction 1: Citrate FormationThe first reaction of the cycle is the condensation of acetyl-CoA with oxaloacetate to form citrate, catalyzed by citrate synthase. Once oxaloacetate combines with acetyl-CoA, a water molecule attacks the acetyl leading to the release of coenzyme A from the complex. Reaction 2: Formation of Isocitrate Citrate is rearranged to form an isomeric form, isocitrate by an aconitase enzyme. In this reaction, a water molecule is removed from the citric acid and then relocated to another location. The overall effect of this conversion is that the –OH group is moved from the 3' position to the 4' position on the molecule. This transformation produces the molecule isocitrate. Reaction 3: Oxidation of isocitrate to a-ketoglutarate. In this step, isocitrate dehydrogenase catalyzes the oxidative decarboxylation of isocitrate to form α-ketoglutarate. In the reaction we see the generation of NADH from NAD. The enzyme isocitrate dehydrogenase catalyzes the oxidation of the –OH group at the 4' position of isocitrate to produce an intermediate from which a carbon dioxide molecule is then removed to produce alpha-ketoglutarate. Reaction 4: Oxidation of α-ketoglutarate to succinyl- CoAAlpha-ketoglutarate is oxidized, carbon dioxide is removed, and coenzyme A is added to form the 4-carbon compound succinyl-CoA.During this oxidation, NAD+ is reduced to NADH + H+. The enzyme that catalyzes this reaction is alpha-ketoglutarate dehydrogenase. Reaction 5: Conversion of succinyl-CoA to succinateCoA is removed from succinyl-CoA to produce succinate. The energy released is used to produce guanosine triphosphate (GTP) from guanosine diphosphate (GDP). and Pi by substrate-level phosphorylation. GTP can then be used to produce ATP. The enzyme succinyl-CoA synthase catalyzes this reactionthe citric acid cycle.Reaction 6: Oxidation of Succinate to FumarateSuccinate is oxidized to fumarate.During this oxidation, FAD is reduced to FADH2. The enzyme succinate dehydrogenase catalyzes the removal of two hydrogens from succinate. Reaction 7: Hydration of fumarate to malate The reversible hydration of fumarate to L-malate is catalyzed by fumarase (hydrated fumarate). Fumarase continues the rearrangement process by adding hydrogen and oxygen into the substrate that was previously removed. Reaction 8: Oxidation of Malate to Oxaloacetate Malate is oxidized to produce oxaloacetate, the starting compound of the citric acid cycle by malate dehydrogenase. During this oxidation, NAD+ is reduced to NADH + H+. Electron Transport ChainElectron Transport Chain: The high-energy electrons trapped in NADH and FADH in glycolysis, pyruvate oxidation, and the Krebs cycle are used to produce ATP through chemiosmosis. O2 is the final acceptor of high-energy electrons. In eukaryotes, glycolysis occurs in the cytoplasm, pyruvate oxidation, the Krebs cycle, and the electron transport system occur in the mitochondrion. This route is the most efficient method of producing energy. The initial substrates for this cycle are the final products obtained from other pathways. Pyruvate, obtained from glycolysis, is absorbed by the mitochondria, where it is oxidized through the Krebs/citric acid cycle. The substrates required for the pathway are NADH (nicotinamide adenine dinucleotide), succinate, and molecular oxygen. NADH acts as the primary electron donor and is oxidized to NAD+ by enzyme complex I, accompanied by the release of a proton from the matrix. The electron is then transported to complex II, which causes the conversion of succinate to fumarate. Molecular oxygen (O2) acts as an electron acceptor in complex IV and is converted into a water molecule (H2O). Each enzyme complex carries out electron transport accompanied by the release of protons into the intermembrane space. The accumulation of protons outside the membrane gives rise to a proton gradient. This high concentration of protons initiates the process of chemiosmosis and activates the ATP synthase complex. Chemiosmosis refers to the generation of an electrical potential and pH across a membrane due to the large difference in proton concentrations. Activated ATP synthase uses this potential and acts as a proton pump to restore concentration equilibrium. As it pumps the proton back into the matrix, it also conducts the phosphorylation of ADP (adenosine diphosphate) to produce ATP molecules. Complex I - NADH-coenzyme Q oxidoreductase The reduced coenzyme NADH binds to this complex and functions to reduce coenzyme Q10. This reaction donates electrons, which are then transferred through this complex using FMN (flavin mononucleotide) and a series of Fe-S (iron-sulfur) clusters. The transport of these electrons results in the transfer of protons across the membrane into the intermembrane space. Complex II - Succinate-Q oxidoreductase This complex acts on succinate produced by the citric acid cycle and converts it to fumarate. This reaction is driven by.