Full transcript of “Cell membrane / Plasma Membrane Structure and Function (Detailed Lecture)”. Click a timestamp to open the video at that moment. Need another video? Use the YouTube transcript generator.
0:02 Assalam Walekum, in today's lecture we will study the cell membrane in great detail and after doing this lecture your every concept of cell membrane will become crystal clear. So let's start with the cell membrane. The cell membrane is also called plasma membrane or cell surface membrane. Whatever name it is given, it is the same thing. Its nature is semi-permeable. That is, what is this cell membrane? It is selective as to which molecules are to be allowed to enter inside and outside the cell. That is why it is called semi-permeable membrane. And it is present around every living cell of life. That is, all the living cells will have cell membranes. The reason for this is that the cell membrane is very important to maintain the environment inside and outside the cell. If the cell does
0:49 not survive, it is very important. But we had studied in the previous lecture that animal cells do not have a cell wall. So the outermost part of the animal cell is The boundary is the cell membrane whereas in plant cells, bacteria and fans, there is a cell wall inside it. So, this cell membrane is also present inside the cell wall. So, you have to understand what is cell membrane. It is the boundary that surrounds the cell. It surrounds every living cell, but in animal cells, it is the outermost boundary. It is clear now. Let us discuss some important functions here so that it is easy for us to understand the further concepts. What is the function of cell membrane in me? This cell membrane provides support to the cell and how does it provide support? This side
1:36 also helps in making its return. It provides support and also provides mechanical strength. It is a little selective as to which molecule is to be allowed entry inside and outside the cell. So, its nature is very important because the nature of the environment inside the cell is different. The outside environment such as extra cellular flood, also known as interstitial flood, is more different. So, to maintain this nature, the cell membrane is such a barrier that it knows which molecule to send inside the cell and which molecule to keep outside the cell. You have understood simply. Now we move towards structure and composition, that is, what is its structure
2:23 and what things it is made of, it is called composition. The model of structure, in 1972, Singer and Nicholson presented that the structure of the brand in the cell is like this and that model is called a flood model. What is the natural nature of the cell membrane? In this way, the important molecules of the cell membrane keep moving easily from one place to another and why is it called mosaic? It contains some proteins which are regularly raised and also form sumo jack patterns. So, due to this reason,
3:10 it is called flood mosaic model. Here you can see that this layer which you can see is a black coloured layer, it is called lip layer, so this is a fat layer, there is bread on top and bread below as well, okay and it is also called a concept, Vikas, there is a phosphate group in it and the oil region is
3:55 also called fatty acid oil, Vikas, there are fatty acids in it, okay so head and oil region, now because of this first fat group, this head region which is polar, has a charge on it and because of this charge it is hydrophilic, it is water loving, Vikas, a slide charge is also formed on water, so like this concept you have to take here that the collar head is hydrophilic, it is water loving and the fatty acid is nonpolar, it runs away from water, like when you put oil inside water, so in the same way you have to take the concept that the fatty oil is hydrophobic, it is nonpolar and the first aid of fastfolipad is a bowler and there is hydrophile
4:41 and phosphate in it. And fatty acid because it is a lipid, these two molecules are present, that's why it is called fatty acid. This fatty acid is of a different type. It is either saturated, or saturated fat, or this acid will be oil or unsaturated fat or acid will be present in it. So if it is saturated fatty acid, then that oil will be very straight. If it is unsaturated fatty acid, then that oil will be a little banded in this way. There will be king in it because of the presence of double and triple band. Okay, here you can see that this is unsaturated. This oil is a little banded. Okay, here we have to take the concept that if we drop the oil of this tree inside the water, then how will it attach to the oil of the nearby tree
5:29 that its head will get attached to the water and its oil will run away from the water. Here the head is formed with water and the oil gets attached to it, the oil is going away from the water. Okay, in this way it is clear. Now you must have understood that the environment inside the cell is like We can say that there is flood present in the intracellular environment, that is, there is flood inside the cytoplasm, there is water. In this way, it has formed its structure. That is, it has its powder in the area where water is present, there is flood there as well, there is water there as well, so the
6:15 head of the fluid there is attached to the side and outside. So this is a very beautiful concept that the polar head, whether it is the inside portion of the cell or the outside portion of the cell, the portion of extracellular fluid, and this is very important because if there was oil here, then the water molecules would not be able to come even close to it. So, if there was any enzymatic activity near the fluid in the cell, it would not have been possible. It is clear. So, we have studied the fluid bill and found that there are two layers of fluid, brother, there is a layer of fluid, whose head, the polar head, is outside, the 2-layer liquid area of the body, whether it is the outside area of the cell or the inside
7:01 area of the cell, it is clear. Apart from this, I have told you about the fluid head. I told you that proteins are also present in mosaic pattern, so these structures of red colour represent proteins and you are seeing these proteins, they are present between the divisions of cell membrane and some proteins will be present in the cell, in the password area, in the head area, there are different types of proteins, glycoproteins, cholesterol, let's see them one by one, so you have understood the structure of cell membrane, in it two layers of phospholipids are attached in such a way that their hydrophobic oil is merged with each other so that no polar molecule can enter from here, polar molecules
