 Welcome back to the NPTEL lecture series on animal physiology. So, we finished with the gastrointestinal physiology and now we will be moving on to metabolism and thermoregulation. So, this is section 13 and there are dedicated two lectures for that. So, what we will essentially do in this section? So, as of now we studied when we take the food, we chew it up. The first set of reactions is start by the salivary gland. Then the food passes through the isophagus kind of a tunnel and goes to the stomach in an acidic environment. There it is exposed to hydrochloric acid and from there it moves on to small intestine. There is significant amount of absorption takes place and then to the large intestine likewise it gets rejected. During this process, we have appreciated how pancreas secretes different exocrine secretion and endocrine secretion. Secretion of insulin and vulcagon, we talked about the secretion from the liver, the bile juices, how they help in emulsification of the fats and everything. So, as of now we talked about in terms of the anatomical features and the movement of food through this anatomical structure. What we will essentially do now is we will give it a biochemical layer. So, what does that mean is? So, food basically consists of five different components. So, one of the major component is water, carbohydrates, lipids, proteins, some minerals which eventually form the electrolyte in our body and some vitamins and some hormones which are needed in very very low concentration and a series of minerals. So, these are absorbed, first of all these are degraded in through series of reactions. So, what we will do? First of all we will talk about or we will classify the different enzymes which are involved in breaking down of carbohydrate which is one of the major component of food, the lipids and the proteins. Once we talk about those, then we will talk about two or three different cycles by which these enzymes are involved in two distinct processes of metabolism. So, metabolism this word could be divided into two parts or the addition of two words could be considered metabolism. So, one is catabolism, the other one is anabolism. Catabolism is a process when there is a breakage of a bigger molecule into smaller pieces through enzyme mimetic action. Whereas, the reverse process when the smaller molecules added up to make a bigger molecule say for example, small peptides making a polypeptide chain or small single carbohydrate sugar molecules making a starch molecule or glycogen molecule that is a constructive process or where they that involves the integration of smaller molecules and that process is called anabolism. Both anabolism and catabolism are regulated by a series of enzymes. So, so start up with what I will do I will enumerate the different enzymes which plays significant role in our digest in the digestion of the three different chemical components. So, coming back to the slides. So, we are in essentially into section 13. Metabolism and third metabolism and temperature regulation. This is the second part of this. So, today we will be dealing with metabolism which is our lecture one. So, coming to the different components of the food we talked about to divide food in terms of chemicals chemical origin. So, then we carb lipids and proteins and if I classify the different enzymes which are involved in it for the carbohydrates you have martase taking care of maltose sugar sucrose breaking down the sucrose sugar lactase breaking the milk sugar or the lactose. Then you have secretion from pancreas pancreatic amylase or alpha amylase you have salivary amylase taking place from the saliva. Then from there let us move on to the enzymes which are involved in breakage of proteins. So, most of them are called proteases. So, proteases includes carboxypeptidase you have chymotrepsin you have dipeptidase peptidase. So, breaking down the peptide bond dipeptidase you have enterocoinase elastase, then you have pepsin then you have renin then you have trypsin these are some of the major ones and then coming to lipids they are mostly falling under the title of lipases which includes lingual lipase and you have pancreatic lipase. And then you have in that section a smaller section you can add which are called nucleases which includes mostly pancreatic nucleases. So, coming back. So, I have enumerated the list of different lipases different proteases different carbohydrate breaking enzymes and the nucleases. So, these are secreted by different parts of the digestive system or different part of the body. So, what I will do now I will highlight which part of the digestive system is some of them are self explanatory it is a pancreatic lipase means it is secreted by the pancreas, but there are others which are secreted by multiple organs of the digestive tract. So, we will just enumerate them. So, we put them in different color that makes more sense. So, coming to the mortises. So, mortises are secreted by small intestine I am just putting s i means small intestine sucre small intestine again lactase small intestine pancreatic lipase