okay today we're actually going to talk about membrane dynamics This chapter focuses on basic terminology that you're going to get familiar with and use throughout the term Yeah So here are the silos Here are the objectives So understand the difference between transport systems Identify the different type of passive as well as active transport and of course the characteristics Distinguish between endocytosis versus exocytosis Distinguish between lian gated channels and voltage gated channels Again um distinguish between uniolar support and antiportar So uniport simport and antiport And lastly distinguish between hypotonic isotonic and hypertonic Now let's kind of focus on the transport systems There are various types of transport system that a cell uses but the main ones that we're going to talk about in this um chapter at the moment is going to be passive transport active transport and endoccytosis Exocytosis endoccytosis and exocytosis is classified or falls under vicular transport So let's talk about passive and active transport When you describe passive and active transport there's two things that you need to keep in mind One does it utilize energy that's one question you have to answer when you're talking about passive and active transport The second one is which direction is the solute going now I'm not talking about if it goes up or down I'm talking in regards to the concentration gradient So let's classify passive transport based on those two um principles Passive transport does not use energy Why because solute is going from area of high solute concentration into an area of low solute concentration In physiology when something is going from high to low we say that it is going it's it's sorry it's going down its concentration gradient Okay So passive transport we answer the two questions Does it use energy no it does not Which direction is a solid going it's going down its concentration gradient Meaning it's going from an area of highly concentrated into an area where is fairly concentrated or low concentration Now let's talk about active transport Active transport is complete opposite of passive transport But again you're going to be answering those two questions So does active transport use energy if it's complete opposite of passive means yes it does But why why does actor transport utilize energy the reason is solute is going from an area of low solid concentration into an area of high solute concentration So solute is trying to go into an area which is already crowded And anytime you're squeezing into or trying to go into an area which is already crowded you have to basically invest energy Okay So active transport is a process in which solute is going from area of low solid concentration into an area of high solute concentration And to do this it requires energy In physiology when we say something goes from low to high we say it goes against its concentration gradient Okay Now there are two types of um passive transport diffusion and osmosis and we'll talk about what they mean in just a sec There are two type of active transport primary active transport and secondary active transport Once again we will talk about them in just a sec Let's quickly just at the moment take a closer look at vicular transport There are two types endocytosis and exot cytosis Um vicular transport is able to transport large molecules and several different types at the same time We will discuss this a little bit later Okay Now let's take a closer look at diffusion Diffusion is a type of passive transport Diffusion is a process where solute is moving Okay So where is solute going from an area of high solute concentration into an area of low solute concentration Meaning the solute is going down its concentration gradient The key term is down in passive transport There are three types of passive transport Uh sorry there are three type of diffusion Lipid or simple diffusion channel diffusion and facilitated diffusion Lipid diffusion is mainly reserved for lipid soluble substances meaning anything that can dissolve in lipids versus channel and facilitated diffusion uses a membrane protein to actually transport the solute So this image basically shows you the three different types of diffusion lipid channel and facilitated As you can see regardless of which one we're using solute is going from an area of high solute concentration into an area of low solute concentration Now you can see that lipid diffusion does not use any extra assistance meaning there's no help from a protein where channel and facilitated is using proteins Why is it channel and facilitated diffusion does not use protein i mean sorry where channel and facilitated does use protein but lipid does not The reason lipid does not is because the substance is lipid soluble in our plasma membrane is lipid So anything that can dissolve in lipid easily crosses by where in um channel and facilitated the substance that we're trying to transport is lipid insoluble It cannot dissolve in lipid Therefore it needs assistance It gets help from proteins Okay Now what is the difference in the protein that is utilized in channelneled versus facilitated if you look at the image in channel diffusion the um the protein is actually hollow in the middle and it allows substance to actually move through when facilitated diffusion basically the channel is going to change shape during the process okay and I'll talk about that uh later okay let's focus a little bit more on channel diffusion at the moment so channel diffusion uses carrier protein which are hollow in the middle as I mentioned it's primary use for ions and water why ions because ions are charged and therefore they're insoluble in lipid Now there are two types of channel diffusion There's non-gated channel and gated channel Non-gated channel means that the channel does