Glycolysis biochemistry

[Music] welcome back friends welcome to another video tutorial from somos biology and in this series of videos we are going to talk about carbohydrate metabolism and especially we want to talk about the cellular respiration so we will look at the different stages of cellular respiration and what they are made up with so if you think of cellular respiration of carbohydrate metabolism it starts with a process known as glycolysis and then the process goes like the modification of pyruvate into acetyl quai that is done by pyruvate dehydrogenase complex then the third stage of the process is known as the Krebs cycle and the fourth stage of the process is known as the electron transport chain to generate energy so now if you look at the overview of complete process of cellular respiration it always begins with glycolysis in this first video we want to talk about the first stage of this cellular respiration that is glycolysis the idea of cellular respiration is simple that we eat food and the part and fragments of that food after the digestion reaches to our cell and inside the cell all those food particles are broken down into the macromolecules that is carbohydrate lipid proteins these are the three major macromolecules that they produced after the food digestion and little bit of nucleic acids as well now what we do is all those fragments that we are talking about that is that is carbohydrates lipids and proteins all these materials are then taken inside the cell and start breaking down they start broken down and produce energy because these molecules contained energy because they are produced by the plants or producers with the help of a process known photosynthesis so they produce this food we take this food you break them down and then we utilize the energy so the idea of cellular respiration is to utilize all those macromolecules to produce energy inside the cell and to make that they have different process of metabolic pathways numerous metabolic pathways force carbohydrates lipids and proteins they have separate metabolic pathways for the generation of energy from all these macromolecules now here we are talking about the process of carbohydrate metabolism especially and the carbohydrate metabolism if you see what happens is in carbohydrate metabolism it starts with glycolysis so glycolysis is a process where we usually take carbohydrate the simple form of carbohydrate let us take glucose and we convert it into pyruvate then the second stage of the process if we go then we take this pyruvate which is a let us take this pile of it as a substrate and convert it into acetyl co a ok and this step is known as an catalyzed by the pyruvate dehydrogenase complex then comes a third part of the third step of this respiration steps and that is Krebs cycle and what happens in Krebs cycle again the product of the early state which is acetyl co is taken as a substrate so you take acetyl co a as a substrate and they generate and they oxidize the oxidized as a takeaway and all the materials that is produced there at the end of the glycolysis stages and processes they oxidize it and they produce a lot of energy containing compounds like ATP in eight eh fadh2 now what happens all the stages are sequentially starting from glycolysis then pyruvate dehydrogenase complex and Krebs cycle after that after the Krebs cycle is done then what they take they take all those molecules like ATP nadh fadh2 they take all this things and they utilize the energy stored in ATP nadh and fadh2 to produce energy currency of the cell that is ATP because whenever a tip is directly produced it can be utilized then and there but molecules like nadh fadh2 their electron carriers so there is a tendency on our body using electron carriers as a donor of electrons and driving a set of processes to generate more molecules of ATP and that concludes the fourth stage of the cellular respiration and this fourth stage is electron transport system on electron transport chain and at the end of this electron transport chain what happens all these molecules that are produced they are utilized to produce more and more energy currency energy molecule that is ATP so this is the overview of cellular respiration in our body if you look all these stages now here in the sequential stages of series of videos we are going to talk about all this fragments about glycolysis about the conversion of pyruvate into acetyl-coa about Krebs cycle and about electron transport system and we will see their advantages and what they are required for their processes and all the detailed steps of each and every process that we've described till now so stay tuned and watch the video throughout because we are going to talk about all of them in details glycolysis is a process by which the body converts glucose into pyruvate now pyruvate is then either converted to lactate or lactic acid it which is an anaerobic process or it may also be converted to acetyl co a for use of that a cetera in another cycle known as citric acid cycle that ultimately leads to further conversion of that pyruvate and then finally through electron transport system it generates energy let's move now the process of glycolysis can be divided into three different parts the first part is known as the priming part where a priming step involves in the requirement of 2 ATP molecules the sugar splitting state is the second step of the glycolysis in this step one molecule of glucose becomes to three carbon molecule compounds as you can see here before the splitting we have fructose 1 6 bisphosphate in the splitting step that fructose 1 6 bisphosphate which is a 6 carbon molecule is divided into two 3-carbon molecule naming li glyceraldehyde-3-phosphate and dihydroxyacetone phosphate after that the third step or it's known as an energy extraction step in this tape the energy of the sugar is harvested in the form of ATP and NADH both of these molecules nadh and ATP are energetic molecules and two molecules of those ATP and one molecule of NADH are generated