hey everyone welcome back once again to my educational channel on biology i'm teacher janet and today we'll be discussing two subtopics from from four chapter three okay 3.2 passive transport versus active transport so what are the differences between these two types of uh movement of substances across the plasma membrane okay so the earlier part of 3.2 has been discussed in another video this is the last order the later part of it then uh 3.3 is a very short subtopic which is uh entitled passive and active transport in organisms okay in the living organisms so when we talk about passive transport we can compare it to an analogy okay of a person riding a bicycle downhill huh so when a person rides the bicycle downhill he doesn't have to use energy at all because the bicycle will by itself move downhill due to the pull of gravity right so this can be compared to passive transport which also does not involve the use of energy huh that's why it's called passive passive means the person is uh doesn't move around much right so in passive transport energy is not required right and another comparison we can make with this person who is cycling downhill is that the person cycles from a height the higher height to the lower height okay from the higher part of the heel to the lower part of the heel right so for active for passive transport for passive transport molecules move from an area of higher concentration to an area of lower concentration all right and this process does not require energy for the movement okay so remember when you think of passive transport think of a person cycling down here whereas for active transport is the opposite it's like a person who is cycling uphill all right so if you have ever tried to cycle uphill or climb up a mountain and climb up a hill you will know that it can be quite tiring okay because you have to work against the force of gravity now you have to move against the force of gravity which is pulling you down so a lot of energy is needed for you to cycle uphill or to climb up a steep hill right so likewise active transport requires the use of energy for it to be carried out okay it's just a comparison and secondly when we cycle uphill we are moving from an area of uh that is at a lower level to an area that's at a higher level from low to high so in active transport molecules move from an area or region of lower concentration to an area of higher concentration from low to high so this is a good way of remembering what active transport is okay like a person cycling uphill from low level from a low level to a higher level okay right so let's carry on and find out more about the differences between passive and active transport the learning standards for today's lesson are as follows 3.2 concept of movement of substances across a plasma membrane the learning outcome or standard is compare and contrast passive transport and active transport secondly for the next subtopic 3.3 movement of substances across the plasma membrane in living organisms firstly we must be able to explain by using examples the process of passive transport in organisms and secondly explain by using examples the process of active transport in organisms here is an easy concept map to help us remember the movement of substances across the plasma membrane so the movement of substances across the plasma membrane is divided into two basic types which is passive transport and active transport so number one passive transport is the process whereby molecules move down the concentration gradient from an area of higher concentration to an area of lower concentration and it does not need energy for it to occur okay whereas in active transport molecules move against the concentration gradient so it's the opposite way molecules move from an area of lower concentration to an area of higher concentration low to high all right and this needs energy okay so for passive transport it's divided into three types right simple diffusion osmosis and facilitated diffusion in which facilitated diffusion needs the use of carrier proteins or channel proteins for it to occur then for active transport there's only one type active transport it uses carrier proteins okay and it needs energy to occur so the acronym for the four types of movement of substances here is sulfur s for simple diffusion o for osmosis f for facilitated diffusion and a for active transport now let's quickly recap the four methods of movement of substances across the plasma membrane or the four types of movement of substances across the plasma membrane which are simple diffusion osmosis facilitated diffusion and active transport okay according to the acronym sulfur s o s o f a so the first type of movement is called simple diffusion which is the movement of molecules or ions from an area or region of higher concentration to a an area or region of lower concentration right so for the cell simple diffusion occurs through the phospholipid bilayer of the plasma membrane right and what are the types of particles that can move through the phospholipid bilayer using simple diffusion now these are lipid-soluble molecules such as fatty acids and glycerol oxygen and carbon dioxide and also other lipid-soluble molecules like vitamin a d e and k right so all this can diffuse through the phospholipid bilayer by simple diffusion all right now the second type of movement of substances is osmosis right so for osmosis it's just the diffusion of water molecules or molecules of a solvent through the phospholipid bilayer again from region of higher concentration to region of low concentration or down the concentration gradient okay so water molecules diffuse through the phospholipid bilayer right so thirdly we have facilitated diffusion the word facilitated means this type of diffusion needs the help of a channel protein or carrier protein meaning the transport proteins right for the substance to move across the plasma membrane so the first example is uh the first type is facilitated diffusion using channel protein right so here's a channel protein it has a straight uh