Essential Biology for GAMSAT Preparation

Hey everyone, welcome back. My name is Jesse. I am a tutor in Melbourne and I also make GAMSAT videos and crash course videos like this to help people prepare for section 3 of the GAMSAT science section. Today what we're going to do is actually go through the very last of the biology crash course. series which has happened very very quickly this will be the fourth installment over the course of just four weeks basically and I've already done these for chemistry and physics as well and we kind of kept them down to about three and a half to four hours or so to really prove that you can condense the theory that you actually require for the test into a relatively short amount of content. Of course this is stripped back, it is just the bare essentials and realistically the highest yield stuff. There may be little bits and pieces that you might find in a question but has it been repeated? No. So we're really looking at people with a non-science background can kind of go through these videos, brush up on all the skills so that they know what they're actually supposed to be studying. studying for because the world of chemistry physics and biology is very very broad and there's really not that many things that GAMSAT's really requiring of people we're seeing a new structure that they're definitely introducing concepts to you what we focus on in this is getting you familiar with those concepts so that you're not relying on learning information at the same time that you apply it if you would go in blindly into the GAMSAT with no prior knowledge then it would be very tricky to actually navigate the information and every now and then we do find that they do test some prior knowledge but for the most part it is a reasoning test you want to be focused though on actually applying the reasoning not any kind of learning so with the bio one we know that it's much much less content based for sure compared to something like say chemistry and so with this series it's a little bit different in that we are looking at familiarity with the words understanding how cells function understanding how systems function so that when you go into the actual information you kind of have those basic assumptions under your belt and as well as that you're not going to be thrown or phased by any of the wording that's used. So with today's one anyway it's a bit of a mishmash of topics really. We've gone through and themed all the previous ones but today's one is really just a bit of a mishmash of topics that are kind of left over that didn't really fit in anywhere perfectly. I figured that would happen, bio is a pretty big topic and so we're going to go through a bit of a mix of things. We're going to start with gene expression which kind of links into a bit of the genetics from the second one. uh from the first one actually that was then we did cell structure second then we're going to go through enzyme activity and how enzymes function as well because they seem to come up a lot in gamsat questions we want to be familiar with those then we're going to go through how to read hormonal and neural maps as well in terms of cell signaling and excitation and inhibition or stimulation and inhibition and then finally we're going to end on some metabolism and photosynthesis because again it's a little bit more theory based but we see that some assumptions and knowledge in this can be helpful in GAMSAT as well. So I'm going to try and keep it relatively short. Hopefully we're going to aim for about 40 minutes or so to get this one knocked out and then you'll be on your way to answering questions. All right so the first thing that we're going to do is go through gene expression and what this really is. This is a very very useful topic because although it may not always be assessed in terms of just translating say the nucleotide base sequence code backwards and forwards, it is really important to understand the basics of what gene expression is because it underpins a lot of the questions relating to genetics and you can extrapolate from here so the first thing is what is it it's really just the process of how we take dna into a final protein product right and there's two key steps i'm going to leave out there is a third step but i'm going to leave that one out because i don't see it as relevant to gamsat i'll mention it when we come up to it so that you can research it if you want to but i don't think it's all that useful the first one is here we convert DNA into mRNA and this process that takes us through this is transcription. And so we'll look at that first that's going to be step one. Now along the way here we technically do modify the mRNA and that's the step that I'm going to leave out because if it gets thrown in they will introduce any key facts that you need for the question and you'd probably be fine to work with the information. given. I don't think it's worth knowing it. It's a bit too technical and a bit too theoretical. The second step then takes us from mRNA into polypeptide, or really just a sequence of amino acids that can fold into a protein. So this is going to be translation. and that will be our step two that we'll go through. So starting off with transcription, I'm just going to zoom in here. We start with our DNA compound. Yeah, this will be our DNA. Now really DNA is a very very long long molecule, but along the way sections of it will be genes and we've talked about this in the first of the BioCrash course series. And so we've now isolated one of these genes, we're just looking at part of it, and it's obviously very very short. Most genes are going to be in the hundreds to even thousands of nucleotides long, we're only drawing 10ish or so, so obviously a much simplified version of it. And so I'll point out we've mentioned these before, we have 3 and 5 prime end, these are just ways to identify which end of the compound we're talking about. It relates a little bit to the structure, the 5 prime end has a free phosphate and the 3 prime end has a free sugar. On its end, it's pretty unlikely for that to be all that relevant to a GAMSAT question though. But I put these in so that we can kind of distinguish where we are. And so on one end, we're going to have this red circle here, which is going to be an enzyme called RNA polymerase. Now, again, you don't have to memorize names or anything like that. I'm just going to reference them so that you're familiar with the words, so that if they do talk about that, you already have heard the word before. You don't need to go memorizing what RNA polymerase is. how it functions and all the rest of it, they will guide you through that in the stem. We just want to understand what the process here is. So this enzyme will actually attach to one of the two strands, in this case this bottom one, and what it's going to do is it's going to run along the DNA and read it and then lay down complementary RNA nucleotides, which we talked about. So remember that the code is A to T, G to C and vice versa. But because we're dealing with mRNA, we don't actually have thiamine in there. We have uracil instead, uracil. And so this will be the U. And so if I make up, for example, a nice simple one, let's do T-A-C, and then we'll just make up stuff like G-C-A-T-T-A-C, or G. There we go. So complementary to that, we'll do that on the other side, and I might just color code this, would have been... A, T, G, C, and then to C would it be G, T, A, A, T, C, like that, right? So that's all pretty familiar. And so as the RNA polymerase runs along, what it's going to do is lay down complementary mRNA. So what I might do here, just to make life a little bit easier for myself, is if I can grab it all, just about. I'm just going to bring that up a little bit to create a bit of space. And... Here we go. Cool. Alright, and so as it runs along, let's say it's already kind of started its way along, and opposite to T, it would have laid down an A. Opposite to A, it would have laid down a U, and then opposite to C, it would have laid down a G, like this. So you get A, U, G, and it's going to keep going, right? So if it continues to slide along, then next up it would see G, and so it'll put down a C, and so on like this, right? there then AAU and oh see just like that and this here is going to be our mRNA molecule like that. Now you might notice a pattern right of course it's complementary to the bottom strand but it's also effectively identical to the top strand that got kicked out of the way right in the process so So the reason why as well, I forgot to mention, it bubbles out like this just so that it can access the DNA. But that bubble will run along and reclose behind it. So I've not really drawn it correctly because... Further down here, by the time it reaches this point, the bubble will have opened there to access the DNA. But I can't really animate it too well with a diagram. But I would recommend I'll link below as well some YouTube videos that do a really good job of showing that animation much better than I can do here. So you can watch those as well. The other thing that you can watch is if you go to like my super, super old videos, although that was only like four months ago. I started this channel really just making videos for my high school students. And so for my buyers. students i put together a three-part series going through transcription modification and translation if you want to watch those i'll link those below as well actually that'll probably be easier you can watch those they're in a lot more detail so you definitely wouldn't need to know them in quite the same detail because that's for my vce students but um in it i have a pretty good animation of where i i drew rna polymerase on my finger and used an analogy of a um a resealable sandwich bag for this particular thing that might be helpful so watch that one as well you but once it gets to the end everything kind of drops off and so we end up with this strand here and so the mRNA you can see is actually completely identical to this purple strand all the way along the only difference is that where we have T's we should have U's and in fact I made a slight error there that should be a U because because this is mRNA whereas this is just DNA like that and so this thing creates a little bit of naming structure which you want to be familiar with because they will probably use it if they go into this topic and that is that the bottom strand here because it's being read by the RNA polymerase then it's acting as a template so it's often called the template strand and so therefore the other strand of DNA would then be the non template strand like that. Annoyingly though there's a second naming system and it flips what is non. So as well as that you'll notice that the top strand the non-template strand is also identical to the mRNA i.e. it codes for the mRNA. So this is often referred to as the code strand and because the bottom strand is opposite to it it's often referred to as the non-coding strand. So there are two different naming systems that you can use and you might see either one used in a GAMSAT question so be ready for that. there we go cool some minor things that i don't think are all that useful but i'll throw them in anyway is our rna polymerase you'll notice started on the three prime end it always reads three to five and then it'll write new information five to three because dna and mrna should always be anti-parallel like that so the enzyme always red enzyme always reads three prime to five prime but it writes down complementary dna in the new stuff from 5' to 3' just like that. That's a good tip to call on in case you get anything in terms of orienting where you're at. So this is our transcription process. We've now used the DNA as the template to write out mRNA. The reason why we do this is because our protein manufacturing system cannot read DNA, it can only read mRNA. So effectively it's like it's in the wrong language and we need to translate it a bit. annoying because it's translation is the next step which is different but we're trying to transcribe and transcription rewrite it in a new language mRNA language and that will be this red compound that will then jump off and the DNA will snap back together so the DNA is not damaged in the process it's just used in the process so then we get to transcription and this one is a little bit more dynamic there's a little bit more going on so what I've got drawn here is this is my artist's rendition of a ribosome and we mentioned in the second crash course series about the fact that ribosomes key function is to manufacture protein and now we're going to actually look at how it does that so if this is our mRNA here in red right let's just say that it's the exact same as what we just had up here so it's going to be a u g c g u a a u c and what it's going to do is it's going to read it in triplets at a time so it's going to read this one this one and this one we'll just kind of chop it up and in fact that one should be kind of kicked out to the the outside let's just move that one a little bit like this okay cool and so we have three different regions of the thing now the ribosome i'm not really too fussed about again the details of that they're not really going to pick on your knowledge of the structure of a ribosome all we want to understand is why is it that mRNA is turning into protein? How does that actually happen? So it does it via tRNA, which is another RNA molecule, which carries with it a specific amino acid. Remember that proteins are just a chain of amino acids stuck together and then folded up into a shape so i always remember aug here because my birthday is in august so i remember my life started in august and