[Applause] hi everybody and welcome back to miss Angela's biology class I am Miss angler in today's video we are going to do enzymes we're going to look at the different kinds of enzymes how they work and how best to explain enzyme action when we have to write a test or an exam not only are we going to look at enzymes in their properties but we're also going to focus on what affects their ability to do their job and so we're going to look at things like pH and temperature as well now what's really important about enzymes before we get into this video is that I want you to always think of enzymes being like the golden substance in life sciences or biology they are the substance that runs everything within any organism and without them organisms wouldn't be able to breathe repair reproduce anything um and so I want you to keep them in the back of your mind that enzymes run every process and system that we see in any cell now if you are new here don't forget to give this video a thumbs up and make sure you're subscribed with your notifications turned on because I post every Tuesday and Thursday so let's get into the basics about enzymes and very quickly and very briefly I just need to explain the two major categories that enzymes fall into and then from there I'm going to explain a little bit more about a physical enzyme itself so first things first I need you to know that enzymes actually come into categories that we can see in these pictures how they're going to elaborate very quickly now the first category that enzymes come in is what we call extracellular enzymes essentially what those are is enzymes that are created in these structures over here called vesicles which you may know about are like really small vacuoles and enzymes are made inside these little vesicles they move to the edge of a cell's membrane and it secretes out the enzyme and so we call them extracellular enzymes because the enzymes leave the cell to be used outside a really good example of an enzyme that would do this would be something like salivary amylase so the starch enzyme in your mouth and that's because the enzyme is made inside a cell and then secreted outside of the cell which you experience you know in your saliva now on the other hand the other kind of enzyme we see is intercellular enzymes the difference is these enzymes don't leave the cell they are used inside the cell and for many reasons you may find you will use enzymes inside the cell something like for example the mitochondria needs intracellular enzymes to function but we have a little example here where you will see there's like a little food vacuole that forms let's say for example this is a protist um and this particular cell needs to break down this food that it's absorbed through its cell membrane along comes another organelle called a lysosome and they combine together as you can see they fuse their membranes and basically the lysosome comes along with digestive enzymes and it helps you digest this like food that you've absorbed through the membrane now we wouldn't see this kind of thing in like humans and multicellular organisms you would see this in simple single-celled organisms but I just want to bring your attention back to this lysosome thing this lysosome is a specialized vesicle which you actually remember this word from earlier in the video a vesicle um lysosomes the word lice or lysis it means to cut and so literally if a cell goes through lysis it's cutting itself up into pieces and dying so lysosomes are also really important because they have the cells that cause cell death because at some point a cell needs to die especially if it is sick infected or damaged so now that we have an understanding of where we can locate these enzymes now we need to think about their properties so what makes an enzyme an enzyme so first things first um we need to look at about a list now this list that I have here for you is going to be great for exams and tests because this is exactly what they're going to ask they're going to say like name two or three properties of enzymes so first things first enzymes are globular and what that means is there's three dimensional like a blob and these little pictures alongside you are actually really great because that is sometimes what enzymes look like they look like these clumpy Blobs of protein which brings me to the next Point enzymes are protein and that's a really important thing to keep in mind as we progress and we look at what affects enzymes and your ability to do their job the next thing is that enzymes are reusable so they can be used over and over and over and over again which is great because you'll need a small amount of them enzymes are sensitive to pH and temperature which actually links back to the point about proteins all proteins are sensitive to pH and temperature which means that if you change the pH or the temperature you might run the risk of denaturing it in other words changing its shape speaking of shape let's talk about what it means to be substrate specific which literally means a enzyme is shaped a certain way because it must match the substrate or the substance it's going to work upon so let's say hypothetically the enzyme is a circle shape the substrate must also be a circle it cannot work on a square and that brings me to this little picture alongside here sort of illustrating what the properties of enzymes can be used for if we want to for example break down carbohydrates we will notice that carbohydrates are stacked together like this in a very complex model we then apply our enzyme which we see in the middle here and that allows us to then break a very complex molecule like a carbohydrate into simple sugars and you can see they're all separate and free here and likewise if we want to break down proteins or fats they have a very specific enzyme that will do that and as you can see the names are given of those enzymes now depending on your school you may need to know some of these names right now you definitely will need to know their names for grade 11. so don't think that this is the last time you're going to see them so let's now tackle the most let's say difficult thing we need to know about this topic right how to explain a reaction how to explain how an enzyme works so remember enzymes are there for chemical reactions and processes and what's important to know is that without enzymes a reaction would be really slow and so that's why we also call them a catalyst and you may have heard this word before but a catalyst is another word for an enzyme and basically it means it speeds up reactions so without enzymes most chemical reactions would be so slow that the organism would actually die now what we have here in this picture is an illustration of how a reaction with an enzyme can occur and I'm going to walk you through how I would explain it in any test or an exam so first things first um our enzymes right they are going to attract a specific substrate so the substrate is attracted to a specific enzyme and we know that because