Receptors & Intra-cellular Signalling – Made Easy

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Receptors & Intra-cellular Signalling – Made Easy

now my very dear friends today we are going to talk about receptors you know receptors are very special macromolecules which are present within our body and different ligands work on them now we have to first discuss what is like and what is the receptor right ligands mean ligands mean the substances which bind with receptors the specific receptors for example all the hormones in your body are acting as ligands hormones all your neurotransmitters all your neuro transmitters neuro transmitters are also ligands then all the drugs would use the also bind with certain receptors so they also work as ligands so we can say all your hormones and neurotransmitters and drugs and even toxins all of them bind with specific receptors to produce their effects because they have to bind with special receptors right so we call them ligands toxins and even some other chemical molecules chemical substances now all these ligands have to work on a receptor let’s suppose this is a receptor right now what really happens that receptor has one point to which our ligand binds these ligands are supposed to bind with a very unique point and this point where these ligands bind these points are called ligand binding domains what are they called this is a receptor and this part of the receptor to which a ligand bind right this part of the receptor is called yes ligand binding domain right now once a ligand binds with ligand binding domain of a receptor then receptor is supposed to produce some biological actions receptor will produce certain biological actions biological activity biological actions or biological activity in the body is modified now again let me repeat what is receptor the sceptre is a macro molecule another way to define the scepter is receptor the macro molecule to which a particular ligand binds and then receptor undergoes some transformational change and produces biological effects on the body the point which you have to remember is that if hormones or neurotransmitters or drugs or toxins or chemical substances bind with some other substance they bind with some other substance right but this does not result in any change in the body or biological function this should not be called receptor look for example their plasma proteins many drugs or hormones or toxins are neurotransmitter they tend to bind with the plasma proteins but once the drugs are chemical substances or hormones when they bind with the plasma proteins plasma proteins do bind with these ligands but plasma proteins do not produce any effect on the body because plasma proteins do not produce an effect on the body so we say plasma proteins are not receptors is that right again let’s repeat what we have discussed up to now let’s recap what is the receptor receptor is a macromolecule receptor the Necker molecule in a biological system to which a certain ligand binds like in maybea hormone or neurotransmitter or drugs or toxins or other chemical substances and once the ligands bind with a specific receptor that will result and some biological motif kitchens in the organism this is that right now listen if you don’t have a clear concept of the chapter you really don’t understand how the hormones work in your body you don’t understand how neurotransmitters work you don’t understand how the most of the drugs work even you don’t understand how the most of the toxins work so if really you want to understand action of hormones and neurotransmitters drugs and toxins fortunately or unfortunately you have to understand how the receptors work what are the receptors what are their classes

how do they work right now first of all we’ll talk about two basic types of receptors you see all the substances which are going to work on the receptors we have given a name of ligand to them now all the substances which have which have to produce an action on a cell they can be broadly classified into two groups for example let’s suppose here is a cell yeah this is a cell right now on the cell let’s suppose there’s a hormone number one hormone number a and here’s a hormone number B Harma harmony and harbin be these two hormones have to work on this receptor and modify the action of this cell again there’s a hormone the a the hormone B or ligand a or language ligand B and these ligands are going to act on the cell and modify the function of this cell a question is that that there are two types of basically ligands some which are large molecular weight which are large molecular weight and some of them are highly yes polar highly charged now those ligands which are large molecular weight like peptides for example peptides or those ligands which are highly polar like catecholamines they’re highly child molecules they cannot dissolve into lipid membranes because these substances cannot dissolve in the lipid membrane so both of these substances they cannot enter into cell due to their big size or their high charge because they cannot enter into cell so if they have to modify the action of the cell they have to have their receptors on the surface of the cell these ligand has to work on the surface of the cell again all those neurotransmitters or drugs or hormones which are large molecular weight and which are highly polar or either they cannot dissolve into lipid membranes of the cells they cannot enter into cell because they cannot enter into cell so their receptors should be present on the surface of the cell the receptors should be expressed from the surface of the cell so this receptor this receptor is cell surface receptor or it is a protein which is expressed from the surface of the cell membrane opens to that there are some you can say ligands which can directly enter into a cell they can directly enter into a cell these are highly these are either small molecular weight substances small molecular weight substances or they are highly lipid yes the highly lipid soluble of such substances which are either very small or they are highly lipid soluble right they can dissolve the lipid membrane and enter into cell and because they can enter into cell so their receptor should be present yes within the cell their receptors should be present within the cell that’s the beauty of it that all those substances which usually cannot enter into cell their receptors are expressed from the cell surface and all those substances which can enter into cell their receptors are present within they may be in the cytosol or within the nucleus this is a right now next time if I asked you that there’s a substance which is very large in highly polar this receptor should be present on the surface and if I say that there is a substance which is highly lipid soluble and which is very small molecular weight it’s a separable present within the cell the receptors should be present within the cell which means primarily we can classify receptors receptors expressed from the surface of the cell and receptors which are present where in the cell right so this is the basic classification of receptors now I can give you some very interesting examples of those substances for which in acceptors are on the surface for example peptide hormones peptide hormones for example yes you know many peptide hormones like yes in saline everyone knows about insulin growth hormone prolactin FSH yes at latch here search and so many others oh these