therefore every single protein starts with aug weirdly the code on the mrna is always aug so complementary to that let's do another color here would be a so it would be uac that would be part of the trna molecule they kind of have this weird kind of t or cross shape and then it's carrying on it a particular amino acid which we're just going to use little shapes for the moment. And the idea is that the tRNA is brought in because it's complementary to the mRNA. And then it'll read the next triplet. And that will be corresponding to a complementary code of, let's see, C would go to G, C, and then A. And the tRNA that has that in its sequence will carry a different amino acid, right? So it might carry, I'll do a triangle. And what will happen is there'll be a joining between those amino acids and the tRNA will get kicked out. all that really matters is we're using the mRNA to attract in or bring in the correct tRNA carrying a specific amino acid which allows us to control the sequence of amino acids in the protein as this chain keeps growing and the ribosome runs along the mRNA strand then this polypeptide many peptide links Between the amino acids will get larger and larger and then it'll fold into a protein and that is the translation process And there we go That's it. So the whole thing of gene expression is just being able to switch on a gene and then transcribe it into mRNA and then translate that mRNA into a polypeptide which turns into a functional protein. There we go. Any errors in that process can lead to a non-functional or dysfunctional protein as well and that can have some kind of consequences but we don't need to be able to predict the specific consequences. So then the next thing is enzymes. So enzymes come up a lot in the different questions. You'll probably be thrown some random enzymes that you're not familiar with. That's totally fine. A good trick, though, is enzymes often end in A-S-E. If ever you see A's at the end, lipase, protease, that kind of thing, then they all must be enzymes, but not all enzymes end in ASE. So you've got things like pepsin, for example, which does not end in ASE, but is an enzyme. But if it doesn't in ASE, you know it's got to be an enzyme. So they're a special type of protein, actually. So they would be manufactured in the same way that we saw before as other non-enzyme proteins. What they do is they increase the rate of reaction and they also decrease the activation energy of a reaction, i.e. they lower the amount of energy required to get that reaction to go forward. So we can think of them as like a biological catalyst, effectively. So a catalyst in chemistry just means any compound that decreases the activation energy. energy and therefore raises the rate of reaction. Enzymes are a special biological type of catalyst. They're a protein catalyst. And so I've put in here an example of what's called an energy profile diagram. And you may get thrown one of these, but it's pretty, again, pretty unlikely that you'd need to come in with prior knowledge. You can usually work with them. But just as a visual, the idea is that over here we have energy level in arbitrary units. And over here we just have reaction progress. You can measure energy in kilojoules and stuff, but we're not going to fuss about the maths on it. As the reaction goes, so we've got the first straight line is the energy of the reactants. The last straight line is the energy of the products. And the change in between is what happens as the reaction progresses. So the black solid line is if it were to be uncatalyzed, it requires an amount of activation energy, often written as EA. But then once it reaches its peak, it then drops and it loses some energy as the bonds form or break. And then you end up with a new amount of energy, right? This is an example of something called an exothermic reaction, which we've already covered in the chemistry crash course video. So I'll link that as well. But there's an overall loss of energy. And the overall change is from the starting point to the ending point. That's the enthalpy, which in this case is negative because it's a drop. What we're more interested in is what happens when you add a catalyst. So the catalyst is shown with the red line. And you can see that it's lowering the... peak energy so the activation energy doesn't have to get quite as high in the catalyzed reaction but otherwise the line goes in the same position everywhere else it meets back up with the curve and it does not change the energy level of the reactants in the product because it's not changing the outcome of the reaction it's just changing the amount of energy required and also how quickly that reaction takes place the way that it does that is it often holds onto a compound called its substrate using an act site and an active site should always be complementary to a substrate kind of like lego blocks kind of tessellating or fitting together and what it does is it holds onto the substrate and therefore increases the likelihood of its reactive surface meeting another compound and when we look at things like collision theory we say that you know the more successful collisions there are per second the higher the rate we've talked about that before as well so if you've got an enzyme that is literally orienting a compound for you then it's rigid reducing the variability of how they can interact and therefore increasing the likelihood of a successful collision with the right amount of energy and then the right orientation as well. And this is how it helps. So if we draw that out, let's say we have an enzyme like this that kind of looks like Pac-Man. So it's a bit wonky. This is going to be our enzyme. This here would be the active site, this kind of region. And so we need a substrate that is complementary to it. And so if I draw out, for example, a bunch of different compounds, this maybe would test quite well. actually fit there but even better would be something that reacts with the whole surface like this all right it doesn't have to complete a circle either it could be something you know it could be doing like this it doesn't matter the idea is it's in contact with that reactive surface of the enzyme or the active site like that so this would be our substrate right if it doesn't tessellate well it's not the right substrate for it every enzyme has a specific substrate that it works with, but often they can also bind some other similarly shaped compounds, which might then prevent its action and like inhibit or block it in some way. Then finally, we need to just understand with enzymes when they're functioning, they're very particular. They require very specific pH and temperature levels, often referred to as optimum conditions. So I've drawn two graphs in one here, and this is more of a theoretical understanding of it. We want to understand what happens. to enzyme activity under varying temperature and under varying pH. Under varying temperature, there's a window of temperature that is perfect for it, that it'll work at very, very actively. But then as you lower the temperature, the enzyme will start to become dormant, we'll say. It's almost like, you know, it's like freezing it and it going cold and stiff and not being able to move in any way. But you can thaw it back out and you can raise the temperature and its activity will come right back. If you raise the temperature, temperature beyond its limits it will actually start to denature that protein or denature that enzyme and it'll actually interfere with its structure so that it can no longer bind its substrate and it becomes non-functional. So too high a temperature and you can effectively burn or boil your your enzyme and that is denaturation. So what I do with the red line here is if this axis here is temperature and this axis here is just arbitrary activity we can see that as you raise the temperature it becomes more and more active till it reaches its peak or optimum temperature. And there's some kind of range where it's pretty high. That's its optimum range. But then once you go too high, it just very quickly dips off. And that's because the protein is denaturing. The important thing is denaturation is irreversible. Once you've denatured your protein, you can't get it back. You need to get new protein at that point. And so I use this graph because if you think about it, if you were down here on the hill, you can walk up the hill, right? You can regain that activity. If you roll off the hill, you lower the temperature. You can just walk right back. It's a slow, gradual process. If you look at the other side, it's a very steep drop-off. If you raise the temperature too high and you fall off of the side there, there is no getting back. So it's just an analogy for it. But often you see quite a steep drop-off like this with high temp too. The other one then is the pink graph, and that is with pH variation. So if we change this axis now to pH, this one has a steep drop-off on both sides. So it's not going to actually... look like a rectangle in terms of its activity graph but again it's that analogy it's got an optimum ph range right that it'll work at but then once you go too low i.e too acidic you can actually denature the protein just like that in the same way and you can't get back you can't climb back up that if you raise the ph too high and you go too alkaline or too basic you can also denature the protein so it denatures on both ends so it's a lot more sensitive to ph in that sense you And so we just want to understand this because if you got a question that was in the answer, say mentioning something about high temperature, you know that that may cause denaturation and that may then impact your reasoning for the answer. I can't really give you a specific one because every enzyme has a different optimum temperature and optimum pH range. So it depends on the one, but they would probably give you a graph or give you some information. They're not expecting you to just randomly know which ones they are. Although if there was anything that was potentially helpful. any of the enzymes that operate in the body probably have an optimum temperature somewhere around body temperature of, you know, 36, 37 degrees. If you lower the temperature or raise it beyond, say to 40 degrees or 50 degrees, then you're probably going to be denaturing that protein at that point. That's a good way to look at it. If it's a protein that's in the blood, even though you don't need to know the pH of the blood, it is good to know that the pH of blood is around about 7.4. And so again, if you have to guess at what the optimum pH is for an enzyme, operating in the blood then it would probably be around the 7.4 mark right it might prefer 7.2 but you know 7.4 it hasn't fully denatured at that point we see some variation in it all right the next one then is very much a skill rather than theory but it does come under the the label of biology so hormone maps so when we're looking at hormonal maps we talked about the endocrine system in the last video on all different body systems you can have stimulation and inhibition as the two key outcomes. They're often represented as pluses and minuses in little circles, but sometimes stimulation is also shown as an arrowhead and inhibition is shown as a blunt or flat end like this as well. Usually you'll see this from GAMSAT from what I've seen, but you may see this as well. So we're going to be ready for both. What we want to be able to do is really quickly analyze hormonal maps so that we're not relying on the context of the question, because otherwise that becomes too question specific. you want to be able to look at these as a Problem solver so that you can adapt it to any kind of hormonal map question. And then we'll also look at neural maps, which work in pretty much the exact same way. So I like to think of even though a hormone is not really an on-off switch, you can analyze these maps like on off switches otherwise you can use increase decrease notation as well or more or less is something that i often use so if we look at this one you don't really need to come into it with any knowledge of what any of this actually means. You might recognize this is from a previous sample section three video that I did. It's just a really good demonstration of the ways in which enzymes can operate. So if we look at, for example, renin over here, we'll just pick a random one, right? It's got a stimulatory response on this process, this conversion. So all we need to really be able to do is know what happens when you increase one of these enzymes. So if I increase the amount of renin, then I get more of this. And I like that. like to think of stimulation as working directly and inhibition working oppositely meaning that if you've got a stimulatory path more of it means more stimulation less of it means less right if you've got an inhibitory path more inhibition means less of its output and less inhibition means more of its output so it goes in reverse right that's a really simple way of breaking down these kind of uh these kind of maps so if i have more renin because it's stimulatory then i know that but I can just follow the path of, it's like an on switch, right? So it's on, so more, I like to do arrows, more of this, then this goes, more of this, it's just more arrows, which then means more of this, more of this, more of this, more of this, more of this. And I can just keep tracking the impact as I go around the loop like that, right? And so therefore I can make a statement that more renin means, say more aldosterone secretion. Done, there we go. And the idea is the question will hint at where you're starting. and where you need to end and you just follow the map through that path if we look