 Welcome back to the course on animal physiology, we are into the section 2 and today we will be getting into the third and the final lecture of the section 2, section 2 which consists of our membrane physiology of nerve and muscle. So, we have already finished first two lectures, now we will be heading for the final lecture on this physiology of nerve and muscle. So, section 2 lecture 3 of 3, there are 3 lectures which we dedicated for this section. So, we are done with first two, now today we are moving into the next lecture. So, we started with this broad heading of membrane structure and dynamics. So, we have talked widely about the structural part of the membrane, but we have not talked about the dynamics of it. Dynamics means the membrane is a very dynamic structure, there is continuous exchange of information from inside to outside the cell and this information transfer is rapidly carried out by the membrane. So, this whole dynamicity is governed by a wide range of transport phenomena that is what we will be discussing. Before I move on to the dynamics of it, there are couple of steps which I hurriedly crossed in the last lecture in the last almost after the fag end or the tail end of the last lecture, which is just want to reiterate its kind of a carry over from the previous lecture and then I will move on to the dynamics part of it. So, in the last lecture I was talking about the presence of the carbohydrates on top of the membrane. So, I told you there are two ways by which carbohydrate can bind the carbohydrate like this, if this is the membrane, if this is the membrane which has been shown by two lines and I am just putting the hatched this thing. So, one option is that the carbohydrate is directly attached the way it has been shown here on the lipid or there may be a protein like this. So, which is represented by like this protein and on top of the protein there is a carbohydrate which is attached. So, there are two motives by which a carbohydrate can attach on top of a membrane. Here is the carbohydrate and here is the lipid and this is inside the cell and this one is outside the cell. So, I highlighted one point, but as in a in a rush we just finished it that carbohydrates are present always on the outer surface. So, they face outside the cell what really carbohydrate does actually. One of the thing which carbohydrate does is it helps in cell to cell signaling and it helps in the identification of the different cell types. They are kind of you know your house has a house number then you have a name of the colony then you have the name of the city and on top of that there is a zip code or a pin code. So, that is how your letter reaches to a specific to your house same way a cell has such identification mark and those identification marks are in the form of carbohydrates which are present on the cell surface. So, these carbohydrate determines. So, all of you are aware of that we are having different kind of blood groups. So, we have like you know as you are aware of people have blood groups like A B A B and O these blood group is determined by those carbohydrates which are present on the surface. These are determined by the carbohydrates on cell surface. This is one of the major role and we will be discussing in depth what are the structure of these apart from it there are certain. So, how we study this carbohydrate. So, another broad heading how we study these carbohydrates which are present on the cell surface. So, one of the potent tool is a range of molecules called lectins. These are carbohydrate binding proteins carbohydrate binding proteins and some of these major proteins are con cannavalin A and there are some thing called with glutinine and all these kind of molecules which bind to these different carbohydrates and these are being used. So, these are the tools by which we study the carbohydrate molecules which are present on the cell surface and they have a profound role to play in different kind of physiological processes which are taking place and not only cell identification. They help in chemotaxis and the migration of the cell and several other phenomena which are exceptionally important for proper physiological functioning of the body apart from it another topic where I kind of ended up how we isolate the membrane proteins from the membrane using detergent we I talked about some of the detergents like you know how let me put the question how we use detergents in studying membrane proteins. So, some of the detergent examples of some of the detergents which I talked about in the last class was triton and few others. So, what they exactly do is that say for example, if this is the membrane and you have these membrane protein sitting here like this. So, if this is the membrane so let me give another shade. So, this is the green what you are saying is the lipid bilayer sorry the blue what you are saying is the lipid bilayer and this green are the membrane proteins which are spanning across the membrane. So, what we do is say for example, this red we add a detergent say for example, triton what the detergent does is something very interesting next come out depending on the concentration of the detergent to get out of is that you get this membrane protein shaded in green the way it is and on top of that you have a small layering of the lipids around it likewise. And once you have this particular membrane protein out of the surface though it is a exceptionally challenging process by the way here is the membrane protein at your for your further experiment. We reconstitute membrane protein. So, this is the membrane protein this is the membrane protein and this is the membrane and this is where you are adding the triton into it. And then we reconstitute the protein in lipid vesicles. This is the part which I wish to highlight in this. This is the carryover from the previous lecture where we just hurriedly close on because of time constraint in the last lecture. So, this was what was missing. So, this is the tail piece which I needed to add before I start with the membrane structure and dynamics. So, coming back to it. So, where we are supposed to use this start this lecture. So, membrane structure. So, we are done with the structural part. So, this part is done. Now, we are starting the dynamics part and I told you broadly dynamics