as it says that is by the pancreas salivary amylase it is by the salivar the among the lipases lingual lipase. So, lingual lipase is basically the glands of tongue basically all the way in the mouth to you in once then you have pancreatic lipases basically with pancreas nucleases by the pancreatic pancreas and among the proteases. So, carboxypeptidases by the pancreas then you have chymotrupsin by the pancreas and then you have dipeptidases that is by the small intestine then you have enterokinase by the brush water and the lumen of the small intestine s i then you have elastases are secreted by the pancreas dipeptidases by the small intestine then you have the renin which is secreted by the stomach and you have trypsin which is again by the pancreas and then you have the pepsin which is secreted by the chief cells of the stomach. So, and yeah so coming back so if you look at it so all these different enzymes are secreted by the different parts of the digestive system and in that whole process there is a division of labor. So, once it goes to the mouth it is chewed up by the teeth and these couple of enzymes are secreted either from the salivary gland or from along the mouth during in the oral cavity there are secretion and the food moves then there are renin and few other stomach enzymes are secreted from there in the intestine. But if you see the huge chunk of this concentration of these enzymes are concentrated along this in the small intestine and around the pancreas. So, this is the zone where most of them are concentrated along the small intestine and the pancreas. So, from here what we will do after giving you this overview of these different enzymes which are getting secreted we will move on to the different catabolism processes and the anabolism processes which are involved in the whole process. So, before we do so I will just take one step back. So, I talked about all this and all these different kind of enzymes in the slide. We will devote one more slide talking about all the different products of carbohydrates fats and proteins how their smaller components are getting absorbed and which part of the digestive system they are getting absorbed. Once we do that then we will move on to the catabolism and anabolism the different cycles which are involved the crypt cycle the icolosis gluconeogenesis and all those processes which are regulating the different aspects of metabolism within our body. So, coming back to the slide now. So, what we will do essentially at this point we will talk about who is absorbed where. So, we talked about all the components the carb we have lipids and we have the proteins. So, what is happening in the oral cavity in the oral cavity here you have the salivary amylase. So, from here it is getting broken down then. So, let us write down on the other side esophagus then you have the stomach I am just putting the initials small intestine and then you have intestinal mucosa and then you have the blood stream where the major absorption is taking place. So, during this course of movement of the food what is getting affected where. So, in the oral cavity it is basically salivary amylase from here it moves all the way to the small intestine in the small intestine it is basically one second I am just putting it slightly wrong. Let me put some lines that way it will be easy to you know break it down what is happening where fine now it is fine. So, the carbohydrate is moving all the way to small intestine after getting broken down into by the action of saliva amylase. So, here you have the pancreatic amylase which comes into play pancreatic alpha amylase and this pancreatic alpha amylase break down it into disaccharides and monosaccharides and from here these are absorbed by the intestinal mucosa. So, these are the intestinal mucosa where it is getting absorbed. So, basically these different component monosaccharides and disaccharides through facilitated diffusion and co-transport diffusion and co-transport and to further diffusion moves into the capillaries they are all in the form of monosaccharides. So, this is how the carbohydrate is being absorbed. So, initially it chew the food saliva amylase acts on it then the food is kind of partially broken down the carbohydrate part then those partially broken down carbohydrate moves on to the small intestine in the small intestine it receives secretion from the pancreas. So, the pancreatic alpha amylase helps in breaking it down into the monosaccharide and the disaccharides and then these disaccharides and monosaccharides are absorbed by the diffusion or facilitated diffusion or co-transport into the mucosa intestinal mucosa from intestinal mucosa they are transported to the blood stream. So, this is the fate of the carbohydrates. So, let us talk about the fate of the lipids what is happening to the lipid molecules. So, lipid molecules out here are under the action of lingual lipase we talked about this. So, from lingual lipase when it moves into the small intestine where the bile salts play a key role in emulsifying bile salt and pancreatic lipase these