at an inhibitory pathway instead let's say we look at i'll do it in red as well why not let's look at say the inhibition of the kidneys here that is coming from water and salt retention right so this is going to be a particular stimulus and so if we got say more water and salt retention we've now got an off switch so we get this gets shut down right so therefore we get less renin and because this is all positive it keeps going less and less like that. Now, obviously, that's a quite simple one there. So let's just create a slightly more complex one without any context for the biology. So say that we just have all these little blocks and I don't really know where this is going. I'll just make it up. see what happens so let's just call them enzyme a b c d e and f and then i might as well color code as well so it's a little bit easier to track we're going to go stimulation stimulation stimulation and maybe stimulation here but then i'm also going to put in some inhibitory paths as well So inhibition, inhibition, inhibition, and inhibition, like that. And now I'm going to see what happens. Let's say that we do an increase in A. What's that going to do to, say, F? And so all we have to do here, I'm going blue. So if we increase this, I'm trying to get over here. So I follow the arrows around and I go, all right, positive. So that has the same impact, right? Then from there, because this is inhibitory, you're going to get. get the opposite effect right so if i've got more of b then i get more uh inhibition of d which means i get less d and then because that's got an inhibitory effect it's going to flip back around again i get more so therefore an increase in a means an increase in f done shows that you don't have to have any actual biological knowledge at all to read a hormonal pathway you just have to think about them as on off switches or ups and downs positives continue doing the up arrow or the down arrow whichever you start started with whenever it flips to negative it means flip the arrow around it's a nice really fast way to break down hormonal and neural maps and so we can do the exact same thing if we have a neural map here right um we can do the same thing we don't have to know what any of this actually means and truthfully i did a neuroscience major and i can't remember um some of these i can recognize a few of those names but all the details of neuroscience just dropped very very quickly for me i never used it again So, if we were to look at, say, this one on the left, right, we can do the same thing. We've got, so red is going to be stimulatory. And it's a little bit counterintuitive, but I've just grabbed this off the internet, so who knows where it came from. Blue is going to be inhibitory each time, right? So a little bit counterintuitive on the colors, but we'll go with it. So let's say we have an increase. in glutamate to start with and we'll just trace it around and let's see what's going to be the impact on the GPE which can I remember what that actually stands for I don't think so GPE no can't remember remember at all. So if I have more of this, then I'm going to trace, I'm trying to get to here. So I can see some arrows pointing down this way. And then I can also see there's another path that goes out this way and I can loop in here. So I'm going to look at both of those and see about their impacts. So if I have more glutamate, then it means I have more excitation of the striatum. If I go down the D2 receptor this way, then it means I have less stimulation of GPE because I have more inhibitor. of it right so all of my arrows are to do with stimulation so lower means inhibition if i have less inhibition from there then that was a decrease if i follow a different path i can also go this way we said right and so if i do that i've got cortex being stimulated that has an excitatory impact on the stn and therefore that then has looks like an excitatory i would say as well because there's no blue and it's got an arrowhead that would be an increase so because i've got a decrease and an increase that is in some ways kind of ambiguous i've picked this out at random so you may not get one quite as complicated as this but then another thing to consider is you've also got this little indirect gabber pathway going here as well so from the first one there was a decrease in gpe which means then an increase in stn and therefore an increase in gpe The other one was an excitation here. So an excitation of GPE, which would mean more inhibition, which would mean a decrease. So again, it's a bit ambiguous from that one. So this could happen in an answer. It would just mean that it wouldn't give you a conclusive answer, which would mean that it probably isn't the right one in that case. And then finally, it's just metabolism and photosynthesis. So this is, again, a point of theory, but we just want to draw out some of the key takeaways from each of these processes so that we can apply them in the bio questions. So with metabolism, it's actually... a breakdown of two different processes. We've got catabolism which is the breakdown of compounds and the freeing of electrons from bonds whereas we've also got anabolism which is the build-up. the gluing together of things put those two together and you get metabolism like that so the build-up and breakdown so it's both the storage or the formation of sugars for energy storage or carbohydrates i should say and then it's also about the breakdown of them and their use in the muscles and the tissues so if we look at basic metabolism what we're doing is we're taking glucose and we're putting it through a process called glycolysis this is happening in the cells, and then this breaks it down. We'll do a couple of little details, but again, I wouldn't necessarily go in memorizing all of this to lots of a compound called pyruvate. When we get pyruvate in that process, we actually produce, or we net produce, to ATP. And you've probably seen these in the questions before. ATP is a compound that actually stores electrons for us and therefore is referred to as an energy carrier. And we use these as a way of protecting the electrons so that we can train them. transfer them between compounds for use. And so our whole goal is to build up ATP stores, right? So this is when we're actually spending that glucose and getting that ATP out so that we can send it off to the tissues to be used. Or it might already be out the tissues. The pyruvate, though, can keep getting processed further, right? So it gets processed into acetyl coenzyme A. And again, don't bother memorizing any of this. And then it sends into another cycle called the Krebs cycle. and this actually occurs in the mitochondria and i forgot in my cell structure video to mention mitochondria is one of the key um one of the key organelles and the fact that it is the powerhouse of the cell which we've heard before so krebs cycle actually keeps making more atp right and other energy carriers which we don't really care about their details you And then from that, we spend a little bit, we sacrifice a little bit of that energy. We then go further, still in the mitochondria. And then we have another thing called the electron transport chain or ETC. And from that, we get quite a bit more. We get 32 to 34 ATP. All the numbers are totally useless. You don't need to know them. But it's just to give you a sense of where most of our energy is. energy comes from right we get very little out of glycolysis we get a lot more out of the electron transport chain and all of this happens in the mitochondria right so the mitochondria is where we get the bulk of our energy production once we get to the end though we've spent the energy and that's it then we have to go finding more glucose or finding more stores of glucose and that's why we have a diet right if we look at plants i always say energetically plants are much much better than humans and all other animals because they actually generate and recycle their energy to produce their own food. So they're not dependent on a diet. They can actually generate it from the energy that they make. So what plants will do is they also squeeze out an extra step. They get photosynthesis. And what they're doing in photosynthesis, which I'm sure you're already familiar with the basic concepts, that is storing energy from UV light in its own photosystems for then use, right? And it produces energy carriers. And so it does that in the chloroplasts. But remember that plant cells also have mitochondria and everything else, so they can do everything that we can do. They just add on an extra step. And in that process, they get another effective run of the electron transport chain. So they really pump ATP out of their sugars. And in doing that, so they have UV light goes in. And then out of that, they get another 32 to 34 ATP out of that system. And then on top of it. that what they're also doing after that is they're spending a little bit of it and not all of it but then they're converting co2 into glucose so they can actually make their own food at the same time and then that food goes right back into their metabolic cycle which is just like ours so they can actually take that glucose and send it right back and then start processing it to generate more energy from it again so they have the full deal of it right some of the key factors that go into photosynthesis though it's probably worth knowing the chemical equation just in case so it's all six co2 if we want to balance it we may as well plus six waters goes into six carbon not carbon dioxide six oxygens plus one glucose and the idea is that when we respire or spend our energy we're actually going this way we're reversing it we're using glucose and breathing in oxygen to spit out CO2 and we also make water in the process. Plants do that, but then they also need water so that they can fix carbon dioxide and fix it into a fuel for themselves, just like that. That's the basics of it. And a nice little kind of wrap up is if I just do a nice little drawing of a tree here, like this, here's our photosynthesizing tree. Here's our human. This is how we interact with it. It's spitting out oxygen. We're breathing that oxygen in. We're then spitting out CO2 and it's fixing the CO2 like that, right? As well as that, we kind of eat the plant. We probably don't eat trees, but now say it's a stem of broccoli. We get glucose out of it, right? And we get other sugars and fuels. And then from that, we spit out water. Let's just say it comes out in urine, for example. And then we use that water. It's not quite how it is, but there's a nice interaction there. We use that water, we water the plants and they can store that water. use it to then reproduce at the same time cool and we get this nice little interaction between them it's possible that you may get a question relating to some kind of interaction but it's very very minor figured i'd just throw that one in there though to give it some context And there we go. That's the basics of everything, right? So yes, metabolism is a much, much bigger topic, but I don't think that it's all that relevant to know every little step. It probably speeds up your familiarity with processing the question for sure. But from the questions... I've seen about metabolism they're actually not bio-related they're more chemistry related and in that case you're just looking at patterns so you don't really need to be familiar with the compounds it definitely helps if you want to go and look at that then be my guest but I don't think that there's all that much much value for the or much reward for the effort that goes into it so realistically you could probably go into a chemistry metabolism question just looking at it as a pattern recognition thing rather than having to know a lot of the deep background behind it but there we go so that then wraps everything up you can see that biology is much more skills based there's only a few points of theory along the way that you need to to know and so hopefully this crash course series has wrapped that up for you and helped kind of define the limits of what you need for GAMSAT. As always though this really is the bare bones of the principles that you need. I'm definitely not saying that if you watch these videos that you'll suddenly be guaranteed a boost in your section 3 score. It is ultimately about problem solving but now you've actually got the skills that you can use to start grappling with those questions and processing the information. If you're going blind it's very very confusing and you'll notice that you don't actually use a lot of the theory all that much. much. It's just there to confirm your thinking or to speed up your answering. The only place that I would say that you really use theory a lot more is in the chemistry questions. It lends itself to it, but it's still not the majority of the questions. For the most part, it's problem solving. Anyway, hopefully you've enjoyed this one as well. Leave me some feedback on the series. I've had a bit of a request to do a math crash course series, so I'll probably look into doing that. It'll probably be early next year though, because I'm planning to go on a break pretty soon at the end of this week, but I will work on that. one as well that should be a pretty interesting one i've also got to set up a playlist for the other two maths videos that i've done if you haven't checked those out check those out as well otherwise that's really it there if you haven't already seen the physics and the chemistry crash courses i will put them up on the screen here and here and you can go and watch those as well get right up to speed all the best with all of the practice questions anyway i will see you guys in the next one

