 In this video I will describe the overall result in terms of molecules produced in the breakdown of glucose by glycolysis. Glycolysis is a catabolic pathway that converts one 6-carbon glucose molecule into two 3-carbon pyruvate molecules and will generate two molecules of ATP and two molecules of NADH. While glycolysis generates ATP that the cell can use in order to sustain life, the first phase of glycolysis is the energy consuming phase that will consume two molecules of ATP in order to fuel endogonic chemical reactions. Following the energy consuming phase, coupling of phosphorylation with oxidation will transfer high energy electrons onto the oxidizing agent NAD+, forming the high energy electron carrier molecules NADH. Then the energy releasing phase will generate four molecules of ATP and the final two pyruvate molecules that are the products of glycolysis. There are 10 steps of glycolysis each is catalyzed by a distinct enzyme. The first step of glycolysis catalyzed by hexokinase is the phosphorylation of glucose to form glucose 6-phosphate. The phosphate group that's transferred onto glucose comes from ATP and so one ATP is used by hexokinase to produce glucose 6-phosphate and an ADP is another product of this chemical reaction. The second step of glycolysis is an isomerization reaction that converts glucose 6-phosphate to fructose 6-phosphate catalyzed by phosphoglucose isomerase. The third step is another phosphorylation reaction that converts fructose 6-phosphate to fructose 1-6 bisphosphate. This is catalyzed by phosphofructokinase and consumes another ATP molecule. The fourth step of glycolysis converts fructose 1-6 bisphosphate which is a 6-carbon molecule into dihydroxyacetone phosphate and glyceraldehyde 3-phosphate which are both 3-carbon molecules. Fructose bisphosphate aldolase is the enzyme that catalyzes this reaction. Then in the fifth step of glycolysis triose phosphate isomerase converts dihydroxyacetone phosphate to glyceraldehyde 3-phosphate. The sixth step of glycolysis is the end of the energy consuming phase and the beginning of when we'll start to produce high energy molecules that are harvesting the energy from the breakdown of glucose. Glyceraldehyde 3-phosphate is oxidized by glyceraldehyde 3-phosphate dehydrogenase to produce 1-3 bisphosphoglycerate. The electrons that are transferred from glyceraldehyde 3-phosphate are accepted by NAD+, producing a molecule of NADH, a high energy electron carrier. Because two molecules of glyceraldehyde 3-phosphate are generated from each glucose molecule, the sixth step, seventh step, eighth step, ninth step, and tenth step of glycolysis will occur twice for every glucose molecule that enters glycolysis. Therefore, two NADH molecules are produced as glucose is broken down by glycolysis. The seventh step of glycolysis, catalyzed by phosphoglycerate kinase, transfers a phosphate group from 1-3 bisphosphoglycerate onto ADP to form our first ATP molecule. Since two molecules of 1-3 bisphosphoglycerate are produced for every glucose, this reaction will be carried out twice per glucose molecule, generating two ATPs at this step, which will cancel out the two ATPs consumed in the first and third steps of glycolysis. The eighth step of glycolysis converts three phosphoglycerate to two phosphoglycerate. This is an isomerization reaction catalyzed by phosphoglycerate mutase. The ninth step of glycolysis is catalyzed by the enzyme enolase and converts two phosphoglycerate to phosphoenolpyruvate and water. The final step of glycolysis is catalyzed by pyruvate kinase and transfers a phosphate group from phosphoenolpyruvate onto ADP, forming ATP and the final product, pyruvate. This reaction will occur twice for every glucose that enters glycolysis, so we will have a net of two ATP produced at the end of glycolysis, in addition to two NADH molecules and two pyruvate molecules. To summarize the overall results of glycolysis, one molecule of glucose is converted to two molecules of pyruvate. In the energy-consuming phase, we lost two ATP, and in the energy-releasing phase, we gained four ATP. So a total of two ADP and inorganic phosphates were converted to two ATP molecules. We also generated two molecules of NADH during the coupling of phosphorylation with oxidation, step that is catalyzed by glyceraldehyde 3-phosphate dehydrogenase.