all right so today we're going to be doing an enzyme lab we're just starting our enzyme unit so some of this will be kind of new information and you'll get to kind of see how things work before we jump into all of our details what we'll be using today is yeast which is what you could just grab at the grocery store this kind of straight from the grocery store and then also some hydrogen peroxide which you would also just get at like you know cvs or something this is only three percent hydrogen peroxide it's the stuff you would put like on a cut if you had one so it's not super strong but it's definitely going to give us the reaction that we're looking for today so some background information that you need to know is that in yeast there is an enzyme called catalase and it works on the substrate of hydrogen peroxide and when the enzyme works on hydrogen peroxide it actually breaks it up into water and oxygen and what we know about oxygen is that oxygen is a gas and so when that gets produced inside of a liquid it'll actually kind of make these bubbles which should cause the thing that is in yeast which is going to be filter paper in this case to actually rise to the top of our liquid so we'll be able to kind of test the fact that this enzyme is working by seeing how quickly our filter paper that is dipped in the yeast rises to the top what you need to know to kind of fill in your introductory information is that we'll be using four different concentrations of hydrogen peroxide today so we have three percent hydrogen peroxide which is the one that came straight out of the bottle but i moved it over so that it kind of looks the same next we have one and a half percent hydrogen peroxide that we'll be testing then we have 0.75 hydrogen peroxide you're probably sensing a pattern i just cut them in half and finally 0.375 percent so you're going to want to fill those in on your table where it says that there's four different solutions um that you're using fill in those percentages that i just gave you and then take a minute to read the background information and fill in your pre-lab questions and then we'll come back and do the procedure together welcome back now we're going to start our procedure just so you guys know some background about what i've already done for some of our lab setup i did already make our yeast solution because that does need to sit for maybe five minutes or so to kind of activate the yeast because dry yeast is kind of dehydrated and so you put it in some water to kind of activate it get those enzymes going again i've also already pre-filled many of our test tubes that we'll be using so these are 15 milliliter test tubes and i measured in 10 milliliters into each of them of the appropriate solution so you can see here i labeled them you should always label your test tubes when you're doing a lab so here i labeled this one as three percent this is a three percent solution and i labeled it as number one so this will be my first trial i'll show you guys kind of how i did that i have one test tube that i left empty so what i'm gonna do is get my appropriate solution that matches my label so three percent and my three percent solution and i'm going to grab this pipette so maybe you've heard the word pipette before and maybe you've heard the word micropipette before micropipettes are much smaller and these are obviously the larger pipettes for larger volumes so we want 10 milliliters so i grabbed one of the larger ones because it'll be much more efficient so all i have to do is put the pipette into my solution and then i kind of twist this knob up here and that kind of sucks up the liquid and so i'm going to make sure that i grab 10 milliliters of my solution there we go and then i can go the opposite direction with the kind of scrolling circle up here and get all of that into my test tube so pretty simple this is how you would measure it out if you needed to in class any kind of thing that you want precise amounts for this lab it didn't actually really matter how much i put in but it's definitely important that we have consistency because what we're going to be doing is timing how long it takes for the filter paper to rise to the top of the liquid and so if we had all different levels those times would not really be able to be compared to one another so i wanted to make sure that we had the same amount in all of our test tubes our next step in our procedure is to cut out our filter paper discs i've cut out a couple for you but i just want you to see kind of how i did it so i grabbed a piece of filter paper and a hole punch pretty simple and i just punch out a couple of these filter paper disks pretty easy the next step in your procedure tells you to kind of dip the discs into the yeast for about five seconds or so and then let it kind of sit on the paper towel to let extra liquid kind of drip off of it so what i'll do is i'll go ahead and i'll dip all 12 of my disks in and then i'll let them sit and we'll get started with our actual trials i made this yeast solution pretty concentrated so that i know that it's definitely getting enough yeast on it so if you look at your procedure it said like one teaspoon for 200 milliliters of water or something like that and it doesn't need to be that precise oh i dropped one i'm not even going to bother grabbing that as long as you know you're getting yeast onto your filter paper you should be all set you've probably noticed is that everything in this lab is something that you could grab at the grocery store or the convenience store so you could definitely do this lab at home it is safe it's just you know the general hydrogen