not have a door Its transport is not regulated and that is mainly used for water Why water is freely able to go in and out We're gated channel means that the channel has a door and therefore the transport is regulated Only when the door is open can something go in and out What is channel um or gated channels mainly used for it's mainly used for transporting basically ions Why ions because they have a charge As you know ions there's a cation and there's an annion Cations ions have positive charge and ions have negative charge and you don't want charges to really go in and out because that's going to actually change the entire chemistry It's going to change the charge of your membrane which can be dangerous Therefore they have to be regulated Only when it is time are those channels going to open up allow something to actually go in or out And when I say something else so right here we can look at the channel um non-gated channel Right here is a plasma membrane and right here you have a channel embedded in the plasma membrane And you can see this is the hollow part This hollow part there is no gate on it And because there's no gate something can really just go in and out Here's the interior of the cell Here's the exterior Because there's no gate meaning like a door something can go in and out Okay So let's look at the channel in uh the let's look at the gated channel So again here is a plasma membrane and right here we have the gated channel embedded in the plasma membrane outside the cell inside the cell You can see here is a hollow part and this hollow part is actually gated So these are the doors Right now these doors are closed So solute can't exit or cannot enter the cell When So imagine that this gate is open Imagine the red is gone and now this basically the door opened up and because now it's freely open solo can go in and out of the cell meaning the gate is open Now there are two types of gated channel And why are there two types it's basically what unlocks the gate So the two types are lyen gated channel and voltage gated channel Make sure you get familiar with these names It's very important So there are two types of gated channel Lyen gated channel versus volage gated channel Okay Let's talk about basically the different type of gated channels Let's talk about the light gain gated channel So right here you can see the plasma membrane Here is basically the lien gated channel which is closed at the moment And because it's closed nothing can go can go in and out Now basically you can see the channel is open and something can either go in or out So what allowed the channel to go from a closed state into an open state it is binding of a lian What is a lyan ligan is something physically has to bind to the protein It could be a hormone It could be a neurotransmitter Okay So as soon as the lyant binds to its receptor on the protein it causes this protein channel to open up allowing something to go through So imagine a lien gated channel as basically a classroom which is locked You would not be able to enter the room unless the instructor doesn't come there uses a key to open up the door That would be an example of a light gated channel Now right here let's look at a voltage gated channel Right here you have a plasma membrane embedded right here is a voltage gated channel Right now the channel is closed Therefore you can see sodium cannot come inside the cell In this state you can see the channel is open and now the sodium was able to enter the cell So what allowed the sodium to enter what allowed the protein to open up it is the change in the membrane potential Right here the charge of the membrane is 70 m volts and right here it went from 70 to 50 m and that change in the charge caused the channel to open up So voltage means a charge Okay So example think of a volcage gated channel as a elevator Let's say you're on campus until 11 o'clock at night You're the last person You're studying on the third floor and now it's 11 So you go to the elevator assuming you're able to use them You get in you press first floor Is the channel going to open up on second floor no it's going to open up only on the first floor This is how world page gated channels work Regardless if we use lighten or wage they actually transport ions Now let's uh look at lipid diffusion Lipid diffusion is basically used by substances which are lipid soluble meaning they can cross the plasma membrane without any assistance Why because of our plasma membrane is a lipid What usually uses lipid diffusion another name for lipid diffusion is simple diffusion Gases are the ones usually that use lipid diffusion Example oxygen carbon dioxide Even ura which is not a gas but ura is lipid soluble and it actually uses lipid diffusion Now let's look at facilitated diffusion So in facilitated diffusion actually what happens the membrane changes shape during the process So something will bind to the um protein and when I say something it's something that you want want to transport Example let's say um glucose Glucose will bind to basically the protein causing the protein to change shape And when it changes shape something or glucose has now been transported So um this right here is basically a hyperlink that will show you how facilitated diffusion works So imagine this is let's say glucose that we want to transport My hand is basically the protein the facilitated um channel diffusion plasma membrane plasma membrane outside the cell inside the cell and my um hands which are the proteins are embedded in the plasma membrane Now imagine this glucose thing that we want to transport it's outside the cell right now Now it binds to basically the protein Okay as you see now it's bound As soon as it bounds the protein actually changes shape and by doing so something is now inside the cell Same would work in opposite