tunnel or channel that's how we recognize this channel protein right and then uh what type of substances move through the channel protein okay these are lipid insoluble substances such as ions charged ions like calcium ions chloride ions diffuse these substances diffuse across the plasma membrane by facilitated diffusion using channel proteins okay so these ions are small enough to move through the channel however for bigger molecules they use the carrier protein okay to move through into the cell to move through the plasma membrane so carry protein can change shape also it's unlike the channel protein which cannot change it so the carry protein will change shape to transport the molecule large molecule okay from region of higher concentration maybe outside the cell to region of lower concentration in the cell right so the molecules that can be transported by the carrier protein are large molecules such as amino acids and glucose that diffuse across the plasma membrane by facilitated diffusion using carrier proteins so simple diffusion osmosis and facilitated diffusion all of these are forms of passive transport that do not require energy for them to occur because substances move down the concentration gradient from region of higher concentration to region of low concentration okay however there's one more type of transport which we call active transport where substances move the other way around from region of lower concentration to region of higher concentration right and this needs the use of energy provided by atp it also needs a carrier protein that will change shape when it receives energy from atp in order to transport the substance such as ions okay into the cell as an example so an example of active transport is the transport of potassium ions by the carrier protein into the cell okay with the use of energy from atp such as in the sodium potassium pump okay and in the sodium potassium pump we also have the transport of sodium you can also transport sodium ions out of the cell from region of lower concentration of sodium ions in the cell to region of higher concentration of sodium ions outside the cell the opposite way okay so that is the sodium potassium pump right so this type of transport of substances which is active transport requires energy because the substances are moved against their concentration gradient from region of lower concentration to region of higher concentration all right that needs energy all right let's look at this question which is also a learning standard compare and contrast passive transport and active transport five marks so this is an spm question and we have to know the similarities and differences all right and write it down for this question because compare and contrast here is a command word that means that we must give the similarities and the differences all right between these two processes so firstly at least have one similarity both processes occur in living organisms and both processes involve movement of substances through a semi-permeable membrane in living organisms all right because living organisms have the plasma membrane right that is found on the external part of the cell right so that is where substances can move across either to go into the cell or to come out from the cell so here we see the structure of the plasma membrane with the protein molecules all right and here we see three types two types of active of passive transport two types of passive transport uh using the poor protein carrier protein and also one more way is if uh substances move through the phospholipid bilayer from region of higher concentration maybe outside here to region of low concentration in the cell here we see another type of transport which is active transport okay which requires energy provided by atp and it also needs a carrier protein right which can change shape to allow ions or molecules to move into the cell or out of the cell right so we have studied these processes of passive and active transport in the previous videos so now let's look at the differences firstly from the aspect of the concentration gradient in passive transport substances move down the concentration gradient or according to the concentration gradient that means from region of higher concentration to region of lower concentration okay whereas uh inactive transport substances move against the concentration gradient that means they go the opposite way where uh substances are moved from region or area of lower concentration to region of higher concentration like cycling uphill right and it requires energy okay whereas passive transport is like cycling downhill where no energy is required okay as the bicycle will go downhill uh be pulled downhill due to the force of gravity now passive transport in passive transport energy is not required at all that's why it's called passive transport right a passive person sit down sits down and doesn't move around much so he doesn't use up energy now in active transport energy is required to carry out the process all right because substances are moved against the concentration gradient and this movement requires energy now final outcome in passive transport the final outcome or the end result is that a dynamic equilibrium is achieved and then the process of passive transport will just will not be carried out anymore i will stop so what i mean by a dynamic equilibrium is when the substances have the same concentration in the two areas that were involved overall they have the substances are at a distributed evenly in the system now for active transport there is an accumulation of molecules and ions on one side on one side of the plasma membrane or disposal meaning elimination of molecules okay so either accumulation of molecules or ions in the cell or disposal or elimination of ions and molecules out of the cell now as for the carrier protein for simple diffusion and osmosis substances move through the phospholipid bilayer and they do not need a carrier protein to in order to carry out these two processes but if we are talking about facilitated