 Plasma proteins are proteins which are dispersed as colloid in plasma, that is they are not actually dissolved in plasma. They are fundamentally classified into three fractions based on their various physical and chemical characteristics and these fractions are albumin, globulin and fibrinogen. Also globulin further is of three types, alpha globulin, beta globulin and gamma globulins. Apart from these there are various other proteins as well though. Also note that almost all plasma proteins are synthesized in liver except gamma globulins. So you should assume that plasma proteins except gamma globulins are synthesized in liver until stated otherwise. Now as you might be aware that our capillary membrane is permeable to movement of water and ions. However the capillary wall is impermeable to proteins. So the proteins stay in the capillary and the blood and do not move to interstitial fluid unlike the ions which can freely move across the capillary wall. And that is the reason that plasma proteins exert an osmotic pull of water towards the capillary and hence retain the water in the blood vessel. And that actually ions they are present on either side of the capillary wall. So proteins exert an effective osmotic pull towards the capillary. So you can guess that if concentration of protein decreases the osmotic pull decreases and this will cause water to move into the interstitial fluid causing edema. Now apart from this very important function plasma proteins have many other functions as well. So first function we have stated that is exertion of on-cortic pressure which helps maintain the plasma volume and this on-cortic pressure is mainly exerted by albumin. See the size of the albumin is very small. So with a similar concentration of other proteins what will happen that there will be more number of particles of albumin and since on-cortic pressure is dependent on the number of molecules and not on the size of the molecules, albumin forms the most significant protein for development of the on-cortic pressure. And next function of plasma proteins is that they act as binding and carrier proteins. So they help in transport of many substances in blood. For example albumin. Albumin binds many substances non-specifically and carries them in blood. For example various hormones, amino acids, fatty acids, then bilidubin and many other substances. Then there is a globulin actually it is the alpha and beta types of globulin which act as carrier proteins and these globulins in contrast to albumin they bind with specific substances. Albumin we said it binds with substances non-specifically globulin binds with specific substances. So there will be a globulin which binds with say thyroid hormones so that is known as thyroid-binding globulin then there is steroid-binding globulin. Fine. Then there are other proteins also for transport of substances like ceruloplasmin for transport of copper, transferrin for iron, haptoglopmin for transport of cell-free hemoglobin then hemopixin which binds to porphyrins. So various proteins act as binding and carrier proteins. Then next function is in coagulation because some proteins act as clotting factors while other proteins act as inhibitors of coagulation for example fibrinogen which we said that it is a major faction. This fibrinogen forms fibrin and obviously there are other clotting factors as well. Along with this the proteins which act as inhibitors of coagulation are also present for example antithrombin 3. So they are clotting factors and there are inhibitors of coagulation. Then plasma proteins contribute to viscosity of blood especially the protein fibrinogen and you remember here that actually the viscosity depends on the shape of the protein. We saw that on-potty pressure depends on the number of the particles or number of the molecules but viscosity depends on the shape of the protein so fibrinogen is an elongated derphebrillar protein and that is why it contributes most to viscosity when plasma proteins are considered. Then next the plasma proteins are important for immunity and inflammation. See the gamma globulin which we said earlier they are basically antibodies secreted by B lymphocytes. So we know the role of antibodies in immunity but apart from this there is alpha 1 protease alpha 2 macroglobulin which are protease inhibitors so the help in limiting the inflammation. Then proteins act as buffers and are responsible for 15% of buffering capacity of blood. Also note that at normal plasma pH of 7.4 most plasma proteins exist as anions and that is why they can easily buffer hydrogen ions and it is important because our body is more equipped to handle increase in hydrogen ion rather than decrease in hydrogen ions. For this concept that how various buffers act I have made another video and the link for which I have given in the description section below you can check that out also for the detailed knowledge of action of buffers. Fine let us move to another function. The plasma proteins especially the alpha globulins serve as inactive circulatory proteins which are in turn activated by other substances example angiotensinogen is an alpha globulin and you know that angiotensinogen is converted to angiotensin 1 and then angiotensin 2 and it causes so many functions in body. Fine so these are the major functions of plasma proteins. With this let us see some clinical applications of plasma proteins. So first is albumin globulin ratio. Normal albumin concentration in body is 3.5 to 5 gram per deciliter while that of globulin concentration is 2 to 3.5 gram per deciliter. So if we take a ratio of their concentration it comes to 1.5 to 2.5 is to 1. Now we have said before that except gamma globulin rest of the proteins are synthesized in liver. So can you guess what will happen to albumin globulin ratio in case of liver disease? Yes synthesis of albumin will decrease and it will cause a decrease in this ratio. The decrease in albumin globulin ratio can occur in liver disease. Not only that there are many other diseases also which can affect this albumin globulin ratio. Let us go to second application. We said plasma proteins exert an osmotic pressure and an important for maintaining plasma volume. So if plasma protein concentration decreases as happens in malnutrition or malabsorption of amino acids or decreased synthesis of plasma proteins as in liver diseases or increased loss of plasma proteins as in nephrotic syndrome. What will happen to an oncotic pressure? Well the oncotic pressure is going to decrease and this will cause fluid accumulation in interstitial space that is etymal. Fine then we saw in the functions that one very important function of plasma proteins is transport of substances. Now this is applicable to drugs also. So in cases if plasma protein concentration decreases as we have seen in various cases so in liver disease or kidney disease what will happen that the free concentration of drugs which bound to plasma protein will increase. See when the drugs are administered a percentage of for the drugs bind to the plasma proteins and a percentage of them in the free form. So it is the free form which are responsible for the action of the drugs. Now if the plasma protein concentration decreases what will happen? The binding of the drugs to the plasma proteins is going to decrease and suppose if the binding decreases from 99% to 98% the free concentration of the drug will increase from 1% to 2% so their actions and side effects will also increase. So we have to be very careful while prescribing drugs especially which bind to plasma proteins a lot and we have to revisit their dose in various conditions in which plasma proteins decreases. Then as I told that plasma proteins act as important buffers also and at plasma pH of 7.4 they are mainly acting as anions. So suppose there is alkalosis that is pH is shifting towards this side that is increasing. In this case more proteins will exist as anions and this will increase the unmeasured anions and if you know the concept of anion gap what will happen that there will be increase in anion gap because of increase in unmeasured anions. So we have to interpret the values carefully. Then finally plasma proteins are used for treatment as well for example in diseases in which clotting factor deficiency is there for example hemophilia then in that case the concentrate of plasma proteins so in hemophilia case concentrate of factor A is obtained from suitable donors and they are administered and there is something known as cryoprecipitate also which is having a mixture of different proteins and if this factor A it is not available separately then this cryoprecipitate may be given. So that was all about the various types of plasma proteins, various functions of plasma proteins and if you understand the functions then also the different clinical applications of the knowledge of plasma proteins. Thanks for watching the video, if you like the video do press the like button and please do share the video with your friends whomever you think that they should have this knowledge and don't forget to subscribe to the channel Physionity Open, thank you.