I'm sorry guys, I have some terrible news for you guys. I don't really get it covering this kind of thing up, but you might not have noticed, but the hair is gone. I killed it.
I assassinated my hair. It was so sad. I mean, it's not horrible, right?
It still looks like hair. That's the only criteria we have. I mean, to be fair, at least it doesn't feel like I'm carrying another head on my head.
So that's another pro. So I think we're good. I think we're good. But anyways, the plan for today is not, unfortunately, to talk about my epically cool non-existent hair anymore. The actual point of today's video is to talk about cellular energetics because we all know that we're going to be needing a lot of energy to get through school okay so this is very applicable.
You see what I did there? I made a connection to school. Oh my god this is big brain. But basically the main things you got to know for this unit are enzymes, photosynthesis, and respiration so let us get into the good stuff.
Why don't you guys challenge me to go through all of Campo? Don't worry we're getting there okay. I promise that I will get through all of Campo in these reviews.
Like really what I do to make these is I really take this fat Oh my god. I take this back, guys. I basically go from the very beginning and I just go through the chapters and see which ones are relevant.
Well, obviously, I don't start with zero every single time. I just start off where I left off from the previous one. But basically, all this stuff is coming directly from the book.
So, it should be epic. So now, before we get into the fun stuff about how cells actually obtain the energy, we gotta talk more about energy itself and how it works, okay? So, at a very high level, there's basically, like, only a few important energies that we gotta talk about for biology, right? There's kinetic energy, right? Basically, kinetic means movement, right?
So, whenever... something moving it has energy. So there's heat energy right?
The more hot something is the more energetic it is right? And also when you like rub your hands together they become hot oh my god that hurts so much. That is also heat energy. And then the last one that is probably the most relevant one that we're going to be talking about today is chemical energy.
Now the reason why this guy is so hecking important is because that is how biological systems store energy okay? Like the way I like to think about chemical energy is that it's potential energy right? Like for example if you took a book off the ground and lifted it above your head it has more potential to fall and crush your foot. So in the same way, in the bonds of molecules themselves, they have a way of like lifting these books.
They have a way of storing energy so that it has the potential to do work later. So whenever you hear chemical energy, think chemistry. And whenever you think chemistry, you think molecules. And whenever you think molecule, you think like molecules storing energy.
So it's perfect. It makes total sense. Okay, so these are basically the three energies that are relevant to biology.
But now we actually have to talk about transferring this kind of energy. And basically the science of transferring energy is called thermodynamics. Oh my god.
thermo cause energy and dynamics cause it's changing this is crazy stuff and the two things you got to know about thermodynamics are the two laws of thermodynamics big brain okay fine the secondly four sumia the zeros and third one are irrelevant to bio so why do we even have to talk about that bio is the only science out there so essentially the first law of thermodynamics is like the easiest one so if you ever like are confused what the heck the first law of thermodynamics is just remember it's the first so it's the easiest one to remember like everybody knows conservation of energy right so literally first of all it's just conservation of energy, the most self-explanatory thing out there. No, not conversation of energy, what am I doing? Well, I mean, what we're having right now is a conversation of energy, but that is not the point. So basically, you can't make energy, you can't destroy energy, but you can transfer energy from one type to another. Second law of thermodynamics.
Now, the second law is a bit more complicated because you actually have to know what entropy is. And basically, just at a high level, what entropy is, is disorder in the universe. Now, both Yusubo and AbVio don't really test. entropy that much so you don't have to have a really solid understanding of it but you do have to know that it is the disorder of the universe so for example an ice crystal is very heckin ordered right like it's literally a perfect lattice of these beautiful dots look look at this epic lattice and you can see this is like super super ordered okay but when it turns into water right all these particles are just floating around moving around like they really don't care this has higher entropy because it's not that ordered right like compared to a crystal it is not ordered at all so basically what the second law of thermodynamics says is this entropy or the disorder of the universe is always increasing no matter what the heck you do it always will go up basically saying we're doomed basically the way i like to think about it is like even if you do something to like make something more order right like let's say we put together a robot or something like the pieces are unordered originally and then we put them into an ordered robot that could do a lot more complicated stuff but in doing that we had to exhaust a lot of energy from ourselves and we gave up a lot of energy as heat and that all contributes to increasing entropy right because heat energy is basically the definition of disorder it's literally just molecules vibrate So even though your actions might cause one thing to decrease in entropy, it causes a bunch of other things to increase in entropy, so overall, the universe is always increasing in entropy. And already, you are officially an expert in thermodynamics, so get your PhD, it'll be great.