two play very critical role forming monosaccharide fatty acids in micelles monosaccharide fatty acid micelles. So, these micelles then diffused inside the intestinal mucosa and they form triglyceride then they form chylomicron and these chylomicrons are then moved via exocytosis. So, here basically exocytosis is taking place and they move on to the blood stream excuse me blood stream and the lactial glands. So, this is a synphilic is the fate of the carbohydrate which is sorry fate of the lipids which is moving through the from the mouth all the way to the intestine where by the action of the bile acids are getting emulsified and broken down into the into the glyceride monoglyceride and then it from triglyceride from the triglycerides it through the chylomicrons and now everything it is getting exocytosed and then it moves into the blood vessels and travel through the specific organs wherever it has to do expansion. So, from here we will talk about the fate of the carbohydrates which we have not talked yet. So, sorry the proteins so the proteins once their first action takes place in the stomach where basically your pepsin comes into play. So, protein become polypeptide next action from here they move on to the small intestine where there are series of enzymes which are involved in chymotrypsin elastase carboxypeptidase elastase carboxypeptidase. So, that from the short amino acids from there it diffuses into the intestinal mucosa in the intestinal mucosa. So, mostly this is facilitated diffusion in cotransport just like the carbohydrate facilitated diffusion and cotransport. So, here there are two different enzymes comes into play exopeptidase and dipeptidase and from here it moves on to the blood vessels. So, essentially in that whole process what is happening is the huge protein molecule is getting broken down into smaller amino acids this amino acids through diffusion and cotransport processes are absorbed. So, one absorption which I have not talked as of now I will talk about carbohydrate lipids and fats is how the different ions are getting absorbed what are the different processes. So, what we will do I will talk about the different ionic electrolytes I will just give you an enumeration I will enumerate the list of the different ions which are involved and how they are transported across the body and from there we will move on to the catabolism and the anabolism process. So, let us enumerate the different ions which are involved in it in our body. So, essentially we have sodium calcium like I am only talking about the major ones potassium magnesium iron chloride iodine S O 3 minus N O 3 minus P O 4 3 minus S O 4 2 minus and you have certain after this list you have water soluble vitamins and fat soluble vitamins. So, which includes A D E and K B and C. So, most of these are absorbed through the intestinal mucosa by process of either active transport. So, mostly there will be either active transport or diffusion and sometime carrier mediated diffusion and they are also absorbed not only in the intestinal mucosa these are also absorbed along the kidney as we have discussed in the kidney there along those along the nephron there are different zones where some of these are getting retained by the body and that is what help in the electrolyte regulation within our body. So, from here what we will do we will move on to the overall metabolic like overall layout of the catabolism and anabolism to give you an idea. We have talked about the enzymes we have talked about where these enzymes along the digestive tract are involved in the breaking down of the food components. We talked about have enumerated the different ions and the vitamins which are being used up by used by the body for different metabolic processes and how they are and transported across the lumen into different parts of the body where they will be needed for further anabolic action or catabolic action. So, now we will move on to the overall layout of the catabolism and the anabolism process. So, let us get back to the overall classification of anabolism and catabolism basically this falls under the A of cellular metabolism. So, cellular metabolism could be divided like this we have these organic molecules which includes your amino acids carb and lipids these organic molecule either via we have seen diffusion or transport they are all these two major modes they entered into the nutrient pool of the cell. Here there are two possibilities involved in anabolism. So, where basically you are synthesizing this is the part of the cell synthesizing new molecules or they are involved in catabolism. So, what is essentially happening in catabolism they are involved in different kind of breakage processes and which generates heat and similarly during this catabolism processes ATP is produced this ATP helps in the synthesis of different kind of these anabolic processes as well as other aspects like in a movement cellular movement in terms of mitosis when there is a movement of the different kind of cell organelles and the chromosomes which are moving the transport because