diffusion which is also a type of passive transport carrier protein or channel protein is needed okay a protein molecule is needed to assist the movement of the substances either carrier protein or channel protein now for active transport it requires the use of a carrier protein that will transport the ions or particles into the cell or out of the cell so it requires the carrier protein and of course it requires energy for the carrier protein to change shape right now example you can always give an example for your table of differences okay and in this case we can say that one example of passive transport is the diffusion of oxygen from alveolus into blood capillaries which we will study in a short one and then for active transport two examples of active transport are absorption of mineral ions by root hair cells we'll discuss this in a short while and also transport of potassium ions into animal cells using the sodium potassium pump okay so you can give either one as an example now let's go on to topic 3.3 movement of substances across a plasma membrane in living organisms again this can come out as an spm question so there are two types of transport as we have said passive transport and active transfer so first let's look at the examples of passive transport in living organisms now passive transport does not require energy in organisms examples of passive transport in living organisms are number one gaseous exchange between alveolus and a blood capillary through simple diffusion okay gauges exchange occurs by simple diffusion in the lungs then number two absorption of water by a plant root hair cell okay and this is by osmosis right so it's a form of diffusion actually absorption of water but for osmosis it is the diffusion of solvents like water okay thirdly reabsorption of water through the renal tibial in the kidney by osmosis so this will come to we will talk about later in another topic okay and then now mostly if water is involved the movement of water is involved usually it's by osmosis i usually so the next one absorption of fructose molecule in village by facilitated diffusion okay this is not studied much but we have to discuss this as an example of facilitated diffusion in living organisms so we'll discuss this afterwards now for active transport and living organisms it requires energy and examples are examples in living organisms are the absorption of mineral ions by a plant root hair cell secondly absorption of glucose and amino acids in the villas please take note that for absorption of glucose and amino acids it requires energy entities it involves uh active transport uh whereas absorption of fructose okay in the villas is by facilitated diffusion for fructose is by facilitated diffusion so for glucose and amino acids the movement of the ions or the movement of these substances is by active transport and it's different but both occur in the village of the small intestine okay so next another example of active transport is the reabsorption of glucose through the renal tibial in the kidney again we will talk about that when we discuss it in another chapter and lastly transport of sucrose from leaf to fuller velum tissue okay so let's pick up a few examples to discuss we'll start with the gaseous exchange between an alveolus and a blood capillary through a simple diffusion so the first example of passive transport in living organisms is gaseous exchange between the alveolus and blood capillary by simple diffusion this process occurs in the lungs right so here we see an alveolus so an alveolus is a tiny asset in the lungs and the lungs contain a lot of alveolar line yeah i realize the plural form so let's look at just one alveolus now the alveolus has a wall called which is made up of epithelial such that is one layer thick right one cell tick on the wall and then uh on the surface of the alveolus we have the blood capillaries all right to carry out the gaseous exchanger glitches exchange with the alveolus so the avalanche has a layer of water or moisture on its inner surface so that the gases that oxygen i guess the oxygen can dissolve in that layer of moisture of water before it diffuses into the uh blood capillaries okay now let's look at the blood capillary so the blood that flows inner from the pulmonary artery okay actually comes from the body tissues okay so this uh this blood is the oxygenated blood because before this it has this blood was in the body tissues and it had allowed its oxygen to diffuse into the body tissues for cellular respiration so now it has lower concentration of oxygen okay because the oxygen has been used for cellular respiration so the blood is the oxygenated blood and it's denoted by the blue color here so this blood here has lower concentration of oxygen compared to the alveolus which has higher concentration of oxygen thus oxygen will diffuse from the avalus which has a high concentration of oxygen into the blood capillaries by simple diffusion thus the blood that flows back to the heart via the pulmonary veins will be oxygenated blood all right once the oxygen has diffused from the alveolus into the blood now so the blood becomes oxygenated rich in oxygen and it flows back to the are the pulmonary veins to the heart and from the heart to the body tissues all right so this blood will provide the oxygen to the body tissues again right so here we write you can state that the oxygen molecules diffuse from alveolus into blood capillaries okay from alveolus into blood capillaries down the concentration gradient or according to the concentration gradient okay by simple diffusion now how about carbon dioxide so the direction of diffusion of carbon dioxide is the opposite way compared to oxygen okay so the blood that comes in from the pulmonary artery okay into the blood capillary here has a high concentration of carbon dioxide okay because this carbon dioxide uh is actually from the body tissues that have carried out cellular respiration and produce carbon dioxide as a waste product as a by-product okay then the carbon dioxide diffused from the body