if we actually look at the picture here you will see the shape of the enzyme that matches the substrate that's moving in and that brings me to my second point the active site which is that little Dent must match the substrate which it does in this picture now the Second Step here is the enzyme provides the what we call activation energy to begin either the anabolic or catabolic process now what does anabolic or catabolic mean well anabolic means that we want to build something okay so that's a building up reaction catabolic on the other hand is a breaking down reaction and actually that's what you can see in the picture alongside here this is actually a catabolic reaction I'll show you how the anabolic one would work soon but it brings us to our final step the product or products because there might be more than one leave the active site unchanged and that's important because remember enzymes are reusable so we can use them again and again and again and now the enzyme can be used for another reaction and this is why we also liken it to a lock and key maybe your notes has said that before that enzymes are like locks and keys they must match number one and number two they can be used over and over again now as I just mentioned now by the way this is a catabolic reaction So reading it from left to right that is a quite catabolic reaction but actually the anabolic reaction is just in the opposite direction we would take two substrates we wouldn't call them products because we're starting on this side we give them their activation energy and we would end up with one product on the other side so this is actually a reaction that we can read from left to right or right to left now if you're thinking to yourself well who decides whether we need more or less of a substance that is based on the needs of that particular organism and so for example if we need more sugar we will break down a carbohydrate but if we have enough sugar we will build it back into a complex carb and store it away for later and that is all maintained by homeostasis and hormones in the body Now we move on to factors affecting enzymes and earlier on I mentioned to you that enzymes or proteins and proteins are really sensitive to pH and to temperature I want to put a little disclaimer here and say that every enzyme requires a specific pH that is unique to it but also enzymes function better at certain temperatures again it's specific to the enzyme so I'm going to speak in this example in a general way but you will also learn about some very specific enzymes that need very specific conditions so looking at the left hand graph we are dealing with ph and for the most part enzymes have an Optimum rate of reaction which we can actually see as the peak of this graph that is the optimum and what we notice here is as the pH increases the rate of reaction increases however once we go past Optimum as the pH increases so does the reaction rate decrease and this is something that you would need to be able to describe now what is really important about describing pH is that no matter whether you go up or down in PH you always end up denaturing the enzyme now what is denaturing the enzyme essentially denaturing means that you have changed the shape of the enzyme and the golden rule of Life Sciences is you if you have changed the shape you have changed the function and that is a big deal because if an enzyme is a different shape it will no longer match with its substrate and you can't use it anymore and so if enzymes are the golden substance in life sciences the golden rule is everything has a shape because of what it does its structure equals its function its shape equals its function now if we look temperature again you notice a very similar kind of curve you will see we've got the optimum temperature over here and again as temperatures increase so does the rate of reaction however it's a little bit sharper down you'll notice as temperatures increase the rate of reaction dramatically decreases but I actually want to stress this uh explanation quite a lot now pH it doesn't matter if you go up or down in PH it will denature the enzyme in temperature however cold environments do not denature instead they become inactive the enzymes are like Frozen in time they become inactive however if they are warmed up they can return to functioning heat however or hot temperatures they lead to denaturing and the example I use in my classroom is cooking an egg you can't uncook an egg once an egg is cooked it's cooked okay it's stuck in that state and that's why heat is unfixable it's undoable you can't get rid of it once it's changed the shape of the protein however I could freeze egg whites or raw eggs and they would stay as is until I defrost them and then cook them and so that's sort of a way to think of it and remember it now I also want to just further elaborate on what it means to change the shape and change the function and I'm going to show you now another picture to sort of illustrate that this is an enzyme that has changed its shape due to its pH so I'm going to put it on the pH uh side over here and what you'll notice is originally the substrate fitted in quite well in the active site but because the pH went from Optimum to not Optimum so it went up it increased you'll see that the shape of the active site changed and now the substrate can no longer fit and that's what happens when we say denaturing now as always I like to finish off my lessons with the terminology recap you can use these words to check your understanding to make sure you know how to use them correctly you should also be using these words in your answers and tests and exams and lastly you can use these to create flashcards because terminology is really important in life sciences so starting off in the beginning we spoke about extracellular and intracellular enzymes that's basically where we find them inside a cell or outside a cell and then we spoke about their properties and first things first we spoke about the fact that enzymes are catalysts they speed up reactions and they provide energy to do that and those reactions can be anabolic which means building up or catabolic which means breaking down now specifically speaking about those reactions we always speak about a substance or a substrate and it's going to be acted upon and the enzyme is going to take that substrate they're going to link in the active site of the enzyme and it's going to provide it activation energy and we're going to end up with a a product of some kind now enzymes are proteins which means they're sensitive to pH and temperature and because of that they are able to denature and once you've denatured a protein it cannot be undone just like I mentioned you can't uncook an egg so once it's changed its shape it's changed its function now if you like this video don't forget to give it a thumbs up and make sure you're subscribed with your notifications turned on because I post every Tuesday and Thursday for grade tens to twelves and I will see you all again soon bye