Today what we're going to do is actually go through the very last of the biology crash course. series which has happened very very quickly this will be the fourth installment over the course of just four weeks basically and I've already done these for chemistry and physics as well and we kind of kept them down to about three and a half to four hours or so to really prove that you can condense the theory that you actually require for the test into a relatively short amount of content. Of course this is stripped back, it is just the bare essentials and realistically the highest yield stuff. There may be little bits and pieces that you might find in a question but has it been repeated?

No. So we're really looking at people with a non-science background can kind of go through these videos, brush up on all the skills so that they know what they're actually supposed to be studying. studying for because the world of chemistry physics and biology is very very broad and there's really not that many things that GAMSAT's really requiring of people we're seeing a new structure that they're definitely introducing concepts to you what we focus on in this is getting you familiar with those concepts so that you're not relying on learning information at the same time that you apply it if you would go in blindly into the GAMSAT with no prior knowledge then it would be very tricky to actually navigate the information and every now and then we do find that they do test some prior knowledge but for the most part it is a reasoning test you want to be focused though on actually applying the reasoning not any kind of learning so with the bio one we know that it's much much less content based for sure compared to something like say chemistry and so with this series it's a little bit different in that we are looking at familiarity with the words understanding how cells function understanding how systems function so that when you go into the actual information you kind of have those basic assumptions under your belt and as well as that you're not going to be thrown or phased by any of the wording that's used. So with today's one anyway it's a bit of a mishmash of topics really.