tissues into this blood huh so now it's transported to the lungs and it's going to be excreted okay so how to explain the diffusion of carbon dioxide so we say the concentration of carbon dioxide in the is higher than the concentration of carbon dioxide in the in the alveolus thus carbon dioxide diffuses from the blood capillaries into the alveolus by simple diffusion down the concentration gradient or according to the concentration gradient okay so after that the carbon dioxide will be exhaled out or excreted from the body into the atmosphere so here are the notes to explain gauges exchange between alveolus and blood capillaries by simple diffusion right so we start with the concentration of the gases now the concentration or sometimes it's called partial pressure but that will be studied in a later chapter partial pressure so we use the word concentration the concentration of oxygen in the alveolus here is higher than that in the blood capillaries so oxygen diffuses from the alveolus into the blood capillaries down the concentration gradient from region of higher from the area of higher concentration to the area of lower concentration all right and this is by simple diffusion then another gas that we have to discuss is carbon dioxide okay so the diffusion of carbon dioxide is in the opposite direction compared to oxygen so again start with the concentration the concentration of carbon dioxide in the blood is higher than that in the alveolus thus carbon dioxide diffuses from the blood capillaries which has a higher concentration of carbon dioxide into the alveolus okay according to the concentration gradient or down the concentration gradient it's the same meaning right and so here we can see the change in the content of oxygen the incoming blood will be deoxygenated blood but the blood that flows out of the lungs will be oxygenated blood okay number two let's talk about another process of passive transport which is osmosis so an example of osmosis is the absorption of water into the root hair cells of a plant okay so here we see a plant and osmosis occurs at the roots here so if you enlarge one part of the root just enlarge one root hair cell okay that's on the epidermis of the root on the outer surface of the roots okay so first we start off by talking about the concentration of the water or the water potential now soil solution is where the roots are found right okay so the soil solution is the fluid in the soil and uh some solution we can say has a lower concentration of solutes than that in the cell why is that so because the cell set of the plant has a higher concentration of solutes due to the active transport of mineral ions constantly there's active transport of mineral ions into the cell and then into the cell set right so this will increase the concentration of the solutes or dissolved substances in the cell or in the cell set now if the cell has a higher concentration of solutes or dissolved substances like mineral ions then what happened to the water potential or the so-called concentration of water it will be lower because the concentration of water has is different just the opposite of the concentration of solutes you have a high concentration of solutes then you have low water concentration or low water potential okay now whereas on the other hand soil solution it has a low concentration of solutes or dissolved substances so it has high water potential higher concentration of water that means more dilute right therefore water will always diffuse from region of higher water potential a higher water concentration to region of low water potential all right so it will diffuse by osmosis water will diffuse by osmosis from soil water into the root hair cell okay that's how we explain osmosis involving the root hair cell involving water and the diffusion the diffusion of water into the root headset just follow one two and three huh here here are the notes for number two the second example of a passive transport which is the absorption of water into the root hair cells by osmosis right so firstly the soil solution has a higher water potential compared to the cell set of the root hair cell okay the soil solution here has a higher water potential than that of the cell set of the root hair cell okay because as we said the cell set of root hair cells has lower water potential because mineral ions are actively pumped by the root hair cells into the vacuum so this causes a high concentration of mineral ions in the cell set the ions are the solutes so when there's a high concentration of solutes or ions it will cause the water potential to be the other way around to have to be at a low a level okay so low water potential now that means the cell cell is very concentrated with the mineral ions and it has low water potential thus water will always diffuse from the area of high water potential to the area of low water potential also it will diffuse from the soil into the root hair cells by osmosis down the concentration gradient from the area of high water potential to area of low water potential high to low right so no energy is required for this process to occur okay so follow the steps one two three on and the notes here and this is the complete answer thirdly let's discuss an example of facilitated diffusion this is the absorption of fructose in the villas okay so fructose is a monosaccharide like glucose and fructose is transported into the epithelial cells of pillars by facilitated diffusion okay so let's find out how fructose is transported across the plasma membrane into the epithelial cells of the villus first of all what is available so if we look at the small intestine if you cut through the small intestine and get a cross section we will see that the surface of the small intestine has a lot of finger-like projections sticking out like this to increase the total surface area of the small intestine for absorption of the digested food substances right so let's look at one villus now the wall of the villas the outer wall here is made up of a layer of epithelial cells okay so these are