transport needs enormous amount of ATP molecules and co-transport ATP dependent transport movement of the muscle there are several zones where that ATP which is produced as a part of coming back to the slide ATP which is produced at part of the catabolism process is being used. This is overall geometry if I had to tell you that how this all these things are happening. So, this is how this whole process is running and talking about the metabolic turnover and cellular ATP production T O I am just putting a short form of the turnover and cellular ATP production. So, essentially what is happening is that during. So, I am representing anabolism and A the anabolism the two possibilities either this anabolic product are secreted by the cell this is the cell or they are stored or these anabolic products have multiple roles. So, this could be broken down and helps in the different physiological function of course, for that you need the energy rich molecules ATP's which are of produced by the mitochondria and this anabolism anabolic products are helping growth and maintenance. These growth and maintenance eventually these to a lot of catabolism processes which enhance the nutrient pool of the body and this nutrient pool is again used up by the growth and maintenance and there is continuous supply in the form of food which are amino acids triglycerides and sugar which are coming into play. So, and if you look at the nutrient used in cellular metabolism. So, it is something like this here the mitochondria so where the TCA cycle is taking place come to that which is producing carbon dioxide and in that process out here you have the ATP production and using electron transport chain you have this small carbons like you know from glucose amino acids are all involved here fatty acids you have this triglyceride glucose are coming from glycogen and then you have xamina acids coming from the protein. So, this is your essentially the nutrient pool of the cell and this is essentially the storage pool. So, whenever the individual cell always have two phases of storing one will be the nutrient pool which is readily available like they are broken down in small pieces they are readily available for energy production and there is another pool which is the storage pool where you have the bigger molecules which are sitting there. So, those bigger molecules when they are breaking down into smaller nutrient pool they follow the catabolic route and then again those molecules are being utilized for energy production and simultaneously in order to have those storage molecule you have to go through the whole anabolism process. So, this is the overall kind of layout of the metabolic events at the cellular level from here we will move on to the three specific zones we will just browse through it about carbohydrate metabolism lipid metabolism and protein metabolism. So, this is moving on to the carbohydrate metabolism carbohydrate metabolism carbohydrate metabolism and to get the basic reaction is glucose plus oxygen leading to carbon dioxide and water formation. So, this is your glucose here you have the water. So, this is the basic basic most fundamental reaction of carbohydrate metabolism. So, the carbohydrate metabolism is or the formation of glucose molecule in this whole process the utilization of the glucose molecules. So, these are the most I should say most fundamental energetic bio energetic processes in our body. So, in this section we will talk about the glycolysis crepe cycle and how all these processes are intertwined in the gluconeogenesis processes and in the building of processes. So, coming back the glycolysis process is happening. So, the first the word which comes here will be glycolysis. So, whenever you see any word called lysis means breaking down breaking it down into. So, basically what is happening is that glucose is broken down into pyruvic acid this is basically what we meant by glycolysis process and what it requires there are certain basic requirements first one is glucose molecules first one the second one is cytoplasmic enzyme third one is ATP and ADP fourth one you need inorganic phosphate and I need NAD and NADH so nicotinamide adenine dinucleotide. So, NAD stands for dinamide adenine dinucleotide. So, these are the five major things what is needed for the glycolysis process. So, what are the steps in glycolysis? So, as we already talked about. So, this is happening inside the cell. So, let me demarcate it like this. So, this is the green line what you see is inside the cell. So, the glucose is coming inside the cell. So, here is you have the glucose from glucose is converted into glucose 6-phosphate glucose 6-phosphate and that in that process there is an ATP to ADP conversion. So, that needs energy sorry ATP forming ATP and there is a lot of energy which is needed in that process from glucose 6-phosphate it forms fructose 1, 6 bisphosphate. This step is also energy requirement processes ATP to ADP adenosine triphosphate to adenosine triphosphate. At this stage there are two phase possibly two phase one is glyceroldehyde 