from one of those three carbon molecule that was generated earlier so the first step of priming consumes two ATP while the energy extraction steps provide us two ATP and NADH now let us look at each of the process in much more detail in biologically irreversible step is this first step and in this first step the glucose is phosphorylated into glucose 6-phosphate and this is the most important part of the step it is irreversible in nature and as it is in diversa belen nature the commitment for this step dictates the commitment for the cell to continue the glycolysis process so this is a rate determining step now the enzyme for this step is mainly gluco kinase gluco kinase can be present in liver and when the glucokinase enzyme is present in different parts of the body it is known as the hexokinase the liver is able to regulate the blood sugar level because of different differences in the km values between this gluco kindness and hexa kindness are in the different regions of our body okay and the uptake and regulation of this glucose also mediated by different glucose receptors that are present in different regions of our body cells now if you look at this process in details it comes simply addition of a phosphate group to the to the sugar or to the glucose from the beginning once it is added magnesium is required for this enzyme to function properly so magnesium act as a cofactor and the most important point that this is irreversible step and this is an energy consuming step and this is a commitment step for like Oh lysis so if this tape is done then obviously the cell is under growing the rest of the stages of glycolysis as well so there is no going back after this the second step of glycolysis it is reversible step and it sets of the molecule for cleavage between the three carbon and the four so if you look at here this is earlier if we talk about that the structure is modified from glucose 6-phosphate to fructose 6-phosphate and the enzyme involved is known as phosphoglucose isomerase which changes the structure of the glucose 6-phosphate into fructose so it changes the structure into an isomeric form that is known as isomerase enzyme okay and this conversion is actually a conversion from Aldo sugar to a keto sugar if you look at here glucose 6-phosphate is an aldol sugar that is converted to kiito's which is fructose 6-phosphate now the difference between aldoses and ketoses you can look at here the form is in aldoses hexameric ring in ketosis a pentameric ring now the third step of the reaction is also irreversible step and in this case it uses phosphofructokinase enzyme or pfk as a process of conversion of fructose 6-phosphate into fructose 1 6 bisphosphate and this is another step where there is a phosphate group transferred from ATP to the fructose 6-phosphate to convert it into fructose 1 6 bisphosphate ok so two phosphates group will be added and again for the addition it is another energy consuming step and they also require a cofactor magnesium now the key point is this step is irreversible it is also committed step at the major point of metabolic control and there is more than one type of phosphofructokinase inside our body which also makes a little bit different in the different parts of the phosphofructokinase activities we will talk about the phosphofructokinase activities later the fourth step is the splitting of the fructose and this is also energetically unfavorable but this process is driven and this is driven forward by the low concentration of the products if the product concentration is little high then this process will be blocked or this step will be blocked okay because as the products that are produced further continues to be removed by conversion that lower product presence helps them to properly convert fructose 1 6 bisphosphate into the 3/2 carbon to three carbon molecules so normally fructose 1 6 bisphosphate is also having 6 carbon they have two different phosphate groups attached now it is degraded it is broken and we produces two different three carbon compound instead and the three carbon compounds are glyceraldehyde-3-phosphate and dihydroxyacetone phosphate and the enzyme associated for this process is known as aldolase enzyme now the key point for this reaction that this is a very important step that that intersects with the fructose metabolism with the pentose phosphate pathway and the lipid metabolism as well so this is a very interesting branch point of the process of glycolysis and this is also a splitting step from six carbon two to three carbon molecules now if we go to the next step that is a conversion or inter conversion between the glyceraldehyde-3-phosphate and dihydroxyacetone phosphate glyceraldehyde 3-phosphate can be readily converted to dihydroxyacetone phosphate it is known as DHAP and this is also reversible reaction so that they can easily change between their structures inside the change is very easy to construct depending upon the structures if you look here is easy to achieve now the enzyme involved with this process is known as triosephosphate isomerase and the key points to remember is that this is tape is effectively doubles all the products that are shown here so once this glyceraldehyde 3-phosphate is a three carbon so whatever thing we'll see downstream of it will be produced from a three carbon molecule but we know actual molecule was six carbon so every of this process is that we are going to see further will be applicable for each of those three carbon intermediates glyceraldehyde-3-phosphate and dihydroxyacetone phosphate the next step of this reaction is the oxidation and that uses electron accepter that is very very important in the biochemistry and the role of electron acceptors which is nad plus and this is the step of converting ILD hi 3-phosphate into 1 3 bisphosphoglycerate and in this case of this transfer they transfers this energy or electron to any D once it's transferred the electron to energy and he also requires an amount of phosphate because the phosphate will be added there