Glycolysis - a 10-step biochemical pathway where one glucose molecule (6 C) is split into 2 pyruvate molecules (3 C). To begin the process, 2 ATP must be invested. The energy released by the reactions is captured in the form of 4 ATP molecules and the high energy electrons are trapped in the reduction of 2 NAD molecules to NADH. Say no to plagiarism. Get a tailor-made essay on “Why Violent Video Games Should Not Be Banned”? Get the Original Essay Preparatory PhaseThe preparatory phase is the stage in which there is consumption of ATP and is also known as the investment phase. The payment phase is where ATP is produced. The first five stages of the glycolysis reaction are called the preparatory or investment phase. This step uses energy to convert the glucose molecule into two three-carbon sugar molecules. Step 1 The first step in glycolysis is phosphorylation. This step, glucose is phosphorylated by hexokinase enzymes. 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) + ADPStep 2The second step of glycolysis is an isomerization reaction. In this reaction, glucose-6-phosphate is rearranged to fructose-6-phosphate by the enzyme glucose phosphate isomerase. It is a reversible reaction under normal conditions of the cell.Glucose-6-phosphate (C6H11O6P1) + Phosphoglucoisomerase â†' Fructose-6-phosphate (C6H11O6P1)Step 3In the third step of glycolysis a reaction takes place of phosphorylation. In this step, the enzyme phosphofructokinase is transferred to a phosphate group to form fructose 1,6-bisphosphate. Another ATP molecule is used in this step.Fructose 6-phosphate (C6H11O6P1) + phosphofructokinase + ATP â†' Fructose 1,6-bisphosphate (C6H10O6P2) + ADPStep 4This step in glycolysis is a destabilization step, where the The action of the enzyme aldolase splits fructose 1,6-bisphosphate into two sugars. These sugars are isomers of each other, they are dihydroxyacetone phosphate and glyceraldehyde phosphate. Fructose 1,6-bisphosphate (C6H10O6P2) + aldolase â†' Dihydroxyacetone phosphate (C3H5O3P1) + glyceraldehyde phosphate (C3H5O3P1)Step 5Step 5 of glycolysis is an interconversion reaction. Here, the enzyme triose phosphate isomerase interconverts dihydroxyacetone phosphate and glyceraldehyde phosphate molecules. Dihydroxyacetone phosphate (C3H5O3P1) – Glyceraldehyde phosphate (C3H5O3P1) Profitability phase The second phase of glycolysis is known as the profitability phase of glycolysis. This phase is characterized by a gain of the energy-rich molecules ATP and NADH.Step 6This glycolysis step is a dehydrogenation step. The enzyme triose phosphate dehydrogenase dehydrogenates glyceraldehyde 3-phosphate and adds an inorganic phosphate to form 1,3-bisphosphoglycerate. First, enzymatic action 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 the two 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, where the enzyme phosphoglycerokinase transfers a phosphate group from 1,3-bisphosphoglycerate. Phosphate is transferred to ADP to form ATP. This process produces two molecules of3-phosphoglycerate and two ATP molecules. 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 step of glycolysis is a mutase step, occurs in the presence of the enzyme phosphoglyceratemutaser. This enzyme moves the phosphate from the 3-phosphoglycerate molecule at the third carbon position to the second carbon position, resulting in the formation of 2-phosphoglycerates. 2 molecules of 3-phosphoglycerate (C3H5O4P1) + phosphoglyceromutase â†' 2 molecules of 2- Phosphoglycerate (C3H5O4P1)Step 9This step of glycolysis is a lyase reaction, which occurs in the presence of enolase enzyme. In this reaction, the enzyme removes a water molecule from 2-phosphoglycerate to form phosphoenolpyruvic acid (PEP) 2 molecules of 2-phosphoglycerate (C3H5O4P1) + enolase â†' 2 molecules of phosphoenolpyruvic acid (PEP) (C3H3O3P1 ) + H2OStep 10This is the final step of glycolysis which is a phosphorylation step at the substrate level. In the presence of the enzyme pyruvate kinase, there is a transfer of an inorganic phosphate molecule from the phosphoenol pyruvate molecule to ADP 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, hereby producing two molecules of ATP per molecule of glucoseReaction This links glycolysis to the Krebs cycle. Pyruvate molecules are decarboxylated (they lose a carbon dioxide molecule) in the mitochondria. Pyruvate molecules are oxidized and converted to acetylcoenzyme A, commonly 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 (Link Reaction )Oxidation of pyruvate - 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. Attached to the 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 of the original glucose into CO2, produces 1 ATP, and traps high-energy electrons in 3 NADH and 1 FADH. by Acetyl Co-A.Acetyl CoA + 3 NAD + FAD + ADP + HPO4-2 —————> 2 CO2 + CoA + 3 NADH+ + FADH+ + ATPReaction 1: Formation of CitrateThe first reaction of the cycle is the condensation of l acetyl-CoA with oxaloacetate to form citrate, catalyzed by citrate synthase. Once oxaloacetate is joined to acetyl-CoA, a water molecule attacks the acetyl, resulting in the release of coenzyme A from the complex. Reaction 2: Formation of isocitrateCitrate is rearranged to form an isomeric form, isocitrate by an enzyme aconitase. In this reaction, a water molecule is removed from the citric acid and then put back in 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 gives the molecule isocitrate. Reaction 3: Oxidation of isocitrate to a-ketoglutarate In this step, isocitrate dehydrogenase catalyzes the oxidative decarboxylation of isocitrate to form a-ketoglutarate. In the reaction, we observe 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 yield alpha-ketoglutarate. Reaction 4: Oxidation of a-ketoglutarate to succinyl-LeCoAAlpha-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 released energy is used to make guanosine triphosphate (GTP) from guanosine diphosphate (GDP) and Pi by substrate-level phosphorylation. GTP can then be used to make ATP. The enzyme succinyl-CoA synthase catalyzes this reaction in the citric acid cycle. Reaction 6: Oxidation of succinate to fumarate Succinate 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 malateThe reversible hydration of fumarate to L-malate is catalyzed by fumarase (fumarate hydrate). Fumarase continues the rearrangement process by adding hydrogen and oxygen into the substrate that had previously been removed. Reaction 8: Oxidation of malate to oxaloacetateMalate 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 during glycolysis, oxidation of pyruvate and the Krebs cycle are used to produce ATP by chemiosmosis. O2 is the final acceptor for high energy electrons. In eukaryotes, glycolysis occurs in the cytoplasm, pyruvate oxidation, Krebs cycle and electron transport system occur in the mitochondrion. This route is the most efficient method of producing energy. The initial substrates of this cycle are the final products obtained by other routes. Pyruvate, resulting from glycolysis, is captured by the mitochondria, where it is oxidized via the Krebs/citric acid cycle. The substrates required for the pathway are NADH (nicotinamide adenine dinucleotide), succinate, and molecular oxygen. NADH acts as the first 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 to the water molecule (H2O). Each enzymatic 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 as well as a pH potential 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 balance. While pumping the proton into the matrix, it also carries out the phosphorylation of ADP (adenosine diphosphate) to produce ATP molecules. Complex I - NADH-coenzyme Q oxidoreductase Reduced coenzyme NADH binds to this complex and functions to reduce coenzyme Q10. This reaction yields electrons, which are then transferred through this complex using the FMN (Flavin mononucleotide) and a series of Fe-S (iron-sulfur) clusters. The transport of these electrons causes the transfer of protons across the membrane into the intermembrane space.Complex II -.