3-phosphate or it could form dihydroxy adenine. So, acetonphosphate. So, dihydroxy acetonphosphate can again transform into glyceroldehyde 3-phosphate and from here the acetonphosphate forms 1, 3 bisphosphoglyceric acid acid and from there and at this stage from 1, 3 bisphosphoglyceric acid to phosphoglyceric acid there are two ADP molecules transformed into two ATP molecule. For the first time the reverse process is taking place in this cycle and from here it get rid of water molecules and then it form something called PEP phosphoenol pyruvate. And from phosphoenol pyruvate it forms pyruvic acid and this during this formation again two ADP molecule is utilized to make two ATP molecules. So, if you look at this process at this two zones out here and out here you have developed ATP molecules whereas, here you have consumed this is basically you have broken down ATP molecule and here you have made ATP molecule. And if you look at the energy summary in terms of the ATP. So, there are minus 2 ATP and here you have plus 4 ATP and essential gain is plus 4 minus 2 is plus 2 ATP in this whole process and here it is I will highlight one thing. So, you saw this reaction I will do it so easily, but think of it anybody can draw that reaction, but how many enzymes are involved in it. So, at every step of this reaction from glucose to glucose 6 phosphate, bisphosphate, phosphoenol pyruvate, pyruvic acid all these are regulated by enzymes. So, as of now we only talked about the enzymes which are involved in breaking down of the carbohydrate amylase, alpha amylase, pancreatic alpha amylase, salivary alpha amylase, lactase, galactase, so on and so forth. But, they are just a big chunk of carbohydrate which you are breaking down into small pieces, but then that individual glucose molecule is going through from glucose to pyruvic acid what I just now drew for you. You must have observed that how like how many reactions are involved in that and each one of these reactions are regulated by an specific enzyme. Without that this process would not happen. So, that is the reason that the cellular metabolism needs all those different enzymes at one point of time other than the enzymes what we have already enumerated. And we have seen this whole glucose breakdown process to pyruvic acid finally, lead to the formation of two energy rich molecule. So, every molecule of glucose at the end produce two energy rich ATP molecule that is essentially is the take home message from this process what is happening in the breaking down process of glucose. So, it is a catabolic process by the way and this catabolic process where glucose is further. So, first series of catabolic process is like this. So, if I had to put, so you have this huge carbohydrate molecule then this forms small say glucose small molecule. So, this is the catabolism I am just representing with the pink c. So, there is a catabolism process from here it forms pyruvic acid. So, this is another catabolism process and this is another catabolism processes. And during this whole catabolism processes it leads to formation of ATP. So, each one of each one of this molecule lead to the formation of an ATP molecule two ATP molecule. So, this is very essential and just once they are forming pyruvic acid it is not end of the story that pyruvic acid went inside the mitochondria and leads to a cycle called TCA cycle tricarboxylic acid cycle that tricarboxylic acid cycle is fed into the electron transport chain of the mitochondria and there it plays another set of reactions for the anabolic and the catabolic processes. So, what we will do today we will go through the tricarboxylic acid cycle of that pyruvic acid which has formed coming back to the once again. So, now you have the pyruvic acid out here pyruvic acid this pyruvic acid through quinzyme A process utilizing an NADH out here become acetyl CoA with acetyl CoA form citric acid then it form a 5 carbon structure and then it form a 4 carbon structure then that 4 carbon structure in that process eventually become acetyl quinzyme and this is all happening out here inside the mitochondria. And out here what is essentially happening during this process is that there are this keep on looking I am just. So, this is generating ATP out here there is always a proton gradient which is getting created in this process and carbon citric acid 6 carbon. So, this is basically 6 carbon gives away a CO 2 out here and 5 carbon it is giving out a CO 2 out here. And these proton gradients which are getting generated out here to H to H these are different proton gradients. So, these all these proton gradients along here along here are being picked up by this different FADH to NADH they are. So, you have the other out here to NADH. So, to here also NADH and all these become part of the electron transport chain of the mitochondria. So, they are involved in the electron transport chain and this is one of the most key reaction TCS cycle which is called. So, this is one of the most key reaction of the body which is involved in feeding the electron transport chain and formation of