because we are converting literally 3 phosphate into 1 3 bisphosphoglycerate because the phosphate group is added to both 1 & 3 carbon positions there and the electron is transferred to nad to convert it into NADH + H+ which is the reduced form of nad now in this case the enzyme required for this process is glyceraldehyde-3-phosphate dehydrogenase not only this nicotinamide and flavin enzymes frequently shuttle electrons between the metabolic process like glycolysis and the mitochondrial electron transport chain however to be used in that way it must first be transported into the mitochondrial matrix so whatever electrons generated base NADH transfers them to the mitochondrial matrix and then they use that for the process of electron transport chain which will also study later now the letter step is the conversion of 1 3 bisphosphoglycerate into 3 phosphoglycerate now most ATP is produced by the electron transport chain in comparison go the kinase reaction is an example of what is known as substrate level ATP production ok so what happens in this case as we know that 1 3 bisphosphoglycerate has had two different phosphate groups now one of that phosphate group is cleaved and attached to the ADP now adp once attached to the phosphate group converted itself into ATP by this fashion the substrate is helping to produce ATP known as substrate level phosphorylation now unlike the other kindness in the glycolysis this is an example of readily reversible kinase activity and this activity helps to generate ATP for the first time in the of glycolysis the enzyme involved is phosphoglycerate kinase and the cofactor required this process like any of the kinase enzymes is also magnesium let us move to the next step in this particular step this 3-phosphoglycerate is now converted to 2-phosphoglycerate it's simply the rearrangement of the phosphate group from the carbon number 3 to 2 now 2 3 bisphosphoglycerate is an important mediator of this phosphate transfer it is formed from 1 3 bisphosphoglycerate it is also important in affecting the oxygen affinity in the hemoglobin in the blood which we'll also see in a separate video so in this case the enzyme involved for this process phosphoglycerate is not simply interchange the structure and the cofactor required as we told to 3 bisphosphoglycerate ok now once to phosphoglycerate is produced now that 2-phosphoglycerate can also be modified in the later stages and the 2-phosphoglycerate is modified in the phosphoenolpyruvate or PEP and in this case this is the this is the 2-phosphoglycerate this phosphate group remains it is and water molecule released once the hydrogen and hydroxyl hydroxyl released from the third carbon and the hydrogen is released from the bond between the second carbon that releases water out of it so dehydration step occurs which converts to phosphoglycerate into phosphoenolpyruvate and you know phosphoenolpyruvate is a very very energetic molecule it contains a phosphate and very less those it does not even have those hydrogen or hydroxyl content as the water is released so this is a very energetic molecule the enzyme involved in this process is known as enol is and this process is inhibited by chlorides so chloride are toxic and those any types of chlorides are actually toxic at this specific region or they block this specific part of the reaction of glycolysis the letter stage or the last step of the glycolysis is the use of enzyme known as pyruvate kinase which is a very large like in enzyme and this pyruvate kinase converts phosphoenolpyruvate into pyruvate and as I told you phosphoenolpyruvate is a very energetic molecule and it also contains a phosphate group so while conversion in from PEP to pyruvate they transfers this phosphate to ADP that makes ATP so we get the second round of ATP production in the glycolysis pathway now there is a very large negative free energy associated with this reaction it is biologically irreversible reaction it puts entire pathway towards the completion so this is one of the most vital stages of glycolysis of all now this step is also inhibited by different molecules it is inhibited by the presence of ATP because presence of ATP means presence of energy inside the cell if there is a lot of energy inside the cell cell will not want to produce more after glycolysis or Krebs cycle so ATP prevents tape so as alanine amino acid the liver also controls the step by covalently inhibiting the enzymes by phosphorylating this pyruvate kinase enzyme if you phosphorylate this enzyme it gets inactivated so by this fashion this the most important points of the step it is irreversible liver inhibits glycolysis with more sensitivity than other tissues or other regions of our body so this in a sense is the end now once the pyruvate is being made it is a product of glycolysis but there are some faith of the pyruvate now the faith determined by the presence of air or the absence of air now under aerobic conditions it is mostly converted to acetyl co a ok which will be shuffled between oxaloacetate and however in anaerobic condition it must be converted to lactate and once it is converted to Lac it it realizes NADH oxidize NADH to NAD+ and in that case they produce lactate and lactate can be an production of lactate from pyruvate can also be used to regenerate NAD+ now this is especially important in cells that rely exclusively on glycolysis for energy like red blood cells in that case these are the possibilities and the process of conversion of pyruvate into lactate is known as a lactic acid fermentation and the enzymes required for this is lactate dehydrogenase

Channel: Shomu's Biology

Views: 364,764

Keywords: suman bhattacharjee, shomus biology, glycolysis, atp, pyruvate, nadh, glucose, glycolysis biochemistry, regulation of glycolysis, glycolysis steps, glycolysis pathway, glycolysis regulation, cellular respiration, metabolic pathway, biochemistry, metabolism, carbohydrate metabolism, pathway of glycolysis

Id: PK8Lf7N5gIA

Length: 22min 49sec (1369 seconds)

Published: Fri Feb 03 2017