But just kidding, okay, we've got more to talk about. Basically, the fundamental equation of thermodynamics is delta G is equal to delta H minus T delta F. Now, if you don't know what the heck that means, that's totally fine.
In biology, you do not really have to... Completely understand how this equation works, but what you do have to understand is the different variables that come into play here So Delta F is our entropy. Okay, so we already know what that is That's the disorder of the universe T is our temperature now these two guys are the interesting guy So the first thing we got to talk about is gib free energy now give free energy is important because it's literally how much work a cell can do and whenever we're talking about cellular energetics we have to know how much work a cell could use the food for right like even if food has like 69 000 million grams of fat or whatever i don't know a ton of energy i don't know how grams of fat is a unit of energy but if it had a ton of energy but we couldn't use it then it's useless so delta g is what matters to us is basically how much energy can be used to do work and then delta h is your enthalpy okay and that's basically your overall total energy is basically potential energy For all intents and purposes, you literally only have to think of it as like potential energy. And selfie! Okay, so that's good.
We got that out of the way. So let's see what else we got to talk about. So let us talk a little bit more about delta G and delta H. So delta G is your change in give-free energy, right? So let's say delta G is positive, right?
Like the amount of energy you have to do stuff is increasing, right? But to get more energy to do stuff, you have to take in energy, right? The reactions with delta G is greater than zero, aka reactions that increase your ability to do work.
are not spontaneous right because like if getting energy was spontaneous i would literally be like playing video games all day not even sleeping and i would still get energy but sadly it's not spontaneous you literally have to go to sleep and let it do its job this is so sad so essentially if delta d is greater than zero it's not spontaneous it doesn't happen automatically but if delta g is less than zero you're basically spending the energy you have to do work on doing work right so you already have the energy you don't need to take anything more in so this is spontaneous it happens by itself now if you didn't understand anything i just said literally just look at this diagram and make sure you remember that delta g is spontaneity okay it tells you whether or not something is going to happen by itself or not all right then we got delta h we know that that's our potential energy and this makes a lot more sense right because we already know what potential energy is we know like a lot of the details on how it works but basically delta h is greater than zero means you're getting potential energy right so these guys are called endergon Basically they take in potential energy, they're taking in energy from the surroundings. Celsius is less than zero, basically means it's exergonic, meaning that you're releasing energy into the environment. Take for example ice melting, right?
It takes in energy from the environment to break up the bonds in the ice cube and then it becomes water. Freezing an ice cube on the other hand is you're taking the energy out of the ice cube, so it's actually exergonic. The energy is leaving the ice cube.
All right, so now that we know the fundamentals of how energy works, now we can actually start talking about the biological stuff. Now, the reason why I talked about delta H and delta G, even though like the actual variables themselves are not that tested in either of these tests, is because you have to know that there's two types of reactions, right? There's some reactions that release energy, there's some that like take in energy. And if we're able to use the energy released by one reaction and put it into another, we can actually do useful stuff. So that brings up the point of ATP and reaction coupling.
ATP basically stands for ATP Triphosphate and basically you can literally just break that word down E for adenosine is basically just adenine right so it's basically a nitrogenous base but it's adenosine so essentially that means that it has also the sugar and then triphosphate you literally just add three phosphates it's not that hard it's latin okay I don't even know if it's latin I don't know english okay triphosphate now essentially ATP is used for all the energy in the cell because the bond connecting these two phosphates is Extremely energetic and if you break it it releases a ton of energy So clearly the breaking of this bond right here is an extra agonic reaction, right? It releases energy but what's the point of releasing energy if it just floats around and doesn't do anything? What's the point of that? So what reaction coupling does is it takes an extra agonic reaction for example the breaking of this last bond and it coupled it with An ender gonic reaction.
So for a very stupid example Let's say that we wanted to melt a cube of ice and all we had on our hands with a couple blocks of ATP what you would do if you had Chop off that last phosphate group, it would release some energy, you would couple that to the reaction that melts the ice, and then boom! You got melted ice! And all you use is the energy that was stored in that ATP. So essentially that's how ATP works to power the entire cell.
And guess what ATP is called once you get rid of that last phosphate? That's right, it's ADP! Who would have guessed? It doesn't seem diphosphate! And essentially, energetic, not so energetic, gets converted back to energetic, used again, and you keep cycling this over and over again and that's how a cell keeps going.