peroxide and yeast that you would get but i didn't want to force you to go buy those things so i'll do it for you this is the boring part when you're getting yeast onto the filter paper so far i have four because i dropped one so i apologize for the fact that you now have to watch me do this what we'll be doing once i get all of my filter paper in yeast is putting them on the lids of my test tubes so this makes it so that i can kind of control when the hydrogen peroxide actually touches the yeast spheres if i put it on the lid of the test tube then what i'll end up doing is i'll flip my test tube over and when i flip the test tube over that's when the hydrogen peroxide will actually kind of hit the filter paper and that's when i can assume that's when the reaction is starting if i was kind of trying to place the filter paper at the bottom of the test tube it might be kind of difficult to know when the reaction is starting the timing aspect of it would become a little bit trickier so this should be pretty easy and that will put it in the lid i'll close it up since the filter paper is wet it'll stick to the lid and then i can just invert my test tube and then i'll start my timer and i will stop my timer when my filter paper gets to the top of my liquid i have not been counting 13. okay so we're gonna start with the three percent solution so when you're filling in your data table make sure you start with the three percent and we're going to do three trials of all of our concentrations so we'll do three trials for the three percent three for the one and a half so on and so forth so i'm going to grab one of my filter papers i'm going to put it on the lid make sure that it sticks hopefully that sticks let's see oh it's definitely not sticking hang on let me try another one i need to re-dip this in the yeast we'll see all right i think this should be okay so i'm going to put the lid on it's kind of stuck to the lid right now i'm going to flip my test tube over and i'm going to start my timer at the same time and i'm watching for my filter paper to rise to the top there it goes you might not be able to see this that's okay all right and it has reached the top oh my gosh 12 seconds exactly look at that so for three percent the first trial was exactly 12 seconds now we'll do our next one as these kind of dry off it becomes a little bit harder to make sure they stick to the lid so i might have to kind of dump them in the yeast again at some point we'll see oh no we're okay we're just gonna use a new one because it almost fell in all right trial two for the three percent this one's going way faster i probably put more yeast on it 7.62 seconds yeah so these are mostly drying out so i think what i'm going to do is i'm going to kind of dip a couple of them in the yeast again just to get them a little bit wet so that they stick to my lid and i'll blot them dry a little bit just so that they're not covered in yeast but this should help them to stick better so this is trial three for my three percent reset my timer and flip here it goes and it's at the top wow 12 seconds again pretty consistent so the middle one was a little bit faster that's why we do three trials and we'll kind of average them all together once we get to that point so you're probably getting an idea for how this procedure works and now we are doing a lower concentration of hydrogen peroxide so what i want you to think about is in theory the enzyme concentration should be the same between all of my trials because that's what the yeast is but i'm changing the concentration of the substrate the thing that's getting broken down and as i get less and less concentrated of substrate i want you to think about what might happen to the time all right so we're going to do trial one of the one and a half percent so i have less substrate less material that can be broken down by this enzyme so i want you to think about should it take more or less time for those gas levels to be produced and it reached the top at 14.41 for this one all right trial two for the one and a half percent so we saw in the first trial that it took a little bit longer than the three percent think about if this makes sense to you and what you might expect to happen as we get smaller and smaller in concentration 14.8 while you're kind of waiting for me to do this and thinking about it i would also like you to think about what might you be able to do to make this reaction go faster so we know that as our concentration is going down it seems to be taking a little bit longer i don't know maybe i don't actually want to have to wait 30 seconds or something for this to happen so what concentrations might help me to kind of speed up this process so i have 14.14 so we've done our two highest concentrations so kind of make a hypothesis in your head right now about what do you think is going to happen to the time as i do my lower concentrations and maybe in your head right now you're thinking this is about to get pretty boring because it's going to take longer maybe i should have started with this lower concentrations first sorry all right so we're on trial one of my 0.75 hydrogen peroxide now since this is like an actual experiment right there's always room for error something could happen we might have a fluke in one of our trials that's okay that's why we take an average of all three of my trials all right 18.39 that's not too bad right so we're on the second trial of the 0.75 percent i'm going to flip it over start my timer and see how long it takes so i need to wait for it to rise all the way at top when i flip it sometimes it like moves around a little bit that's