We've gone through and themed all the previous ones but today's one is really just a bit of a mishmash of topics that are kind of left over that didn't really fit in anywhere perfectly. I figured that would happen, bio is a pretty big topic and so we're going to go through a bit of a mix of things. We're going to start with gene expression which kind of links into a bit of the genetics from the second one.

uh from the first one actually that was then we did cell structure second then we're going to go through enzyme activity and how enzymes function as well because they seem to come up a lot in gamsat questions we want to be familiar with those then we're going to go through how to read hormonal and neural maps as well in terms of cell signaling and excitation and inhibition or stimulation and inhibition and then finally we're going to end on some metabolism and photosynthesis because again it's a little bit more theory based but we see that some assumptions and knowledge in this can be helpful in GAMSAT as well. So I'm going to try and keep it relatively short. Hopefully we're going to aim for about 40 minutes or so to get this one knocked out and then you'll be on your way to answering questions.

All right so the first thing that we're going to do is go through gene expression and what this really is. This is a very very useful topic because although it may not always be assessed in terms of just translating say the nucleotide base sequence code backwards and forwards, it is really important to understand the basics of what gene expression is because it underpins a lot of the questions relating to genetics and you can extrapolate from here so the first thing is what is it it's really just the process of how we take dna into a final protein product right and there's two key steps i'm going to leave out there is a third step but i'm going to leave that one out because i don't see it as relevant to gamsat i'll mention it when we come up to it so that you can research it if you want to but i don't think it's all that useful the first one is here we convert DNA into mRNA and this process that takes us through this is transcription. And so we'll look at that first that's going to be step one. Now along the way here we technically do modify the mRNA and that's the step that I'm going to leave out because if it gets thrown in they will introduce any key facts that you need for the question and you'd probably be fine to work with the information. given.

I don't think it's worth knowing it. It's a bit too technical and a bit too theoretical. The second step then takes us from mRNA into polypeptide, or really just a sequence of amino acids that can fold into a protein.

So this is going to be translation. and that will be our step two that we'll go through. So starting off with transcription, I'm just going to zoom in here.

We start with our DNA compound. Yeah, this will be our DNA. Now really DNA is a very very long long molecule, but along the way sections of it will be genes and we've talked about this in the first of the BioCrash course series.

And so we've now isolated one of these genes, we're just looking at part of it, and it's obviously very very short. Most genes are going to be in the hundreds to even thousands of nucleotides long, we're only drawing 10ish or so, so obviously a much simplified version of it. And so I'll point out we've mentioned these before, we have 3 and 5 prime end, these are just ways to identify which end of the compound we're talking about.

It relates a little bit to the structure, the 5 prime end has a free phosphate and the 3 prime end has a free sugar. On its end, it's pretty unlikely for that to be all that relevant to a GAMSAT question though. But I put these in so that we can kind of distinguish where we are.

And so on one end, we're going to have this red circle here, which is going to be an enzyme called RNA polymerase. Now, again, you don't have to memorize names or anything like that. I'm just going to reference them so that you're familiar with the words, so that if they do talk about that, you already have heard the word before. You don't need to go memorizing what RNA polymerase is. how it functions and all the rest of it, they will guide you through that in the stem.

We just want to understand what the process here is. So this enzyme will actually attach to one of the two strands, in this case this bottom one, and what it's going to do is it's going to run along the DNA and read it and then lay down complementary RNA nucleotides, which we talked about. So remember that the code is A to T, G to C and vice versa.

But because we're dealing with mRNA, we don't actually have thiamine in there. We have uracil instead, uracil. And so this will be the U. And so if I make up, for example, a nice simple one, let's do T-A-C, and then we'll just make up stuff like G-C-A-T-T-A-C, or G. There we go.

So complementary to that, we'll do that on the other side, and I might just color code this, would have been... A, T, G, C, and then to C would it be G, T, A, A, T, C, like that, right? So that's all pretty familiar. And so as the RNA polymerase runs along, what it's going to do is lay down complementary mRNA.

So what I might do here, just to make life a little bit easier for myself, is if I can grab it all, just about. I'm just going to bring that up a little bit to create a bit of space. And...

Here we go. Cool. Alright, and so as it runs along, let's say it's already kind of started its way along, and opposite to T, it would have laid down an A. Opposite to A, it would have laid down a U, and then opposite to C, it would have laid down a G, like this. So you get A, U, G, and it's going to keep going, right?

So if it continues to slide along, then next up it would see G, and so it'll put down a C, and so on like this, right? there then AAU and oh see just like that and this here is going to be our mRNA molecule like that. Now you might notice a pattern right of course it's complementary to the bottom strand but it's also effectively identical to the top strand that got kicked out of the way right in the process so So the reason why as well, I forgot to mention, it bubbles out like this just so that it can access the DNA. But that bubble will run along and reclose behind it.

So I've not really drawn it correctly because... Further down here, by the time it reaches this point, the bubble will have opened there to access the DNA. But I can't really animate it too well with a diagram.

But I would recommend I'll link below as well some YouTube videos that do a really good job of showing that animation much better than I can do here. So you can watch those as well. The other thing that you can watch is if you go to like my super, super old videos, although that was only like four months ago. I started this channel really just making videos for my high school students.

And so for my buyers. students i put together a three-part series going through transcription modification and translation if you want to watch those i'll link those below as well actually that'll probably be easier you can watch those they're in a lot more detail so you definitely wouldn't need to know them in quite the same detail because that's for my vce students but um in it i have a pretty good animation of where i i drew rna polymerase on my finger and used an analogy of a um a resealable sandwich bag for this particular thing that might be helpful so watch that one as well you but once it gets to the end everything kind of drops off and so we end up with this strand here and so the mRNA you can see is actually completely identical to this purple strand all the way along the only difference is that where we have T's we should have U's and in fact I made a slight error there that should be a U because because this is mRNA whereas this is just DNA like that and so this thing creates a little bit of naming structure which you want to be familiar with because they will probably use it if they go into this topic and that is that the bottom strand here because it's being read by the RNA polymerase then it's acting as a template so it's often called the template strand and so therefore the other strand of DNA would then be the non template strand like that. Annoyingly though there's a second naming system and it flips what is non.

