 Dear students, today we are going to deal with a tent metabolic pathway related to carbohydrates. We all know that carbohydrates are considered as the principle source of energy of the body. Of these carbohydrates, one important monosacrate is the glucose is considered as the preferred source of energy for most of the body to choose. Say for example, brain cells, they derive the energy mainly from this glucose. So whenever the glucose metabolism is deranged in our body that can lead to life threatening conditions. So there is always a mechanism in the body in order to maintain the blood glucose level at a constant level. When the blood glucose level is increased, we call that condition as hyperglycemia. When it is decreased, we call it as hyperglycemia. So in order to maintain this glucose level at a constant rate, there are certain metabolic pathways that is operating inside the body to keep it at a balanced level. The normal blood glucose is kept in a reference range of around 70 to 110 milligrams per deciliter. When it goes at a high level, the body can't tolerate. Similarly, when it goes to a decreased level, there also the body can't tolerate. So for a proper day to day function of our body, the glucose level always each be kept at a balanced level. So the balanced level is because of the proper operation of all the metabolic pathways that is present within the body itself. So today we will see an important pathway related to this glucose metabolism and that pathway is glycolysis. This pathway is also called as Empton May of Pathway. The name glycolysis, it has been derived from a three quote. It means that it is a splitting of the sweet. Here the sweet is glucose. So the glucose is laced or the glucose is split. So what happens is glucose in the end, in aerobic conditions, this glucose is converted to pyruvate and in aerobic conditions, this is the expected glucose it is converted to lactate. And another important peculiarity is that all the reaction steps of this glycolysis, it happens or takes place in the cytoplasm. And it is the only pathway that is taking place in all cells of the body. And this is the only source of energy for erythrocytes. So this diagram, it represents that the process of this glycolysis occurs in the cytoplasm in eukaryotic cells. Similarly also in prokaryotic cells. So here you look what happens to this glucose. Glucose by means of this aerobic oxidation, the end product of this glucose is pyruvate. Here this is the glucose molecule which is a 6-carbon molecule. At the end of this reaction it is converted to a 3-carbon compound that is pyruvate. This picture, it represents the overall steps of this glycolysis. Here you can see the major enzymes that are involved in the conversion of this glucose to pyruvate. And step by step you can see the intermediate products that are produced by means of these reactions. And the end you can see the compound pyruvate. This is the case of this aerobic oxidation. But in anaerobic condition this pyruvate it will be converted to lactate. So we can say that the glucose is converted to pyruvate by means of aerobic oxidation. And this glucose is converted to lactate by anaerobic oxidation. So now step by step we will see what happens to this glucose. So this is the first step of glycolytic pathway. That is the conversion of this glucose to glucose exposimate. Here you can see the enzyme involved is exokinase. So kinase, this respective enzyme it is involved in the transfer of phosphate through. From this ATP molecule to this glucose. So that this glucose is converted to glucose exposimate. And ATP after donating its phosphate group it changes to AD. ATP is converted to ADP the same time glucose by utilizing one of the phosphate group of ATP is converted to glucose exposimate. And here the enzyme that is involved in this step it is exokinase. So coming to the next step what happens to this glucose exposimate that has been generated from this glucose. This glucose exposimate by means of an isomerization reaction catalyzed by an isomerase. It is converted to fructose exposimate. And isomerase is phosphor glucose isomerase or phosphofixose isomerase. Here if you observe the respective structures you can see that there is no major changes that has been happened. But only isomerization. That means the molecular formula it remains the same but there has been some structural difference. So phosphor glucose isomerase converts this glucose exposimate to fructose exposimate. So that's the second step. Now the third step of this glycolysis. Here the fructose exposimate which is further phosphorylated. So the phosphorylation it is carried out by a kinase. Here we can call this kinase as phosphofructose kinase. So it is said to be an important