there are lots of different mechanisms for putting things back into the bloodstream and for things to be removed through secretion so i'm just going to go through a few of them here you don't have to know for the exam any specific mechanism for moving any specific ion or molecule in or out okay but i do want you to know what the terms mean and you should already know this you should know you know facilitated diffusion and primary active transport you should know what that is and the two forms of secondary active transport and pinocytosis so facilitator diffusion is the only one here that is where you're going down your concentration gradient from high to low it does not require energy and you're going down the concentration gradient because it doesn't require energy because it's diffusion you're using a protein so the um diffusion is being facilitated or allowed to happen by a transport protein so you're going from low concentrations to high concentrations excuse me low concentrations primary active transport you're going against the gradient so you're going from high to low and to do that you need a pump you need to expend energy you're going against the concentration gradient and primary uses atp directly breaks the bond on atp uses the energy directly to fuel the pump move these down a little bit just to smush okay secondary active transport so all of these are using proteins to facilitate the movement of something across the membrane and remember we're talking here is the tubule the cells in the tubule and then here are the cells in the capillary so something has to go across the tubule into the interstitial space and then across into the capillary okay so you're going to you know if something is going back into the blood or if something's being secreted it has to go from the blood across those cells and then into the tubule system that way all right so secondary active transport this is anti-porters and symporters antiporters are proteins and they're going to use the energy so if something goes down its own concentration gradient like sodium moves into the cell it can create energy it's like riding your bike down a hill all right as soon as you open up a means for it to to get across it can you know it's going to move and it can generate energy now you can use that energy to push something else against its concentration gradient so antiporters things move in opposite direction okay so say sodium is going into the cell and it's pushing something out it's importers they both go in the same direction it could either be um into the cell or out of the cell if these don't sound familiar to you at all go back and review them okay i'm not going to ask you if glucose is tran is moved this way and this one's moving that way but you should know these these this was in the very beginning of your first semester and it's just a matter of reviewing them okay and then pinocytosis remember is a form of endocytosis called cell drinking which is used to bring in endocytosis used to bring in water droplets things like that dissolve solutes okay so those are some of the different transport mechanisms now to get back to the glucose glucose as it's being so you have glucose in the cell and glucose has to be i mean glucose in the tubule and glucose has to be put back into the blood because that's a very valuable fuel that's like gold okay we don't want to lose any of that but transporters only have so many binding sites you know if we're talking facilitated diffusion the um there's only one place where it can bind and so you move one of these guys at a time and if you you can't move another one until that one is on the other side okay so if here's our transport protein and here is the the spot where it binds glucose and so here's our glucose and it binds here until this guy drops that off on the other side you can't bind another glucose so we say that we have a transport maximum that it's like the number of seats on a bus right if you're riding on a bus or if you want to ride on a bus hold on a second okay if you want to ride on a bus and all the seats are full you either have to stand or you have to wait for the next bus and it's the same type of situation here and if all the transporters are are actively moving glucose out of your your tubule system back into the bloodstream and there's say a thousand glucose molecules and there's only 100 transporters you're going to lose a lot because it's not going to sit there and wait for you for it to come back this is flowing it's sort of like an assembly line you know like one of those belts on an assembly line kind of like i always visualize with this uh lucy and ethel if you've ever seen that it's hilarious um on the i love lucy show with the candy going by and they're trying to wrap the candy up and they can't do it they can't do it quickly enough and so they start stuffing it in their hats and sticking it in their pockets putting it in their mouth and then their boss thinks they're doing such a good job that she speeds up the belt and then it just you know it's very funny anyway that's kind of what this is like once all the seats are taken you can't can't do any more so the term transport maximum refers to maximum number of molecules you can move and if your blood glucose is high you exceed the transport maximum and glucose stays in the urine and that's called glucosauria and that's a sign of diabetes um because you shouldn't be losing glucose the thing is their cells are not taking up glucose for whatever reason type one type two and because they're not taking up glucose the blood levels of glucose are really high and they stay high and then you end up losing a lot of it in the urine okay now as far as how we're going to move water um water is moved via osmosis most water actually let me go to another page most water is going to be transported and for this we actually have two types of water transport we have facultative water reabsorption so we're talking about putting water back into the blood vessel and we also have so we have facultative water reabsorption and we also have obligatory water reabsorption facultative um or let me just talk about obligatory first obligatory water is obliged to follow salt where salt goes water follows okay so basically and this is a lot of what the fluid electrolyte balance chapter is about where salt goes water follows so balance of the different ions in your body is going to kind of dictate fluid balance as well okay so if sodium is being transported back into the blood water is going to follow it so where salco's water follows obligatory water reabsorption facultative happens in cells called principal cells okay now facultative water reabsorption and the way i remember it i always remember those two go together i think a faculty and a principal even though it's not really faculty it's facultative the facultative water reabsorption involves the principal cells and facultative water reabsorption is water reabsorption that occurs because of adh antidiuretic hormone acts on these guys inserts protein i should say water transport proteins called the aquaporins and um so facultative water reabsorption happens because of the antidiuretic hormone obligatory water reabsorption is the main way all right and that's the osmosis water is obliged to follow salt or sulcus water follows okay and so this is how water is moved uh why don't we take a five minute break it's 7 45 now come back at 7 50. i know it's not a lot but we still have a whole lot to cover so uh take a five minute break and i will see you all in a few minutes