substances are large peptide they cannot enter into cell so their surplus will be present on the surface of the cell opposite to that another group along with that there’s another group of compounds which are highly charged which are highly charged for example catecholamines Katie Cola means catecholamines for example yes epinephrine right or norepinephrine or dopamine right all of these are highly polar if these are highly polar highly charged can they enter into cell no so there is hapticity present on the surface of the cell the same way either you can talk about a stale choline yes there are so five hydroxy tryptamine is rotten in there the histamine there is prostaglandins then there are many so many substances all of these are not soluble enough to enter into cell so their receptors to be present on the surface of the cell opens to that there’s some substances which are really highly lipid soluble there are other substances which are highly lipid soluble this should not remind you official now policy right and small molecular or small molecular weight substances a substances which are highly soluble their receptors are present within the cell what are the examples of such substances fine all thus harm on the substances which are derivative of cholesterol morally speaking all the substances which are derivative which are called steroid hormones now steroid hormones yes steroid hormones are highly soluble now it means steroid hormones will work on the surface of the cell or within the cell answer is within the cell right now what are the can you name few steroid hormones of course there are so many for example yes testosterone progesterone progesterone estrogen yes then there is testosterone progesterone estrogen then there is aldosterone aldosterone then there’s glucocorticoids and even you know what I mean D is basically a derivative of steroid like structure so we can say vitamin D what is the special name for vitamin D Coley Kelsie for all what is the special name for vitamin D Coley Kelsie flow is there right now all these substances are highly lipid soluble so when they act on the target cell the freely moves through the membrane the receptors are present within the cell and they are they act right now then the other substances which are very small molecular weight for example t3 t4 these are tyroid hormones or you can talk about retinoids retinoids are vitamin A related compounds these substances are also able to cross the cell membrane so they’re a surplus should also be within the cell now we will go into detail of receptors we have already discussed that there must be two types of receptors number one the receptors which are expressed on the surface of the cell and receptors which are expressed within the cell is that right there are certain which are expressed from the surface of cell they are for those molecules which are highly polar and normal innovate and then there are receptors which is within the cell which are for small molecular weight ligands or which are meant for a highly lipid soluble ligands now the we will start discussing you know receptors we have said it you can say within the cell membrane and these are within inside the cell inside the cells now first I will discuss all the receptors which are expressed on the cell membrane right now we will go into detail off those receptors which are expressed on the yes surface of cell membrane now let’s suppose this is a cell right and this is the surface of the cell the many types of receptors which are expressed from the surface of cell I will just talk about the most important groups one whole family of the receptor is like snakes you see they are made by a very large you can say peptide and this peptide 7 times passes in and out of the