direction As soon as the transport material binds to the protein the protein changes shape and now something is outside the cell This is how facilitated diffusion works Okay So um try to do question one You will notice I do have questions for you guys within the lecture Okay So what type of channel would you call that it's like gent Now how did I come to that answer what were the clues in this case scenario it says the diabetic drug works by binding to the channels The key word was binding and causing the channels to open up and ions were able to be transported So because the drug actually now binds to the protein causing the protein to open up or the channel to open up allowing ions to be transported This is why it's considered lyen Now let's talk about osmosis Osmosis is basically passive transport but in osmosis it's water movement Okay not solute Diffusion is solute movement Osmosis is water movement Now where does water go water goes to an area where there's more solute So water always leaves an area of low solute concentration enters an area of high solute concentration So I think of um osmosis as basically a new freshman in high school If it's a guy he gets attracted to the jocks If it's a girl she gets attracted to the cheerleaders So they always go to the popular crowd So osmosis basically is water movement where water always goes to area of high soluble concentration Um so right here you can see basically two cubes There's A There's B There's A There's B In area A we have 1 2 3 4 5 solute Okay Right here we have about 10 So which direction does water go water leaves this low concentration enters the area where is high concentration So you can see water left area A entered area B Okay Now because water moves the concentration of the solute changes not that the number of particle changes it's a concentration Okay So what do you think happened to the concentration of the solute in um part A versus part B so the concentration in part A increased because water left and the concentration in part B decreased because water entered So anytime water leaves an area the solute concentration in that area increases Anytime water um enters a area the solute concentration in that area decreases Okay let me give you an example Imagine you're at home and you basically just made you know you have sugar water You taste it but it's not sweet enough Now you need to make that solution sweeter but you don't have any more sugar to add So how would you go about making that sol that solution sweeter you would boil it right after letting it boil for 10 minutes you taste it The solution is sweeter Correct do you add any sugar to it no But why is it now sweeter it's because water evaporated or water was gone Okay so keep that in mind Now because Water enters leaves and you change the concentration There are different tonicities and tonicities explain the concentration of solute So there are different tonicities you can have and you use this terminology to explain which area has more solute So there is hypotonic isotonic and hypertonic Hypo means less iso means same and hyper means greater amount So let's look at it When you say something is hypotonic okay let's call all of these cells Let's call all of these cells So when you say something is hypotonic that means that area has less solute than the other Okay so in here okay you can see A is hypotonic compared to B Why because A only has 1 2 3 4 versus B has about eight So A is hypotonic compared to B Now let's look at isotonic Isotonic means both areas are equal in concentration So you can see this has four this has four So both of them are same meaning isot time Um the way to remember iso has s stands for same Now let's look at hypertonic Hypertonic means that area has greater amount of solute than the other Now just when you think of the word hyper doesn't actually just mean that person is too excited Okay it's too much That's what it means So when you look at these two cells A is hypertonic compared to B Yeah Because it has greater solid concentration compared to here And of course you could use this terminology in um opposite way So you could say A is hypertonic to B or you can say B is hypotonic compared to A But usually you are comparing two or more substances or um solutions So now let's see if you understood this um concept Let's try our problem We have three different solutions Okay we do not know what the concentration of these solutions are So one of them is hypotonic one of them is isotonic one of them is hyper But we do not know which one is which Now to these solutions I added red blood cells Okay When the red blood cells were added to solution A the red blood cells actually decreased in size When I added the red blood cells to beaker B there was no change in the size of the red blood cells But when I added the red blood cells to beaker C or solution C basically the red blood cells increased in size Now looking at the appearance of the red blood cells or the size of the red blood cells you can figure out what the tunicity of each of these curve is So take a minute and then we'll go through the answers Okay So solution A is hypertonic Solution B is isotonic And solution C is hypotonic How the hell did we figure that out okay so osmosis is water always goes to the area of high solute concentration So when we basically placed um red blood cells in solution A they decreased in size Why did they decrease in size because they actually lost water Why did they lose water well because um the solution actually had to have more solute compared to the red blood cells So the water inside the cell got attracted to the solute outside because it was highly concentrated So water left the cells enter the solution and this is why the red blood cell decrease in size Therefore the solution is hypertonic compared to the red