So as well as that you'll notice that the top strand the non-template strand is also identical to the mRNA i.e. it codes for the mRNA. So this is often referred to as the code strand and because the bottom strand is opposite to it it's often referred to as the non-coding strand. So there are two different naming systems that you can use and you might see either one used in a GAMSAT question so be ready for that.

there we go cool some minor things that i don't think are all that useful but i'll throw them in anyway is our rna polymerase you'll notice started on the three prime end it always reads three to five and then it'll write new information five to three because dna and mrna should always be anti-parallel like that so the enzyme always red enzyme always reads three prime to five prime but it writes down complementary dna in the new stuff from 5' to 3' just like that. That's a good tip to call on in case you get anything in terms of orienting where you're at. So this is our transcription process.

We've now used the DNA as the template to write out mRNA. The reason why we do this is because our protein manufacturing system cannot read DNA, it can only read mRNA. So effectively it's like it's in the wrong language and we need to translate it a bit.

annoying because it's translation is the next step which is different but we're trying to transcribe and transcription rewrite it in a new language mRNA language and that will be this red compound that will then jump off and the DNA will snap back together so the DNA is not damaged in the process it's just used in the process so then we get to transcription and this one is a little bit more dynamic there's a little bit more going on so what I've got drawn here is this is my artist's rendition of a ribosome and we mentioned in the second crash course series about the fact that ribosomes key function is to manufacture protein and now we're going to actually look at how it does that so if this is our mRNA here in red right let's just say that it's the exact same as what we just had up here so it's going to be a u g c g u a a u c and what it's going to do is it's going to read it in triplets at a time so it's going to read this one this one and this one we'll just kind of chop it up and in fact that one should be kind of kicked out to the the outside let's just move that one a little bit like this okay cool and so we have three different regions of the thing now the ribosome i'm not really too fussed about again the details of that they're not really going to pick on your knowledge of the structure of a ribosome all we want to understand is why is it that mRNA is turning into protein? How does that actually happen? So it does it via tRNA, which is another RNA molecule, which carries with it a specific amino acid.

Remember that proteins are just a chain of amino acids stuck together and then folded up into a shape so i always remember aug here because my birthday is in august so i remember my life started in august and therefore every single protein starts with aug weirdly the code on the mrna is always aug so complementary to that let's do another color here would be a so it would be uac that would be part of the trna molecule they kind of have this weird kind of t or cross shape and then it's carrying on it a particular amino acid which we're just going to use little shapes for the moment. And the idea is that the tRNA is brought in because it's complementary to the mRNA. And then it'll read the next triplet.

And that will be corresponding to a complementary code of, let's see, C would go to G, C, and then A. And the tRNA that has that in its sequence will carry a different amino acid, right? So it might carry, I'll do a triangle.

And what will happen is there'll be a joining between those amino acids and the tRNA will get kicked out. all that really matters is we're using the mRNA to attract in or bring in the correct tRNA carrying a specific amino acid which allows us to control the sequence of amino acids in the protein as this chain keeps growing and the ribosome runs along the mRNA strand then this polypeptide many peptide links Between the amino acids will get larger and larger and then it'll fold into a protein and that is the translation process And there we go That's it. So the whole thing of gene expression is just being able to switch on a gene and then transcribe it into mRNA and then translate that mRNA into a polypeptide which turns into a functional protein. There we go.

Any errors in that process can lead to a non-functional or dysfunctional protein as well and that can have some kind of consequences but we don't need to be able to predict the specific consequences. So then the next thing is enzymes. So enzymes come up a lot in the different questions. You'll probably be thrown some random enzymes that you're not familiar with.

That's totally fine. A good trick, though, is enzymes often end in A-S-E. If ever you see A's at the end, lipase, protease, that kind of thing, then they all must be enzymes, but not all enzymes end in ASE.

So you've got things like pepsin, for example, which does not end in ASE, but is an enzyme. But if it doesn't in ASE, you know it's got to be an enzyme. So they're a special type of protein, actually.

So they would be manufactured in the same way that we saw before as other non-enzyme proteins. What they do is they increase the rate of reaction and they also decrease the activation energy of a reaction, i.e. they lower the amount of energy required to get that reaction to go forward. So we can think of them as like a biological catalyst, effectively.

So a catalyst in chemistry just means any compound that decreases the activation energy. energy and therefore raises the rate of reaction. Enzymes are a special biological type of catalyst.

They're a protein catalyst. And so I've put in here an example of what's called an energy profile diagram. And you may get thrown one of these, but it's pretty, again, pretty unlikely that you'd need to come in with prior knowledge. You can usually work with them.

But just as a visual, the idea is that over here we have energy level in arbitrary units. And over here we just have reaction progress. You can measure energy in kilojoules and stuff, but we're not going to fuss about the maths on it. As the reaction goes, so we've got the first straight line is the energy of the reactants.

The last straight line is the energy of the products. And the change in between is what happens as the reaction progresses. So the black solid line is if it were to be uncatalyzed, it requires an amount of activation energy, often written as EA. But then once it reaches its peak, it then drops and it loses some energy as the bonds form or break.

And then you end up with a new amount of energy, right? This is an example of something called an exothermic reaction, which we've already covered in the chemistry crash course video. So I'll link that as well. But there's an overall loss of energy. And the overall change is from the starting point to the ending point.

That's the enthalpy, which in this case is negative because it's a drop. What we're more interested in is what happens when you add a catalyst. So the catalyst is shown with the red line.

And you can see that it's lowering the... peak energy so the activation energy doesn't have to get quite as high in the catalyzed reaction but otherwise the line goes in the same position everywhere else it meets back up with the curve and it does not change the energy level of the reactants in the product because it's not changing the outcome of the reaction it's just changing the amount of energy required and also how quickly that reaction takes place the way that it does that is it often holds onto a compound called its substrate using an act site and an active site should always be complementary to a substrate kind of like lego blocks kind of tessellating or fitting together and what it does is it holds onto the substrate and therefore increases the likelihood of its reactive surface meeting another compound and when we look at things like collision theory we say that you know the more successful collisions there are per second the higher the rate we've talked about that before as well so if you've got an enzyme that is literally orienting a compound for you then it's rigid reducing the variability of how they can interact and therefore increasing the likelihood of a successful collision with the right amount of energy and then the right orientation as well. And this is how it helps.

So if we draw that out, let's say we have an enzyme like this that kind of looks like Pac-Man. So it's a bit wonky. This is going to be our enzyme.

This here would be the active site, this kind of region. And so we need a substrate that is complementary to it. And so if I draw out, for example, a bunch of different compounds, this maybe would test quite well. actually fit there but even better would be something that reacts with the whole surface like this all right it doesn't have to complete a circle either it could be something you know it could be doing like this it doesn't matter the idea is it's in contact with that reactive surface of the enzyme or the active site like that so this would be our substrate right if it doesn't tessellate well it's not the right substrate for it every enzyme has a specific substrate that it works with, but often they can also bind some other similarly shaped compounds, which might then prevent its action and like inhibit or block it in some way.

Then finally, we need to just understand with enzymes when they're functioning, they're very particular. They require very specific pH and temperature levels, often referred to as optimum conditions. So I've drawn two graphs in one here, and this is more of a theoretical understanding of it.

We want to understand what happens. to enzyme activity under varying temperature and under varying pH. Under varying temperature, there's a window of temperature that is perfect for it, that it'll work at very, very actively. But then as you lower the temperature, the enzyme will start to become dormant, we'll say. It's almost like, you know, it's like freezing it and it going cold and stiff and not being able to move in any way. But you can thaw it back out and you can raise the temperature and its activity will come right back.