just because of the fact that i'm like flipping it into liquid so it kind of like pops up a little bit and then comes back down um but i'm waiting for it to actually like rise to the top because of the bubbles so this one was 16.78 and my final trial of the 0.75 see how long this one takes reset my timer there it goes and 16 seconds on the dots so this might remind you a little bit of a lab that you might have done in general bio with photosynthesis or you had little circles of spinach leaves and you had them in baking soda and you saw those rise the top two also because of the production of gas actually also because of the production of oxygen gas so that's kind of an interesting little connection here right we use the production of gas a lot to kind of measure how well a reaction is working or how quickly a reaction's working because it's one of the easiest things to actually see right we can see gas bubbles being produced we can't really see other a lot of other things being produced all right we are now on to our final concentration so that's the 0.375 our lowest concentration and we are on trial one so hopefully you have an idea that this is probably going to take a little bit longer than the other ones we'll see what actually happens it seems to be just kind of sitting at the bottom right now it is quite possible too that you can eventually reach a concentration where maybe the reaction doesn't happen at all because there's just not enough to produce enough oxygen we might be there we'll give it some time though this is taking a while huh so i will say in the past when i've done this lab this one doesn't typically take this long but um there's some like kind of room for error there and some things that we could think about i'm starting to see oxygen bubbles now they're like just forming here it goes so we can kind of talk about in class why maybe this one is taking so much longer um but wow a minute and 24 seconds just over a minute 24 seconds there's quite some time compared to our other ones we'll see if it does the same thing on our second trial so you can see the oxygen actually being produced when you're like looking at it as close as i am and what we saw with the three percent was that the oxygen bubble started getting produced almost immediately um and with this one right now when i'm looking at it it just looks like my filter paper is just sitting in water essentially i don't see any gas bubbles i would have no idea that there was yeast on this um there's just not much happening and it took until almost a minute on the last trial for us to even get any oxygen bubbles produced which is pretty long if you compare that to the rest of our trials um let me see i'm starting to see a few a couple oxygen bubbles and we're at 43 seconds so definitely a lot longer and so we're going to talk about kind of why this is happening and what these different concentrations of substrate might mean in terms of like how effective my enzyme is we'll also time talk about what other things we could do to change the rate of the reaction what would happen if i put a ton of yeast on here or barely any yeast oh here it goes all right a minute 14 a little over a minute 14. there are definitely other things that you could kind of adjust for this lab to test we only are testing different concentrations of hydrogen peroxide but you could also change the um well i grabbed the wrong food you could also change the temperature of things um you could kind of see if any other things would cause a reaction in the other types of substrates they would hopefully only work with the correct enzyme but you could definitely test other things all right here's our last one so keep in mind that we're only doing concentration on this one right so we change the concentration and we change the concentration only of the substrate when you do an experiment it's really important that you kind of only change one thing at a time that way any differences that you do see you can link directly to that thing so any changes that we see in the time here is going to be directly linked to the fact that we changed the percentage of the substrate and nothing else we don't want to change two or three variables at once because then who knows maybe it's because there's more yeast or maybe it's because the temperature change you don't want to be moving around lots of different things at once so it's really important that you only change one thing at a time this one seems to be moving a little bit faster 57 seconds so a little over 57 seconds so write that value down on your table and now you should have 12 different values written on your table you should have three for each of the concentrations you'll find on your data table that you're going to be doing a couple of calculations you're going to be having to average the time and then you're going to figure out what the rate of the reaction is it's laid out for you on how to do that calculation next you'll be creating a graph and you're going to graph how the rate of the reaction changes as we change the concentration of the substrate and then you're going to be writing me kind of a conclusion paragraph about how these changes um happened what did we actually manipulate in the lab and then also what does that mean so why does that happen or what are some other things we could do in the future future experiments to test similar ideas with enzymes so go ahead and kind of make sure you have all your data written down you can go back in the video if you need to get any of those values again and then start on your calculations and then jump into your graph and your conclusion thanks