blood cells Now let's look at B the isotonic because there's no change in the size of the cell meaning water did not enter or leave Why did it not enter or leave because both sides are equal in concentration and C the solution was hypotonic again Why the cells increased in size why did it increase in size well because water entered Now why did water enter water entered because there was more solute inside the red blood cell Therefore water got attracted came inside causing the cell to enlarge Meaning that the solution had to be hypotonic compared to the red blood cell So here's a slide um with the correct answers Okay So now we're going to do this but backwards I have again you have the three beers with three different solutions and you have the red blood cells But this time around I'm telling you what the tonicity of each solution is and you have to tell me what happens to the size of the red blood cell when the cells enter those solutions So take a minute and we'll talk about it Okay So the case tells you that this solution is isotonic This solution is hypertonic and this solution is hypotonic because this case tells you So now what happens to red blood cell when they're put into basically solution which is isotonic nothing the cell remain the same size So that they remain the same because both areas are equal in concentration Now what happens to red blood cells when they enter a solution which is hypertonic they tend to decrease in size Why because this area has more solute compared to the cells inside the cell And then what happens to um red blood cells when they're placed in hypotonic solution they increase in size Why because the red blood cell had more solute compared to the solution Therefore water entered the cell So B was decrease in size and C was increase in size And here are the answers You should be able to do such um or be able to answer such questions on the exam Now we're done talking about passive transport Now we're going to focus on active transport So active transport is basically a process in which um solute is going against its concentration gradient meaning from low to high And because it's going from low to high it requires energy There are two types of active transport primary active and secondary active So let's look at primary active transport Primary active transport system basically uses ATP as energy That is the main difference between primary and secondary What is used as energy in primary active transport ATP is used as energy and I'll explain what is used as energy in secondary So right here you can see something is going from low to high and to do that ATP is converted into ADPI meaning ATP was used the energy was used and here you can see this is going from low to high this is going from low to high again ATP is converted into ADP and PI meaning energy was used same right here something going from low to high something is going from low to high and to do that it's using ATP okay that is primary act transport system ATP is utilized as energy so this is basically a prim um sodium potassium ATPs pump is classified as a primary active transport pump so right here you have a cell here's a cytoplasm outside the cell we have high levels of sodium and low levels of potassium Inside the cell we have high levels of potassium low levels of sodium And here is the sodium potassium pump This transport sodium and potassium This pump is classified as a primary active transport pump So your function is to figure out between sodium potassium which one enters which one leaves the cell How can you figure that out based on the concentration because as I said this is a primary act transport system So take a minute and then we'll talk about the answers Okay So in sodium potassium pump sodium leaves the cell and potassium enters How did you figure that out or how do we figure that out as I mentioned this is basically a primary active transport meaning both of these solutes have to go to area where it's highly concentrated So you can see there's high sodium outside the cell So sodium has to go outside or leave the cell There's high levels of potassium inside the cell So potassium has to come inside the cell because everything is always going against this concentration radian And because this is a primary active transport pump ATP is used as energy So you can see ATP is broken down to ADP and PI So here's basically the answer This is a slide you can look It just um shows how sodium potassium pump works more in detail Um I'm not going to exactly ask you this but just for your reference Sodium potassium pump is very important pump You will basically come across it um every single day basically in physiology as well as the terminology we used in this term example um for today example passive transport active transport lian ga channel won't voltage gated channel lipid diffusion all of these terminology should become like ABCs to you because we will um talk about them every single time we meet and I'm not going to be explaining exactly what they mean every single time you should automatically know that Okay Okay So now let's talk about secondary active transport So after transport that uses indirect form of energy Okay So you can see something is going from um excuse me low to high but there's no energy being neutralized Something is going from low to high Again there's no energy being utilized But this is the active transport So what is the energy the energy is indirect form of energy So what happens in secondary active transport the first solute goes down its concentration gradient collects energy to transport the second one against its concentration gradient So you can see right here the square is going from high to low When it does that it collects energy This energy is used to transport these yellow circles from low to high Yeah Even in this