If you raise the temperature, temperature beyond its limits it will actually start to denature that protein or denature that enzyme and it'll actually interfere with its structure so that it can no longer bind its substrate and it becomes non-functional. So too high a temperature and you can effectively burn or boil your your enzyme and that is denaturation. So what I do with the red line here is if this axis here is temperature and this axis here is just arbitrary activity we can see that as you raise the temperature it becomes more and more active till it reaches its peak or optimum temperature.

And there's some kind of range where it's pretty high. That's its optimum range. But then once you go too high, it just very quickly dips off. And that's because the protein is denaturing.

The important thing is denaturation is irreversible. Once you've denatured your protein, you can't get it back. You need to get new protein at that point. And so I use this graph because if you think about it, if you were down here on the hill, you can walk up the hill, right? You can regain that activity.

If you roll off the hill, you lower the temperature. You can just walk right back. It's a slow, gradual process.

If you look at the other side, it's a very steep drop-off. If you raise the temperature too high and you fall off of the side there, there is no getting back. So it's just an analogy for it. But often you see quite a steep drop-off like this with high temp too. The other one then is the pink graph, and that is with pH variation.

So if we change this axis now to pH, this one has a steep drop-off on both sides. So it's not going to actually... look like a rectangle in terms of its activity graph but again it's that analogy it's got an optimum ph range right that it'll work at but then once you go too low i.e too acidic you can actually denature the protein just like that in the same way and you can't get back you can't climb back up that if you raise the ph too high and you go too alkaline or too basic you can also denature the protein so it denatures on both ends so it's a lot more sensitive to ph in that sense you And so we just want to understand this because if you got a question that was in the answer, say mentioning something about high temperature, you know that that may cause denaturation and that may then impact your reasoning for the answer. I can't really give you a specific one because every enzyme has a different optimum temperature and optimum pH range.

So it depends on the one, but they would probably give you a graph or give you some information. They're not expecting you to just randomly know which ones they are. Although if there was anything that was potentially helpful. any of the enzymes that operate in the body probably have an optimum temperature somewhere around body temperature of, you know, 36, 37 degrees. If you lower the temperature or raise it beyond, say to 40 degrees or 50 degrees, then you're probably going to be denaturing that protein at that point.

That's a good way to look at it. If it's a protein that's in the blood, even though you don't need to know the pH of the blood, it is good to know that the pH of blood is around about 7.4. And so again, if you have to guess at what the optimum pH is for an enzyme, operating in the blood then it would probably be around the 7.4 mark right it might prefer 7.2 but you know 7.4 it hasn't fully denatured at that point we see some variation in it all right the next one then is very much a skill rather than theory but it does come under the the label of biology so hormone maps so when we're looking at hormonal maps we talked about the endocrine system in the last video on all different body systems you can have stimulation and inhibition as the two key outcomes. They're often represented as pluses and minuses in little circles, but sometimes stimulation is also shown as an arrowhead and inhibition is shown as a blunt or flat end like this as well.

Usually you'll see this from GAMSAT from what I've seen, but you may see this as well. So we're going to be ready for both. What we want to be able to do is really quickly analyze hormonal maps so that we're not relying on the context of the question, because otherwise that becomes too question specific.

you want to be able to look at these as a Problem solver so that you can adapt it to any kind of hormonal map question. And then we'll also look at neural maps, which work in pretty much the exact same way. So I like to think of even though a hormone is not really an on-off switch, you can analyze these maps like on off switches otherwise you can use increase decrease notation as well or more or less is something that i often use so if we look at this one you don't really need to come into it with any knowledge of what any of this actually means. You might recognize this is from a previous sample section three video that I did. It's just a really good demonstration of the ways in which enzymes can operate.

So if we look at, for example, renin over here, we'll just pick a random one, right? It's got a stimulatory response on this process, this conversion. So all we need to really be able to do is know what happens when you increase one of these enzymes.

So if I increase the amount of renin, then I get more of this. And I like that. like to think of stimulation as working directly and inhibition working oppositely meaning that if you've got a stimulatory path more of it means more stimulation less of it means less right if you've got an inhibitory path more inhibition means less of its output and less inhibition means more of its output so it goes in reverse right that's a really simple way of breaking down these kind of uh these kind of maps so if i have more renin because it's stimulatory then i know that but I can just follow the path of, it's like an on switch, right? So it's on, so more, I like to do arrows, more of this, then this goes, more of this, it's just more arrows, which then means more of this, more of this, more of this, more of this, more of this. And I can just keep tracking the impact as I go around the loop like that, right?

And so therefore I can make a statement that more renin means, say more aldosterone secretion. Done, there we go. And the idea is the question will hint at where you're starting. and where you need to end and you just follow the map through that path if we look at an inhibitory pathway instead let's say we look at i'll do it in red as well why not let's look at say the inhibition of the kidneys here that is coming from water and salt retention right so this is going to be a particular stimulus and so if we got say more water and salt retention we've now got an off switch so we get this gets shut down right so therefore we get less renin and because this is all positive it keeps going less and less like that.

Now, obviously, that's a quite simple one there. So let's just create a slightly more complex one without any context for the biology. So say that we just have all these little blocks and I don't really know where this is going. I'll just make it up.

see what happens so let's just call them enzyme a b c d e and f and then i might as well color code as well so it's a little bit easier to track we're going to go stimulation stimulation stimulation and maybe stimulation here but then i'm also going to put in some inhibitory paths as well So inhibition, inhibition, inhibition, and inhibition, like that. And now I'm going to see what happens. Let's say that we do an increase in A. What's that going to do to, say, F?

And so all we have to do here, I'm going blue. So if we increase this, I'm trying to get over here. So I follow the arrows around and I go, all right, positive.

So that has the same impact, right? Then from there, because this is inhibitory, you're going to get. get the opposite effect right so if i've got more of b then i get more uh inhibition of d which means i get less d and then because that's got an inhibitory effect it's going to flip back around again i get more so therefore an increase in a means an increase in f done shows that you don't have to have any actual biological knowledge at all to read a hormonal pathway you just have to think about them as on off switches or ups and downs positives continue doing the up arrow or the down arrow whichever you start started with whenever it flips to negative it means flip the arrow around it's a nice really fast way to break down hormonal and neural maps and so we can do the exact same thing if we have a neural map here right um we can do the same thing we don't have to know what any of this actually means and truthfully i did a neuroscience major and i can't remember um some of these i can recognize a few of those names but all the details of neuroscience just dropped very very quickly for me i never used it again So, if we were to look at, say, this one on the left, right, we can do the same thing. We've got, so red is going to be stimulatory.

And it's a little bit counterintuitive, but I've just grabbed this off the internet, so who knows where it came from. Blue is going to be inhibitory each time, right? So a little bit counterintuitive on the colors, but we'll go with it. So let's say we have an increase. in glutamate to start with and we'll just trace it around and let's see what's going to be the impact on the GPE which can I remember what that actually stands for I don't think so GPE no can't remember remember at all.

So if I have more of this, then I'm going to trace, I'm trying to get to here. So I can see some arrows pointing down this way. And then I can also see there's another path that goes out this way and I can loop in here. So I'm going to look at both of those and see about their impacts. So if I have more glutamate, then it means I have more excitation of the striatum.