cell membrane look what is this this is a receptor and this receptor consists of a long peptide chain and which passes in and out through the cell membrane how many times seven times right and it has one domain outside this is extracellular domain and it has one domain which is inside and this is called intracellular domain right this group of receptors are called because they look like snakes right they are a very special name for such receptors they call them serpentine receptor serpentine receptors serpentine means something like yes please snake something like snake right this is a serpentine receptor right and they have also one simple name for this type of a scepter these receptors are also called yes sir pretend receptors are how many times will pass through the membrane seven times so we call it seven pass receptors so I really love this name because it easy to remember that it’s seven times passes but my kid is like this one they don’t know how dangerous a serpentine so the thing serpentine receptors are good anyway there’s a very big family of receptors right and they pass through the cell membrane seven times right they have extracellular domain and they have intracellular domain extracellular domain as ligand binding domain to this point what will bind ligand will bind ligand will bind to this domain right and when ligand binds here it activates this receptor is that right when ligands binds on this it activates this receptor so this domain is called what is the name of it ligand binding domain AAPIs to that once the ligand binding on it is stimulated then intracellular part will start giving signals to the cell it will start giving signal to the cell so this part is called yes what should be the name of it because it is going to produce effects in the cell so this part of the receptor which is going to produce ultimate effect on the cell this part of the receptor is called the factor yes domain so what did we learn that 7/5 receptor like other receptors have ligand binding domain and they’re having factor domain ligand binding domain is outside the cell affective domain is inside the cell well I can’t bind with the ligand binding domain there’s a change in the receptor which is transmitted to the effector domain and effector domain give very unique signal to the cell right now life is not so complex tat everything has to pass seven times there are other group of a scepter whole family of receptors where a scepter is very innocent it passes only once the scepter passes only once through the membrane there’s no way to pass it seven time they passes only once through the cell membrane because they pass only once through the membrane so their name is also very simple they should be called yes one pass receptor they should be called one pass receptor right these receptors should be called one pass receptor right another way of course then what happens that here is the ligand which binds here yes this is the ligand here is the ligand which bind with the ligand binding domain were likened by bind with the ligand binding domain then effector domain start giving yes signal to the intracellular varmint is the right what is this domain effector domain an effector domain will start giving signals within the cell these are one pathway thickness right there many substances work on the one path receptor and there many substances work on the seven path receptor for example the substances which welcomed seven pass receptor there are so many I will just give you few examples like catecholamines catecholamines every medical service know there is epinephrine there is not a pina friend yes there is dopamine all of them work through seven pass receptor all of them work through serpentine receptors even do you know that s still choline has muscarinic receptors which are seven

paths receptors which are to the family of seven path receptors even prostaglandins they have seven path receptors again histamine seven path receptors you can talk about five hydroxy tryptamine that is also which is also called swat I mean that also work on the seven path receptors and then you can talk about yes there’s so many substances like catecholamine a.style choline prostaglandins system mean 5-hydroxytryptamine would you like to know that even psh hang on work on the sound paths receptors so there are many substances which works with a unique family of receptors expressed on the surface of the cell and this family is called serpentine receptors or other name is seven pass receptor but one very interesting point which I would like to highlight here all of these acceptors are coupled with very unique type of protein within the cell this protein is having alpha component beta component and gamma component this is a primary protein this is a primary protein it has three peptides this primary protein specially its alpha component it binds with a special energy powered guanine gtp you know GTP binds with where UTP is binding with the G protein G protein consists of alpha unit beta unit and gamma unit this black is the G protein and this is gtp molecule if gtp molecule is binding here it is very rich in energy and it becomes active or if one phosphate is broken then it is GDP then again it’s an energy level of GDP is low so GDP at IG protein is an active now listen alpha beta gamma I do not make our trimeric protein which can bind with GDP or gtp right if it is binding with the GDP it is a low energy level if it is binding with gtp it is a high energy level and because these proteins are binding with the GDP or gtp they are simply called G proteins they are simply called yes please G proteins thank god some doctor did not put the name of this protein on his personal name or daughter’s name they simply call it G proteins so what are G proteins you proteins are unique type of intracellular primary proteins to which GDP or GTP binds is that right and these are called G protein now remember one thing very interesting that all the serpentine receptors are working through different type of G proteins all the serpentine receptors work through G proteins that is why there is a third name for these proteins these receptor and that is g-protein coupled receptors g-protein coupled receptors now listen carefully in your MCQ if you see there the word of serpentine receptor we are talking about this receptor if they mentioned seven paths receptor again it is the same system or they call it g-protein receptors it is the same system why the College serpentine because it looks like a snake why I call it seven paths because seven time it peptide passes through the cell membrane why they call it g-protein coupled receptors because these receptor that intracellularly connected with the and working with the g-proteins is that right now I would like again come back to one path receptor one path receptors have as unique effector domain and you need this effector domain is enzyme because this is enzyme so other name for one path receptor is enzyme-linked receptors enzyme-linked receptors now look here it is seven paths susceptor it is one path receptor it is g-protein coupled receptor it is on Zion coupled receptor this is that right