is the all kind of movements which are taking place across the membrane. So, there are different transport phenomena which dictates the dynamics part of it or the dynamicity of the membrane because you have to realize that there are several molecules which has to be exchanged across the membrane. The water has to be exchanged. The salts have to be exchanged. At times there are nutrient like glucose which is the major energy currency has to be exchanged because we have to have the glucose intake. Then there is movement of several other small molecules across the membrane and this process has to be regulated with exceptional precision and clarity. Otherwise, we would not survive. Otherwise, we would not survive. Not only that cell needs to secrete out a wide range of molecules outside it. Some of these includes neurotransmitters which have to be secreted by the nerve cells to communicate with other nerve cells. There are endocrine cells which secrete hormones which takes care of a wide range of physiological functions which we deal with. Apart from it, the cell has to regulate its water. Sometime it has to take in water. Sometime it has to get rid of water. Sometime it has to throw away the toxic material from inside the cell so that it can survive. Apart from it, there are several other energy transduction processes which requires a lot of membrane dynamics processes which includes conduction which includes energy synthesis especially in the case of mitochondrial membrane in the case of photosynthetic membrane. So, what we will do in this section or in this lecture? First of all, we will broadly classify the different transport phenomena of molecules which regulates a lot of physiological processes in the body. So, broadly speaking, if I had to classify the different phenomena of transport phenomena the transport phenomena could be classified into two broad groups. One is energy dependent processes. The other one is energy independent processes or in other words one is without need for any energy. The other one is you need energy for the transport to take place. So, based on that there are two terms. One is called the passive transport where you do not need any kind of energy. There are physical constraints which leads to the movement of x y z molecules and there is active transport. So, broadly let me classify it in terms of the membrane transport. If I had to put it like this membrane transport it could fall under passive transport and active transport. These are the two broad and on a very very broad heading you can classify them and based on that if I had to diagrammatically show you and if I consider this as a cell. So, for example, this box structure is a cell with bilipid layer. So, one of the process of passive transport is diffusion then you have something called will come in depth with that. Facilitated diffusion then you have something called filtration then you have conduction. Then I am now putting something on red which is called active transport. This is I am putting into red purposefully because this is energy I am just putting it energy dependent phenomena. Whereas, the one I am now putting them as green are energy independent phenomena and within this broad heading you have some phenomena called exocytosis endocytosis and will come in depth endocytosis. So, these are the broad broad ways of you know classifying the different transport phenomena which takes place across the different membrane. So, now we will do again we will redraw that transport phenomena transport across membrane under the broad heading and first we will be dealing with a process called exocytosis. These are some of the key and endocytosis what is exocytosis and what is endocytosis exocytosis exo as the name indicates look at it exo. Exo means you are throwing out something outside the cell say for example, a cell has this is a cell and it has excess water it has a lot of. So, this is a cell and it has lot of water lot of water molecules. So, it has to throw away this water molecule. So, throwing out of this water molecules throwing out of materials outside the cell outside the cell falls under exo cytosis. This is one of the key phenomena which dictates the regulation of several fluids across the membrane. Next is endocytosis which is just the reverse of it endocytosis endocytosis endocytosis is of two kinds. So, first of all what is endocytosis. So, if this is the cell this is your cell and you are taking something inside the cell taking molecule inside the cell that is what endocytosis means. Endocytosis could be of two kinds endocytosis it could be called pinocytosis or phagocytosis pinocytosis or phagocytosis. What is pinocytosis and what is phagocytosis? Pinocytosis is a process by which a lot of fluid material is taken inside the cell fluid entry and whereas phagocytosis solid particle entry. This is the basic difference between pinocytosis and phagocytosis. This is the broad under the broad heading of pinocytosis and phagocytosis and they have a profound role to play. Whereas in exo cytosis exo cytosis is one of the regulatory mechanism by which a cell gives away neurotransmitter. The nervous signal the way the cell send the neurotransmitter it is by an exo cytosis process where as an endocytosis it takes stuff inside it. So, I expect that it should be very clear about these two words exo and endocytosis through an endocytosis. Taking outside the cell taking inside the cell this is exceptionally important. After this we move on to the next which is called a diffusion process simple diffusion sorry this diffusion process is governed by the concentration variance. So, there are two or three factors which dictate diffusion say for example, let us think of a situation out here there are two chambers out here. So, this is say for example, chamber A this is chamber B. So, within chamber A you have a wide number of these greens are the molecules which are presenting chamber A and along with you know a lot of water molecules out there or some kind of a solvent out there. So, what is happening in this in this side the concentration of this green molecule where to say the concentration of the green molecule is very high. So, invariably what will happen these green molecule will try to diffuse to the other side into chamber B they will move like this. These green molecules