7:48 cannot enter because it is hydro phobic and it neither allows water nor polar molecules to enter, it is made up of proteins, where I have told you and the cholesterol is present here, it is the owner of integral protein, protein is integral
8:36 protein, it is also called protein, transport protein is also called trans membrane protein, glycolipid and glycoprotein are also present that if The carbohydrate molecule which is representing glyco will attack with protein, then that molecule will be called glycoprotein, so these molecules are also present, apart from this you will not find anything else inside the cell membrane, now let us understand this and every molecule and what are their functions, let us see in such details,
9:27 I have told you the structure and what is the structure of cholesterol which is polar, okay, and its region is which gets inside with the oil, okay, what does it mean to maintain fluidity, we know that there are
10:20 some factors on cell, temperature and cholesterol, so if the temperature is high, then the fluidity of cell membrane will increase or decrease, we will study this now, what will be the effect of fatty acids which are of two types of unsaturated, on fluidity and what will be the effect of cholesterol on fluidity, we will study this, so these are some factors which affect fluidity, first factor A If the temperature is high, what will the phosphorus molecules do? They will move away from each other. You can take this concept that when it is very hot, you run away from the other person, try to sit far away because the heat that is coming from the radiation hits you in summers. When it is hot, the molecules
11:08 in the cell will go closer to the brain, then the fluidity of the cell membrane will increase. So if the temperature is low, what will happen in low temperature, the phosphorus molecules will come closer to each other. What do you do in winters? You have to sit together so that the heat is transferred to each other. So, you have to take this concept here that the molecules of phosphorus come closer to each other due to the cold temperature. If they come closer, the fluidity will decrease, that is, if they join together, then the fluidity of the cell membrane will decrease. The second factor is to study fatty acids. There are two types of fatty acids, if there is more unsaturated fatty acids inside the cell membrane. So the fluidity in your cell membrane will increase, what is the reason,
11:56 I told you that there is a band in it, so for example, if you are standing with your leg bent, then the other person cannot come and stand very close to you because your leg has to be kept in between, what is the band of fatty acid doing, it does not allow the other fatty acid to come too close, so more cream will not come, so due to more unsaturated fatty acid, there will be an increase, the answer will be very simple, then the other molecule will be able to come closer to it, so the fluidity there will decrease, it is clear now let's move towards the college role, remember cholesterol is such a molecule, if you ask me any question,
12:41 what is the role of cholesterol inside the cell membrane, then you have to answer that it is such a molecule that maintains the homeostasis of the fluidity of the cell, that is, the owner of cholesterol has to maintain the fluidity, that is, if the temperature is high, then it does not allow the fluidity to increase, if the temperature is very low, then it reduces the fluidity a lot. Kamini allows the cholesterol molecule to be maintained at its level, but for example, if the temperature is high, then what should have happened is that if it is possible that the molecules move away from each other, the fluidity in your cell membrane becomes very high, which is not good for the cell membrane, because everything looks good in a balance that the molecules in the cell membrane move away from each other, the fluidity increases a lot, but when cholesterol is
13:27 present, then the cholesterol attacks the molecule and does not allow it to move, which is its property, if that is not there then the fluidity will decrease, I have told you very simply, if the gas of high temperature becomes very low, then what happens to the molecules wrapped around phosphorus, they come very close to each other, they get attached to each other, the fluidity decreases, right cholesterol, those molecules will come very close to each other, the fluidity will decrease a lot, but if the cholesterol molecule is present, then this molecule would sit on the side So the other phosphatidylcholine will not allow the molecule to come very close to the cell membrane. So if that gap remains, what will happen is that the fluidity will be maintained. So the fast cholesterol molecule plays a
14:14 very important role in high temperatures, so maintain the fluidity of the cell membrane. Well, what is the benefit of maintaining the fluidity of the cell membrane? The fluidity should be maintained so that there is no gap in the cell and it does not become too open. If the fluidity becomes very open, it means that any molecule will be able to enter from the outside. If there is too much fluidity, then no molecule will be able to enter. And it is necessary to maintain fluidity, that is, to keep it in a balance. This is because many nonpolar molecules, such as oxygen and carbon dioxide, which are very small particles, enter through the fast wall membrane, inside and outside the cell. So, the
15:06 molecules of oxygen and carbon dioxide easily enter in and out and this is very important to keep it open. So, this is the reason why the cell is cleared. We have studied the role of the lipids in the membrane and also seen their function. Now let's move on to the membrane proteins. What is the function of membrane proteins and what are they doing? Which are the different types? So I told you that there are two types of them. Integral ones are present. Transmembrane or Transport or Enteric are given different names. These are proteins. And the peripheral ones are also called proteins. So these are two types of proteins. Now what is the function of these proteins?