If I go down the D2 receptor this way, then it means I have less stimulation of GPE because I have more inhibitor. of it right so all of my arrows are to do with stimulation so lower means inhibition if i have less inhibition from there then that was a decrease if i follow a different path i can also go this way we said right and so if i do that i've got cortex being stimulated that has an excitatory impact on the stn and therefore that then has looks like an excitatory i would say as well because there's no blue and it's got an arrowhead that would be an increase so because i've got a decrease and an increase that is in some ways kind of ambiguous i've picked this out at random so you may not get one quite as complicated as this but then another thing to consider is you've also got this little indirect gabber pathway going here as well so from the first one there was a decrease in gpe which means then an increase in stn and therefore an increase in gpe The other one was an excitation here. So an excitation of GPE, which would mean more inhibition, which would mean a decrease.

So again, it's a bit ambiguous from that one. So this could happen in an answer. It would just mean that it wouldn't give you a conclusive answer, which would mean that it probably isn't the right one in that case.

And then finally, it's just metabolism and photosynthesis. So this is, again, a point of theory, but we just want to draw out some of the key takeaways from each of these processes so that we can apply them in the bio questions. So with metabolism, it's actually... a breakdown of two different processes. We've got catabolism which is the breakdown of compounds and the freeing of electrons from bonds whereas we've also got anabolism which is the build-up.

the gluing together of things put those two together and you get metabolism like that so the build-up and breakdown so it's both the storage or the formation of sugars for energy storage or carbohydrates i should say and then it's also about the breakdown of them and their use in the muscles and the tissues so if we look at basic metabolism what we're doing is we're taking glucose and we're putting it through a process called glycolysis this is happening in the cells, and then this breaks it down. We'll do a couple of little details, but again, I wouldn't necessarily go in memorizing all of this to lots of a compound called pyruvate. When we get pyruvate in that process, we actually produce, or we net produce, to ATP. And you've probably seen these in the questions before.

ATP is a compound that actually stores electrons for us and therefore is referred to as an energy carrier. And we use these as a way of protecting the electrons so that we can train them. transfer them between compounds for use. And so our whole goal is to build up ATP stores, right?

So this is when we're actually spending that glucose and getting that ATP out so that we can send it off to the tissues to be used. Or it might already be out the tissues. The pyruvate, though, can keep getting processed further, right? So it gets processed into acetyl coenzyme A. And again, don't bother memorizing any of this.

And then it sends into another cycle called the Krebs cycle. and this actually occurs in the mitochondria and i forgot in my cell structure video to mention mitochondria is one of the key um one of the key organelles and the fact that it is the powerhouse of the cell which we've heard before so krebs cycle actually keeps making more atp right and other energy carriers which we don't really care about their details you And then from that, we spend a little bit, we sacrifice a little bit of that energy. We then go further, still in the mitochondria.

And then we have another thing called the electron transport chain or ETC. And from that, we get quite a bit more. We get 32 to 34 ATP. All the numbers are totally useless.

You don't need to know them. But it's just to give you a sense of where most of our energy is. energy comes from right we get very little out of glycolysis we get a lot more out of the electron transport chain and all of this happens in the mitochondria right so the mitochondria is where we get the bulk of our energy production once we get to the end though we've spent the energy and that's it then we have to go finding more glucose or finding more stores of glucose and that's why we have a diet right if we look at plants i always say energetically plants are much much better than humans and all other animals because they actually generate and recycle their energy to produce their own food. So they're not dependent on a diet. They can actually generate it from the energy that they make.

So what plants will do is they also squeeze out an extra step. They get photosynthesis. And what they're doing in photosynthesis, which I'm sure you're already familiar with the basic concepts, that is storing energy from UV light in its own photosystems for then use, right? And it produces energy carriers. And so it does that in the chloroplasts.

But remember that plant cells also have mitochondria and everything else, so they can do everything that we can do. They just add on an extra step. And in that process, they get another effective run of the electron transport chain. So they really pump ATP out of their sugars. And in doing that, so they have UV light goes in.

And then out of that, they get another 32 to 34 ATP out of that system. And then on top of it. that what they're also doing after that is they're spending a little bit of it and not all of it but then they're converting co2 into glucose so they can actually make their own food at the same time and then that food goes right back into their metabolic cycle which is just like ours so they can actually take that glucose and send it right back and then start processing it to generate more energy from it again so they have the full deal of it right some of the key factors that go into photosynthesis though it's probably worth knowing the chemical equation just in case so it's all six co2 if we want to balance it we may as well plus six waters goes into six carbon not carbon dioxide six oxygens plus one glucose and the idea is that when we respire or spend our energy we're actually going this way we're reversing it we're using glucose and breathing in oxygen to spit out CO2 and we also make water in the process. Plants do that, but then they also need water so that they can fix carbon dioxide and fix it into a fuel for themselves, just like that.

That's the basics of it. And a nice little kind of wrap up is if I just do a nice little drawing of a tree here, like this, here's our photosynthesizing tree. Here's our human. This is how we interact with it. It's spitting out oxygen.

We're breathing that oxygen in. We're then spitting out CO2 and it's fixing the CO2 like that, right? As well as that, we kind of eat the plant.

We probably don't eat trees, but now say it's a stem of broccoli. We get glucose out of it, right? And we get other sugars and fuels.

And then from that, we spit out water. Let's just say it comes out in urine, for example. And then we use that water. It's not quite how it is, but there's a nice interaction there. We use that water, we water the plants and they can store that water.

use it to then reproduce at the same time cool and we get this nice little interaction between them it's possible that you may get a question relating to some kind of interaction but it's very very minor figured i'd just throw that one in there though to give it some context And there we go. That's the basics of everything, right? So yes, metabolism is a much, much bigger topic, but I don't think that it's all that relevant to know every little step.

It probably speeds up your familiarity with processing the question for sure. But from the questions... I've seen about metabolism they're actually not bio-related they're more chemistry related and in that case you're just looking at patterns so you don't really need to be familiar with the compounds it definitely helps if you want to go and look at that then be my guest but I don't think that there's all that much much value for the or much reward for the effort that goes into it so realistically you could probably go into a chemistry metabolism question just looking at it as a pattern recognition thing rather than having to know a lot of the deep background behind it but there we go so that then wraps everything up you can see that biology is much more skills based there's only a few points of theory along the way that you need to to know and so hopefully this crash course series has wrapped that up for you and helped kind of define the limits of what you need for GAMSAT. As always though this really is the bare bones of the principles that you need.

I'm definitely not saying that if you watch these videos that you'll suddenly be guaranteed a boost in your section 3 score. It is ultimately about problem solving but now you've actually got the skills that you can use to start grappling with those questions and processing the information. If you're going blind it's very very confusing and you'll notice that you don't actually use a lot of the theory all that much.

much. It's just there to confirm your thinking or to speed up your answering. The only place that I would say that you really use theory a lot more is in the chemistry questions.

It lends itself to it, but it's still not the majority of the questions. For the most part, it's problem solving. Anyway, hopefully you've enjoyed this one as well. Leave me some feedback on the series. I've had a bit of a request to do a math crash course series, so I'll probably look into doing that.

It'll probably be early next year though, because I'm planning to go on a break pretty soon at the end of this week, but I will work on that. one as well that should be a pretty interesting one i've also got to set up a playlist for the other two maths videos that i've done if you haven't checked those out check those out as well otherwise that's really it there if you haven't already seen the physics and the chemistry crash courses i will put them up on the screen here and here and you can go and watch those as well get right up to speed all the best with all of the practice questions anyway i will see you guys in the next one

Transcript for:Essential Biology for GAMSAT Preparation

Transcript for:
Essential Biology for GAMSAT Preparation