example you can see squares are going from high to low Okay and when it does that it collects energy And this energy is used to transport the yellow ovals from low to high This is basically secondary active transport So imagine um primary and secondary So imagine you're going to go to the airport to pick up your friend who's come going to come and visit you So you go to the airport pick her up You're using your time your gas money That is considered primary active transport You're personally investing energy Now trying to get a um idea of secondary active transport Imagine so you're going to basically go pick up your friend from the airport but your mom is going to actually take a flight out at the same time So she's like "Hey you're going to the airport Can you just give me a ride?" So you're like "Of course but you're a nice person So while you're going to go pick up your friend from the airport you take your mom so she can take a flight." Did your mom use her gas her time no you did So that is secondary actor transport You invested the energy She basically just hitched a ride Okay that's secondary active transport Okay three terminology that you should become familiar with Uniport simport means only one type of solute is being transported either it's entering the cell or it's leaving the cell Okay uni means one Simp and antiport are terminology um reserved for um transport proteins where two or two solutes are being transported Simport means both of them are moving in the same direction So right here you can see this is caused by a simple both of them are leaving the cell or both of them could be entering the cell Antip port is reserved when both of these solid are going in opposite direction meaning one is entering and one is leaving These terminology uniport simp if it's passive or active transport All it says it kind of tells you are the solutes going in same direction or in opposite but nothing about pass over active transport Okay Okay Let's talk about indo and exocytosis which is vicular transport So it basically uses vesicles to transport something and this material is usually large when you're trying to transport and you can transport multiple things at a time So exocytosis sounds like exit Okay Endoccytosis means enter So exocytosis something is leaving the cell Endoccytosis sounds like inside meaning something is coming inside the cell So imagine your cell just produced some protein and you need to ship that protein to let's say another cell maybe your liver cell So this is the protein you just produced and you basically package that um in a vesicle So here is the solute the red are basically what the protein you make and this um phospholipid blayer is basically the package This collectively is called a vesicle with its content So this vesicle migrates to the plasma membrane As soon as it arrives to the plasma membrane it fuses Why plasma membrane is a phospholipid billayer This vesicle is a phospholipid billayer So both of them fuse As soon as the vesicle has fused with the plasma membrane this material is now outside the cell Okay So this was exocytosis exit Now endocytosis So that protein you just made finds its way to the hypatite the liver cell Now it actually has to enter the liver cell That is endocytosis So these molecules that you're trying to um the molecules that are trying to come in the protein basically aggregate at the plasma membrane and because they start to bunch up at the plasma membrane the plasma membrane starts to invaginate and it keeps on invaginating until a vesicle can be pinched off and now this vesicle is inside the cell So you have transported the material from outside to the inside which is endocytosis So this is primary active transport Why because it tells you utilizes ATP Automatically you know this is primary active transport So this is simple because it tells you sodium and chloride are transported into the cell So both of them are entering the cell meaning in the same direction So it's simpler Okay this slide is for you So I kind of explained active and passive transport You're going to use that knowledge to basically fill in this chart trying to organize your thoughts And of course some of the words have been filled in trying to direct you in the right direction Now the last part we're going to talk about is basically total body water So the total body water is split up into two main compartments Intercellular and extra cellular Sorry it should say intracellular and extracellular Okay I apologize It should say intracellular Extracellular Intracellular fluid is fluid inside the cell and it's highly concentrated with potassium Extracellular fluid is fluid outside the cell and it's highly concentrated with sodium Now the extracellular fluid is split up into intersticial fluid and plasma Interest fluid is fluid between two cells where plasma is fluid found in the blood cells But both of these are outside the cell Therefore it's classified as extracellular fluid So right here you can see You have intracellular fluid which is 1/3 of the total body water Then you have extracellular fluid which is 2/3 of the total body water Extracellular fluid is broken down into two small compartments Interest which is found between cells and um plasma which is found within blood vessels So identify um A B and C in this image So A in the image is intracellular fluid B in the image is basically um plasma and then C is basically intersticial fluid because it's fluid between two cells B and C would collectively collectively be called as what so D would be classified as extracellular fluid and we are done with membrane dynamics Okay this recording will also help you prepare prepare for your basically lab quiz um in week two as well as prepare you and help you understand the concept that we you will demonstrate in week two lab