15:52 Now as I told you, nonpolar small molecules enter there but some large molecules are unable to enter from here. There are some water molecules. There is a tunnel inside it, a region. So this membrane protein cannot pass glucose from here. So this membrane protein helps
16:40 it enter inside the cell. In this way, the function of membrane proteins has been explained. [Music] Okay.
17:30 And what will microtubules do to it? Microtubules are present there. For example, you know, these micro tubeless peripheral proteins are present. It attacks with these and so a pulse is formed from the skeleton inside the cell due to which the structure of the cell is
18:17 maintained by reading the additional pressure, this cell membrane has a Panchak Shakti inside but these micro TVS become like a pulse just like you put pillars etc. under the floor, so in the same way these are the pillars inside the cell, micro tubes which are attacked with these proteins, so it means that the protein of the brain in the cell also helps in making its return, okay we have studied the membrane lipid as well, we have also studied the membrane protein, now what are these proteins and what is their function, glycolipids, I have told you that the molecule of carbohydrate plus lipid is called glycolipids and the molecule of carbohydrate plus protein is called glycoprotein, now what is their function, here I have to mention two important functions,
19:04 first of all the receptor molecule which is also called cell signaling, that is, a glycol effect and The molecules of glycolipids and glycoproteins are involved in the reception. What does reception mean? It attacks the cells in the body and can activate the activities. For example, hormones and neurotransmitters work in this way. If this is a nurse cell, then it attacks the pattern of cyanide junction protein, then the other cell gets activated and it gets activated and the signal is transferred to it. So this is called cell signaling or cell signaling. The second important function of
19:51 glycolipids and glycoproteins is cell to cell recognition. That is, all the cells in your body have these glycolipids on them. These are of a specific type. Your immune cells that keep moving around in your body can remember your cells because of the pattern of these glycolipids. I will tell you an example of this. If there is a person who is wearing the uniform of a Pakistani soldier, then you will be able to recognize him by looking at him that he is a Pakistani soldier and a If a person is wearing the uniform of an Indian Army, you will recognize him as an Indian Army man because the patterns of the uniform are different. In the same way, your immune cells know the pattern of the cells present in your body. For
20:40 example, we have A and B of blue group system. What are antigen B in this? What are the specific patterns of glycolipid and glycoprotein? So, if you get a blue transfusion from a person whose blue group is different, then a reaction starts inside your body. The reason for this is that your immune system has to prepare for the pattern of glycol and glycol protein on it. This is not our body's own cell. The sourced reaction response starts. Apart from this, if we get the functions of cell membrane, that is, the membrane is a cell membrane like chloroplast mitochondria. So, the
21:27 membrane of chloroplast also contains some pigments which help in photosynthesis. In this way, there are two concepts of respiration inside the wall of mitochondria, I have already made a detailed video on this, you can watch it by searching, so that too, after attacking the cross-linking of the blood in the cell, it sends the chemical out of the cell and makes it enter from outside, so I have already done that, let's review what we studied today
22:13 and what was its function in the cell membrane, I told you that there is a membrane of semipermeable nature which is present around every cell, but in animals there is a boundary structure, I have told you its flood model is presenting its structure and in composition, we read that it contains lipids, proteins which are forming the blood in the cell, what are their functions, there are two types of cholesterol and these lipids maintain the fluidity of the cell membrane and this fluidity has to be maintained, hence it is important now so that the nonpolar membrane
22:58 gives entry, thank you Allah.
