hi everyone and welcome to learn a novel biology for free with mr. ik in today's session we'll be looking at two types of transport across membrane active transport and Co transport so if you aren't already subscribed click below to subscribe and if you do like this video today then give it a thumbs up get yourself some pen and paper if you want to make notes as you go pause it rewind go at your own pace so I'm gonna start with a recap from some of the knowledge email from GCSE but also earlier on within this topic at a-level so you've got three diagrams here looking at transport across membranes first thing is nice and easy to get into it but in the difference between the diagrams and then using that knowledge to come up with what types of transport each of these three are so the key differences are they are all across a membrane but the first one it's going down its concentration gradient without a protein second it's still going the molecules are moving down their concentration gradients but this time it's through a protein and lastly the molecules are going against the concentration gradient through a protein but also with energy in the form of ATP so naming them so the first one is simple diffusion second facilitated diffusion and lastly active transport and that's the one that we can be focusing on today so active transport then at GCSE you learnt that it's the movement of substances from an area of low concentration it's an area of higher concentration and that has to go through a carrier protein and because it's going up against its concentration gradient it requires energy and that's in the form of ATP now a bit more detail at a level starting off we have a look at this diagram we've got our transport proteins but they're always going to be carrier proteins and these the ones where they will attach one side and then they carried through to the other and those proteins span across B with of the membrane the soda Mart which is the example that we're using in this case are going to attach to that carrier protein because the shape of the sodium ions is complementary to a receptor site on the carrier protein say molecules that are complementary to the receptor site are the only molecules that can attach to this particular carrier protein but within a membrane there'll be lots of different carrier proteins for different molecules to be able to attach to so that's what's happening in step 2 here step 3 the ATP within your cell will attach to the carrier protein and immediately after attaching is hydrolyzed into ADP so adenosine diphosphate and the third phosphate remains attached to that carrier protein and because that phosphate group is attached it causes the carrier protein to slightly change shape so it's altering its unique 3d tertiary structure a bit of a recap on protein structures just click up here if you need to see the protein structure video but as that carrier protein changes shape it causes the release of the sodium ions to the other side of the cell the last thing is the phosphate ion will be released and when it does get released the carrier protein is restored to its original shape so that is the extra details of our active transport so you can actually see how the carrier proteins involved the slight changes in its tertiary structure based on the binding of different molecules and how the ATP is literally used so it's that hydrolysis of ATP to enable the phosphate group to attach to the carrier protein so of course the change which releases the sodium ions so our example of active transport that we're going to focus on is Co transport and the example on AQA specification that you need to know is Co transport of glucose or it's the same for me in assets as well k transport of glucose with sodium ions in the ileum so within the small intestines looking at how glucose is absorbed into the blood so the reason then that acts of transport or this co transport is required for this step is the concentration of sodium ions within the epithelial cell and this is the layer of cells that are lining the walls of the small intestine so the ileum that those epithelial cells usually have a really high concentration of glucose so that means as the digested food is flowing through the lumen of your small intestines or the ileum you do not have that high to low concentration gradient to enable facilitated diffusion so instead the absorption of glucose has to be through active transport and to enable it to get glucose to go against its concentration gradient and the type of active transport is K transport so let's have a look at each step in this process so step one we're going to start at this point in the diagram and just go back on just to show you we're looking at the blue section is representing the lumen of the ileum so that's at the inside of the tube which is your small intestines then we're looking at the epithelial cell so these are the layers of cells that line the walls of the intestines and then we've got the capillary which lies right next epic video cells and the blood within it so step one is if we look at is just here and we have a carrier protein which is enabling sodium ions which is the dark blue to be actively transported from epithelial cell into the blood within the capillary now this is actually also co transport because as that happens a potassium ion is transported from the blood into the epithelial cell but actually that extra detail isn't focused on within the specification you need to know so the first step is sodium ions from the epithelial cell actively transported into the blood and this stage is exactly what we just looked at in terms of active transports the ATP attaches hydrolyzes and that enables the sodium ions to move from the cell into the blood the reason that part has to happen is we now have a much lower sodium ion concentration within the epithelial cell compared to the lumen of the ileum and that means these stadium ions within the digested food in the lumen of the ileum can move by facilitated diffusion into the cell down their concentration gradient so that will then happen the protein that the sodium ions diffuse through is actually a CO transporter protein and what that means is two different molecules attached before either of them are transported to the other side so the sodium ions will attach to their complementary shape receptor that then enables glucose molecules to attach once the glucose attaches that means the sodium can be released on the other side and that then enables the glucose to be released on the other side so they are transported together which is why it's code transports so now within the epithelial cell we'll get a buildup of glucose and this code transport enabled glucose to be moved from the lumen against its concentration gradient into the epithelial cells so that high concentration of glucose within the epithelial cell enables the glucose to move down its concentration gradient from the epithelial cell into the blood in the capillary and that's by facilitated diffusion so a couple of extra points the first one is the reason blood doesn't have and this buildup of glucose molecules as they're being absorbed and that's because within the capillary the blood is constantly flowing so as soon as this glucose molecule is absorbed into the blood the Bloods flowing and carries it away so this flowing blood is what Taine's the concentration gradient of glucose between the epithelial cell and the capillary second things to point out is on this epithelial cell these yellow lumps here are actually meant to be micro villi and that is to increase the surface area of this epithelial cell and although I've only shown one of these code transporter proteins for sodium and glucose you'd actually have lots of these code transporter proteins within the membrane of this epithelial cell and the more of these code transporter proteins you have the more sodium and glucose can be absorbed so by having these micro villi you get this highly folded membrane and therefore lots of code transporter proteins are embedded within the membrane and that gives the maximum absorption of glucose so that's it for K transport and active transports so just in summary first of all both active transport and code transport are ways to move molecules across a membrane code transport is a type of active transport so it will always involve ATP we went through active transports we said it's always through a carrier protein and it's possible because ATP is hydrolyzed to ADP MPI and it's the attachment of the pie which is inorganic phosphate which causes the carrier protein to change shape and release molecules to the other side of the cell membrane lastly then K transport is how glucose but also amino acids are absorbed from the lumen of the ileum into the epithelial cells of ileum and then finally into the bloodstream so that's it for active transport and K transports head over to miss Esther accom 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