will try to you know diffuse and equilibrate on both side. So, there will be intermediate situation and eventually you will see this B side will have equal number of green moving from one side from side A to side B and vice versa. This is the basic understanding of diffusion which is extremely important for people to understand that this is one of the processes transport phenomena which is the simplest of all. So, what are the factors which affect. So, for example, let us like this the effect of pore size on membrane permeability. In other word what we are going to deal in this situation is what are the factors which dictates your diffusion. Diffusion is being governed by permeability how much the membrane is permeable permeability of the membrane pore size. This is extremely important what is the size of the pore third is the membrane area or what is the area covered by the membrane fourth one is thickness of the membrane. So, if your area is more say for example, you have more area than I am just putting into upward arrow. So, the possibility that the diffusion will be more provided the pore size support set. Say for example, you have more cross section to travel or in other word the membrane is very thick say for example, something like this. So, there will be a slower diffusion. So, based on this several kind of equations could be derived that how the membrane is what are the pore sizes and what are the selective things and based on that certain things can pass certain things may not be able to pass. So, it is kind of a very dynamic process and this helps us to look at cells look at natural things where they become selectively permeable because it allows say for example, a membrane may allow carbon dioxide to pass may not allow a bigger molecule to pass through or it may allow water to pass it may not allow some other gas to pass through it likewise. So, there are several variations across nature and this is exceptionally important for us to understand this whole diffusion is governed by this simple factors permeability pore size cross sectional area overall area the surface area and all these different parameters and based on that one can develop any form of equations by which you can really understand the whole process of the whole membrane dynamics how the molecules are criss crossing across the membrane. From here we move on to the next phase that is called filtration. Filtration is a much more simple process. So, for example, filtration is divided is sorry filtration is a function of the hydrostatic pressure. So, you can filter something from one side to another side provided there is a pressure difference and that will flow through. So, it is a direct function filtration is a is directly governed by hydrostatic pressure. In other words, this hydrostatic pressure is the governing force in taking care of the filtration. So, if I say this difference in hydrostatic pressure is shown by delta p that this decides what will filter through apart from this there is another factor that what are the pore size we dictate what will filter through. So, for example, if your filter size is say 2 micron and you have a molecule which is 4 micron. So, whatsoever pressure you give most unlike likelihood of 4 micron molecule will pass through 2 micron unless otherwise the molecule can shrink through and get through by some way some means or other or say for example, you have a pore size of 0.2 micron and you have molecule which is like 10 micron there is no way that 10 micron molecule which is. So, huge can pass through a 0.2 micron filter. So, the pore size is exceptional important the pressure you are putting across the 2 side is exceptional important. So, one of the key role is played by the hydrostatic pressure and the pore size and of course, again all the parameters will coming to play the surface. The amount of surface which is exposed with the filter and the cross section of the filter and all these things and it is a very hot area of research where several innovative filters are getting inspiration from biological component. They see natural phenomena natural filtration assemblies and they get inspiration to develop next generation of filters. So, third thing we are going to deal with is called osmosis which is a very specialized form of diffusion. If I had to it is a it is a basically called a special case of diffusion special case of be very careful on this one because many people kind of get confused with what osmosis is all about try to put it refers to the diffusion of water or any other solvent or next page any other solvent down its concentration gradient this is exceptionally important. Concentration gradient of water water once again of water arises whenever there is unequal concentration there is a concentration of particles unequal concentration of particles across a membrane across this is extremely important that is permeable. And this is another important aspect of osmosis that is permeable to water but please highlight this but not to the particles in other word I am highlighting this word not to the particles in other word we are talking about a semi permeable or or selectively permeable membrane. So, if I had to draw this it is something like say for example, I think this is not the right way to draw it say for example, here is a membrane and this is the membrane this membrane will allow water to flow on both sides likewise, but if say for example you have these particles different kind of particles or say for example, you have these red and green balls what you could see out here it would not allow the red or the green balls or any other kind of particles which are present these are different particles it will not allow any of those to pass through it. So, their mobility of these these red green or this magenta color balls and everything will be concentrated they would not be allowed to pass through it. And this is the situation when you will see osmosis phenomena taking place and if I had to put it in terms of word then you say the non diffusable the what I showed you the non diffusable particles this is extremely important please get your basics very right on this non diffusable particles which I was drawing like you know the red and then the green and the magenta and all those non diffusable particles exert exert and osmotic