the epithelial cells of the villas not virus huh villas right virus means the microorganism right not which can cause disease so villas the finger light projections now let's look at one epithelial cell of the villus it looks like this so this epithelial cell still has no also has tiny projections to further increase the surface area okay of the um epithelial cell now so let's say we look at one of these cells now let's say it's at the top here now the cell is facing the lumen of the small intestine which is the canal or the whole of the small intestine where there is a high concentration of fructose right why is there high concentration fructose because this fructose is the end product of digestion of carbohydrates one of the end products right so the concentration of fructose is higher in this intestinal lumen compared to the in compared to inside the epithelial cells right thus fructose will diffuser from the lumen into the epithelial cells but with the help of a transport protein okay which helps move the fructose molecules across the plasma membrane into the epithelial cells down the concentration gradient from the area of high concentration in the lumen to an area of lower concentration of fructose in the cell so no energy or atp is needed for this process to occur all right so we've discussed some examples of passive transport in living organisms now let's go on to active transport one common example of active transport is the absorption of mineral ions into root hair cells right not water absorption of mineral ions okay so this is also an spm past year question now how to explain the absorption of mineral ions into root hair cells by active transport okay so firstly we can say that the soil solution has a lower concentration of mineral ions such as calcium ions nitric ions magnesium ions just pick one so salt solution is the lower concentration of mineral ions compared to the cell set of the root hair cell okay so the cell set has already got a high concentration of mineral ions but it still wants to uh take in or it still wants to transport the mineral ions from the soil solution into the cell okay so the mineral ions such as calcium ions nitric ions magnesium ions are absorbed into the root hair cells by active transport against the concentration gradient because the mineral ions have to be transported from an area of low concentration of mineral ions into the cell which already has a high concentration of mineral ions from low to high okay from uh area of low concentration to area of high concentration like going uphill as you said huh all right it's an energy so this requires energy this requires energy from the cell for the active transport of mineral ions okay into the root hair cell so just follow the sequence here one two three to explain the absorption of mineral ions into the root hair cell by active transport lastly let's answer one question from the formative practice 3.3 on page 64 of the textbook okay so the first question which is not stated here i can refer to page 64 is why do hawkers spray water on their fruits and vegetables why do hawkers spray water on their fruits and vegetables so the reason why hawkers spray water on their fruits and vegetables is to prevent them from wilting right so these are the key words now the ones in red which you must write in your answer scripts right to get the marks now so other than that we have to explain uh what happens when we spray water on fruits and vegetables that are going to wilt right so water will diffuse into the vegetable and fruit cells by osmosis right because the water is hypotonic water the water is hypotonic to the cell set of the fruits and vegetable cells so water diffuses into the vegetable and fruit cells via osmosis and this will cause the and the water will be stored in the vacuoles and so the vacuums will expand then the cell cell in each vacuum pushes the cytoplasm and plasma membrane okay in the cell towards the cell wall so this will create uh pressure which we call tugger pressure when the vacuum pushes against the cytoplasm and plasma membrane and then against the cell wall so tugger pressure is created and this will cause the vegetable cells and fruit cells to become turgid again so the fruits and vegetables will look fresh right and then they can sell more easily now b second question is explain what happens when sugar is sprinkled on strawberries explain what happens when sugar is sprinkled on strawberries so the process that occurs when sugar is sprinkled on strawberries four marks is that the sugar solution will dissolve in some fluid and it will form a concentrated sugary fluid okay which becomes a concentrated sugar solution which becomes hypertonic compared to the cell set of the strawberry cells so that means the sugar solution is more concentrated right has a higher concentration of dissolved substances which is the sugar compared to the cell set of the strawberry cells so water will always diffuse from the hypotonic solution to the hypertonic solution so water will diffuse out of the strawberry cells okay from the cell set which is hypotonic into the sugary solution the sugar solution which is outside outside the the cells which is uh hypertonic the sugary solution is hypertonic so water diffuses out from the strawberry cells by osmosis and when the cells lose water the cells will become plasmalized and the cytoplasm and vacuoles in the cells will shrink okay so the strawberry tissues will lose support and then the whole strawberry will become soft okay so one tip one mark and please take note of the keywords right in the in the answer here okay now so here the cells become plasmalized so this is the key word and uh we can add the cytoplasm and vacuole string so this may be either one not either or plasma plus more lives or cytoplasm and vector string to get that one mark okay so take note of the words in red which are some of the key words all right so that's all for this lesson i hope that you have learned something from it please share like and subscribe and see you in the next video