enzyme in the glycolytic pathway. So just have a look into the fructose exposimate which is only having one phosphate group in its structure. Now by the addition of another phosphate group which has been donated by one molecule of this ATP. This fructose exposimate is converted to fructose 1,6 exposimate. So just have a look into the previous slides. Here the first step when the glucose is converted to glucose exposimate. This reaction is said to be an irreversible reaction. Coming to the second step. Here you can see that this is a reversible reaction. It can be converted to fructose exposimate. It can be converted back to glucose exposimate. The third step you can see here. This is also a irreversible step. Now coming to the fourth step. The fourth step we are closely observing. Here you can see the difference. The produced fructose 1,6 phosphate by means of the third step is converted to glyceraldehyde 3-phosphate and also dihydroxyacetone phosphate. Firstly in the fourth step fructose 6-phosphate is converted to dihydroxyacetone phosphate. And at the same time glyceraldehyde 3-phosphate is also generated. The reaction it is catalyzed by an enzyme called as alkylase. Fructose 1,6-phosphate is converted to one molecule of glyceraldehyde 3-phosphate and also one molecule of dihydroxyacetone phosphate. At the same time this dihydroxyacetone phosphate is isomerized to glyceraldehyde 3-phosphate. By the enzyme phosphotriose isomerase. Phosphotriose isomerase or it is also given as triose phosphate isomerase. The net result is that the glucose molecule is now cleaved into two molecules of glyceraldehyde 3-phosphate. One from fructose 1,6-phosphate and another through its conversion from dihydroxyacetone phosphate. So two molecules of this glyceraldehyde 3-phosphate is produced. Now the next step the glyceraldehyde 3-phosphate which has been produced in the earliest step it is dehydrogenated. And at the same time it is simultaneously phosphorylated to produce 1,3-bisphosphoglycerate to produce 1,3-bisphosphoglycerate with the help of NAD. This is a reversible reaction. In the next step the produced 1,3-bisphosphoglycerate from the earliest step it is converted to 3-phosphoglycerate. Here a kinase enzyme is involved. Here what does this kinase do? This kinase it accepts the one of the phosphoryl residues or phosphate groups of this 1,3-bisphosphoglycerate. It transfers or it converts its ADP to ATP. At the same time this 1,3-bisphosphoglycerate is converted to 3-phosphoglycerate. Now it has only one phosphate group in its structure. Previously there were two phosphate groups and it was called as 1,3-bisphosphoglycerate. Now we can call it as 3-phosphoglycerate because the phosphate group that was present in the first carboxylase residue has been now accepted by ADP and by the ADP is converted to ATP. And the 1,3-bisphosphoglycerate molecule is converted to 3-phosphoglycerate. Now coming to the next step. Here this step is catalyzed by an enzyme called as a mutase. More precisely we can say it as phosphoglycerate mutase. The only difference is that there is a structural rearrangement in the structure. The phosphoglycerate molecule is converted to 2-phosphoglycerate. The phosphate group which has been present at the third position which is now it has been shifted to the second position in the presence of the enzyme phosphoglyceramutase. This is also a readily reversible reaction. In the next step the 2-phosphoglycerate is converted to phosphoenolpyrate by the enzyme enolase. Similarly at the same time there is the removal of water molecule. The reaction is said to be a reversible one. And this enolase, this respective enzyme in most cases or it requires magnesium ions for catalyzing exactly. In the next step the phosphoenolpyrate is dephosphorylated to pyrate. Dephosphorylation means it is the removal of this phosphate group or the removal of this phosphoryl residues. So if you are simply observing the structure you can see there was a phosphate group in the earlier structure of this phosphoenolpyrate. And when it gets converted to pyruvate the phosphate group has been formed. So another peculiarity is that this pyruvate kinase is also considered as a key glycolytic enzyme. You can see this is the enzyme and this reaction is also a reversible reaction. And what happens to this pyruvate? This pyruvate anaerobic oxidation is happening. This pyruvate it gets converted to lactate. The pyruvate will be converted to lactate. The pyruvate it is reduced to lactate by the enzyme lactate dehydrogenase. But in normal cases we can say that the end product it is the pyruvate enzyme. But in anaerobic conditions this respective pyruvate will be converted to lactate in the presence of the enzyme lactate dehydrogenase.