pull osmotic pull on water sorry sorry I just have to once again I am just missing on the track just kindly pardon me because I just missed the slide yeah osmotic pull on water that can be the second that can be quantified in terms of osmotic pressure this is extremely important for you people to understand which is sometimes denoted with pi the sign that this osmosis phenomena it is an specialized diffusion process which is dictated by the process of the osmotic gradient of water. But this diffusion phenomena takes place through a selectively permeable membrane this selectively permeable membrane does not allow the solutes to pass through it only allows certain solvents to pass through them. And this phenomena is so very important that this is the same phenomena by which some of the most important example we all urinate we do not lose a lot of water and from the kidney this does not happen because kidney the role of osmosis you could see in kidney in urine formation we retain a lot of water ok we have a very concentrated urine this is called water retention this water retention in the kidney is an example classic example of osmosis phenomena then we know this blood capillaries which are carrying blood all over our body they do not lose a lot of fluid fluid loss is controlled fluid loss is controlled in the capillaries by by the osmosis process by by the osmosis process and this is governed by this is governed by several proteins which are present and I am showing in the dot these are the several proteins which are present and same way in the kidney there are whole bunch of proteins which are present which pulls back the water and does not allow the water to be lost. So, this is the important of this whole process osmosis which is a specialized diffusion and please be careful it is the force exerted by the non diffusible particle and on water and that is called the osmotic pressure exceptionally important for you people to understand and clarify this thing from here we move on to let us classify all the different. So, another before we classify it let us talk about another form of transport phenomena that is called conduction anyway this conduction phenomena we are going to come in bigger detail very soon while we will be talking about the nervous system conduction. Conduction phenomena is like this the flow of these sodium potassium and using different kind of pumps where the sodium is being thrown away and potassium gets in. So, these are the channels let me put them in red the channels let me put some kind of channels. So, these are the channels these are the pumps these are the pumps. So, this kind of process where electrical ionic conduction taking place the ions are moving and those ions lead to the generation of electrical impulses which is our lifeline like in the heart which will be on next topic actually where the heart impulses are regulating the heart beating. And the nerve impulses which helps us to communicate with or send any form of information from outside our body to the brain and even from inside our body to the brain and ask the brain to respond back these are all taken care by the specialized membranes of the nerves and the muscles and under the muscles. Of course, you have the smooth muscles from the gastrointestinal tract you have the cardiac muscle from the heart and you have the skeletal muscle from all over your body. So, these are specialized membranes and we will be talking about these membranes as we will be talking about the nervous nerves and their function and everything we will be talking about in depth about it. So, at this stage I am not getting far into that. The next one there is another term we talked about osmosis we talked about diffusion and then under diffusion we talked about osmosis. Then we will talk about another word which will come across called facilitated diffusion what does this mean? The word itself is self-explanatory something which facilitates a process something which it promotes the process it is something like this let me draw it that will make it say for example, this is the membrane there and there is a transport protein sitting like this say for example, and this is your membrane what I have drawn. Let me just put the color the membrane in green this is the membrane and in red you see a transport protein. Now, what happens say for example, something has to be transported across it by a process of diffusion. So, what happens is this and this is the protein out here the molecule say for example, is denoted by say black these molecules. So, these molecules go and bind here likewise this. So, once they bind here and they adhere on this surface and then this particular protein changes its conformation and what you see next is this. So, this is outside and this is inside and this is again outside this is inside. Now, you have transported those molecules inside which is taken bear or facilitated by this is falling under facilitated diffusion they fall under bigger heading of facilitated diffusion. So, if I had to kind of you know classify the mechanism and the driving force which I am going to do for the passive transport. So, this is what I will do before I move on to active transport passive transport I am classifying passive transport as mechanism the driving force driving. So, you have diffusion you have filtration you have osmosis you have you have transverse. So, these are the major ones and conduction is taken care by the voltage gradient osmosis is taken care by the concentration gradient of water filtration is by hydrostatic. So, this is the summary hydrostatic pressure diffusion is by concentration gradient of both solute and solvent. So, these are some of the overall outline and talking about the facilitated diffusion let me just go back. So, this facilitated diffusion is extensively used for in glucose transport will come we will come back to all these things as we will be going through the course glucose transport in our body in the intestine and other places is being taken care by facilitated diffusion process. So, now from here we will move on to the active transport processes. So, now we are moving from as of now we talked about all the processes which are non energy dependent they did not need energy active transport active transport needs active participation of energy rich molecules