the ATP molecule. So, what is happening what is the fate of these different NAD and NADH system is inside the mitochondria is. So, these NADs through a series of reaction. So, basically this whole electron transport chain is going is at different gradient going through cytochromoxidase, cytochrome B, cytochrome C, cytochrome A, cytochrome A 3 likewise all these different reaction processes and different donors of the electron along this whole process inside the mitochondria is leading to the formation of final in product of this whole game is ATP production. So, so this is some of these things which I have not already discussed. So, this is FMN is basically flaben nucleotide and these are the coenzyme A coenzyme Q coenzyme A and different other factors which are involved in this whole process. So, if you look at it. So, we started in outside the cell when the glucose moieties started coming in glucose moieties got transformed and from that point onward through the formation of glucose to pyruvic acid and then this pyruvic acid gets inside the mitochondria and through acetyl coenzyme A formation and everything leads to a proton gradient and this proton gradient is eventually involved in the production of the ATP molecules out there and this proton gradient which is created along the mitochondrial membrane is one of the critical aspect of bio energetics which is kind of the lifeline at this thing some of these reactions are the bio energetics basis of the life form on the floor of earth. So, in that process what we will do now will summarize the whole process in terms of the ATP production before we move on to the lipid and the protein metabolism. So, talking about the summarizing this whole process in terms of the lipid production in terms of the ATP production. So, this is what is essentially happening. So, during glycolysis you have 4 ATP and minus 2 ATP is being used and what you get is 2 ATP now at the electron transport chain now we are entering into the electron transport chain. So, you have 4 ATP then you have 24 ATP in the TCA cycle and you have another 4 ATP which is formed different stages of the cycle another 2 ATP which is formed and some total of the cell during this whole net gain of the cell from aerobic catabolism from one glucose molecule what we essentially get is 36 ATP molecule. And how that happens we are going to come now I will draw the chart to show you how this whole thing is happening. So, you have glucose you have 2 ATP forming 2 ADP. So, you are utilizing 80 P's now and you have 4 ADP forming 4 ATP. So, this is the first set of reaction which leads to plus 2 ATP formation from glucose 6 carbon to pyruvic acid now pyruvic acid is entering inside the mitochondria inside the mitochondria pyruvic acid goes through to form acetyl CoA and acetyl CoA in enter inside the TCA cycle. And during that process it forms from pyruvic acid to acetyl CoA it is forming NADH these NADH through the electron transport chain. So, there are 2 NADH here and there are 6 NADH and there are 2 FADH 2 which are all outcome of the tricarboxylic acid cycle. So, this and via and there are few there is one more source by which it comes. So, during formation of glucose to pyruvic acid there is another just show it you in another color so that there is an NAD molecule which is formed which is fed from here from outside this NAD molecules also become part of the electron transport chain. So, if you look at it so there are 2 NAD is 2 NADH molecule which are coming in from here there is there is another 2 which is coming from here. So, let me highlight them so 2 coming from here 2 coming from here 2 plus 2 4 and you have 6 NAD is coming from fed from here 2 FADH to fed from here and in that process what is happening here. So, this is leading to the formation of 4 ATP out here 2 NAD is again leading to the formation of 4 2. So, 2 is leading to the 4 this 2 is leading to another 4 this 6 is leading to 12 and you have 2 FADH to molecule which is leading to formation of 4. So, if you add up this 4 12 plus 4 6 4 4 8 8 4 12 12 12 24 and you are making 26. So, essentially what is happening is that you have 2 2 NADH 6 NADH 2 FADH 2 ok 2 FADH 2 and. So, 2 NAD NADH and 6 NADH is leading to the formation of actually 2. So, basically out here just out here you are making 24 ATP molecule and there is 2 more which is coming from a GTP and GTP and this eventually leads to 4 ATP here 24 ATP here you have 4 ATP here and another 2 coming from the tricarboxylic acid cycle and what you essentially get is that 2 plus 4 plus 24 plus 4 plus 2 4 plus 2 6 6 10 14 14 16 plus 3 36. So, this is basically what is happening in the process of ATP production there are 36 ATP molecules which are generated from a single glucose molecule when it goes through the whole process of pyruvic acid formation and tricarbox and through the tricarboxylic acid cycle. So, what we will do next is that in the next class I will goes in here in the next class we will move on to in the gluconeogenesis process lipid metabolism and protein metabolism and thermal regulation thanks a lot.