like ATPs. So, these are the energy dependent transport sorry energy dependent transport phenomena energy dependent transport phenomena you have two kind of active transport one is called primary active transport and you have secondary active transport. So, what is primary and what is secondary. So, now we will next slide we will talk about the primary active transport. So, primary active transport are taken care by ion pumps. Let me give you a example in we will talk about the ion pumps you remember I was telling you in the last class. So, if this is the cell and this is inside and this is outside. So, there are bunch of pumps which takes care of likewise which are sitting there which changes their conformation and ensures that the flow of potassium and throwing away of sodium from the cell and thereby maintaining the homeostasis of the cell these ion pumps are primary active transporters they help in and they are completely tell you ATP dependent. If you remember in the last class I told you they are ATP dependent and ATP has to be present inside the inside the cell ATP dependent and I talked about one of the molecules called oven which blocks these ion pumps. So, these ion pumps are extremely crucial in the Nobel laureate Jan Skaou who actually discovered the structure of them got a Nobel prize for it. Realize that these ion pumps are the ones which decides the potential difference across a cell across especially across as a matter of any cell. So, they ensure inside the cell we have lesser amount of sodium we have lesser amount of glucose we have higher amount of potassium we have higher amount of few other molecules as compared to outside where the glucose is higher your sodium is higher amino acids is lower whereas, amino acid inside the cell is higher. So, these all these different kind of phenomena are all these different kind of variations especially with the sodium and potassium is being governed by the primary active transport which uses these kind of pumps. So, now from here we will talk about the secondary active transport secondary active transport secondary active transport are often used two types one is called co-transport the other one is called counter transport counter transport. So, and as we will move into the course we will come across several situation of co-transport and counter transport. So, at this stage what I will do is we will just give you a brief idea about co-transport and. So, one of the simple example is that the movement of sodium ions along the concentration and voltage gradient that is established by sodium and voltage gradient that is established by sodium potassium pump can be used to pull another substance along with it in a process called sodium sorry sodium. I just miss the slide bear with me in a process called sodium co-transport. So, along with this another substance is being carried this falls under sodium co-transport. So, we will come in depth about many of these. So, some of the examples where this co-transport and counter transport phenomena are being used I need it to highlight is in especially in the kidney in the kidney glucose absorption. So, that we do not do the absorption then in the intestine glucose absorption these are all secondary active transport these all are secondary active transport phenomena. The rate limitations of this transport phenomena the limitation of transport mechanisms is with the depending on the carrier proteins and the overall composition if you look at it inside and outside the cell. So, you will see sodium will be lower inside the cell potassium will be higher amino acids will be higher outside sodium will be lower potassium will be sorry I am sorry sodium will be higher potassium will be lower glucose will be higher outside the cell glucose will be far more higher outside the cell. And among the total body fluid there are these body fluids are being distributed in two compartments either it could be intracellular or extracellular. So, major concentration of water is in the intracellular fluid and lower concentration is outside to the extracellular fluid. So, this brings us to an conclusion about our second section of the topic which is memory and physiology of nerve and muscle. What I expect is that you should have a very clear idea about the structure of the membrane the different components of the membrane which includes the lipids which is the major component including the glycolipids and the phospholipids apart from it you should understand the lipids are classified as storage lipids and membrane lipids. And we are talking about the membrane lipids you should have a fair understanding about the role of cholesterol then you should understand the role of the proteins membrane proteins how they are embedded and how within the lipid bilayer with the non covalent interactions. And the examples I cited about valenomycin and gramacydein which are probed to understand how the probably these proteins have evolved and several toxins which has the channel forming ability. I give you an example of an anti carrier antibiotic. Apart from it expect you to have an understanding about the carbohydrate molecules which are decorating the outer surface of the cell membrane which helps the cells to identify the given identification mark to the cell the help in whole bunch of chemotaxis and whole other techniques. And you should have a fair understanding about different techniques which are being used which I talked about lipid vesicle lipid bilayer studies and freeze fracture technique fluorescence technique to understand the mobility of the lipids and the proteins across the membrane. And from there you should have a overview about the different dynamic processes or the transport phenomena which includes the passive transport and active transport across the membrane which include diffusion osmosis conduction facilitated diffusion exocytosis endocytosis. And in the active transport you have primary active transport and secondary active transport within the secondary active transport you should have there is co transport there is counter transport. So, overall with this basic understanding I assume we will enter into our next topics which will be much in depth, but the whole basis lies here. So, with this I will close in the lecture and we will start with the next topic next thanks.