Alright, we are going to be doing a complete 180 degree turn. Well, actually, I mean, I have to say the same direction, so it's going to be a 360, but! Now we are going to talk about enzymes because those are extremely important for everything we're going to talk about in the rest of this video.
So let's see what an enzyme is. It's basically a molecule that speeds up a reaction, right? Everybody knows this, but how the heck does it work?
So that definition could literally be written as a biological catalyst. And a catalyst is basically something that speeds up reactions selectively and without being consumed. So on this one use of O, I'm pretty sure there's a really troll question that like made you actually understand the exact definition of a catalyst.
Basically, you got to understand that the two things you got to know are it speeds up chemical reactions, it's selective, meaning it only does a specific type of reaction, and it doesn't get consumed, okay? If it gets consumed, it's actually part of the reaction, it's not a catalyst. So this is a bare bones definition, right?
So the way it works is you basically have a reaction diagram, okay? So essentially, when you want to do a chemical reaction... there's some like amount of energy you have to overcome in order to make the reaction happen this is called the activation energy so let's say you wanted to like Take a low energy molecule like ADP for example and convert it to ATP right? You have to put energy into it. But before that reaction is gonna happen You first have to get it over the original hump and then it'll go down a little from there So the one thing you gotta know about Activating energy is that it's basically how much energy you have to put in before a reaction happens by itself and the way that Enzymes speed up this reaction is that it shortens this hump Okay So essentially your EA with the enzyme is gonna be a little bit lower the start and end points are exactly the same right because You start with the same thing you end with the same thing, but it takes less energy to get the reaction started.
So basically an enzyme looks kind of like this there's a notch right here called the active site and then the molecule that's part of the reaction that is trying to speed up goes and docks right in here and the molecule that the enzyme acts on is called a substrate. Now the enzyme can speed up a reaction in a ton of ways right like you can bend up the substrate so that it's in a better form to participate in the reaction right or for example it has to go over that activation energy right basically what the enzyme could do is that it could increase the energy of the molecule so that it's closer to the top state. Also one good thing I forgot to mention, remember that the top state is the transition state, okay?
Basically in every single reaction, what happens is that your reactants are converted to the transition state, which is high energy, and then just goes downhill from there. So active side and substrate are literally the only two things you gotta know about like enzyme, like anatomy, I don't know. But these are two pretty important words, so I know what they mean. Also, enzymes are affected by the temperature and pH of a cell, okay? Because basically, if you increase the temperature, right, like, more molecules are gonna collide with the enzyme and it's gonna be able to do more work, but if you make it too hot, then the enzyme can't hold itself together, so it's just gonna completely break up and that's called denaturing.
Same with pH, right, there's an optimal point for how well an enzyme does, but if you make it too acidic, it's gonna die, if you make it too basic, it's gonna die. And then one more thing that contributes to how an enzyme works is sometimes they can have, like, a particle that attaches to it, and this right here, the thing that, like, helps the enzyme function is called the cofactor if it's biological it's called the coenzyme but that's not that important don't worry about it if you don't know what the heck i'm talking about probably not going to be tested okay so now that we know how enzymes work let's talk about how they are regulated okay because like for example if there's an enzyme that destroys thing you don't want to like running rampant on the streets of new york okay so essentially there's two ways that an enzyme could be inhibited right it could be competitively inhibited where like a molecule blocks the active site right that makes sense right it's competing with the actual substrate for the site So that's why it's called a competitive inhibitor. And then you got your sad substrate just sitting out here.
This is so sad. But then if we look at a different example, there's something called a non-competitive inhibitor that like binds somewhere else. It doesn't block the site, but it makes the site close.
So now the enzyme can't even serve the substrate, and now the substrate is even more sad. Oh my god, it's crying. This is horrible.
This guy is non-competitive. And of course there's allosteric regulation which is kind of advanced and not that important But if you want to know what it is, it's literally non-competitive inhibition But you can also do it with activation like you can make an enzyme do more stuff by attaching a molecule to some other site called the allosteric site But let's get back to the relevant stuff Another cool thing that enzymes can do is let's say they're converting like A to B Now there's a ton of these enzymes and they're working their butts off and they make a ton of B and then it sounds like Come on stop being so much B What are the enzymes supposed to do? They don't just magically disappear after the B is made. Basically what cells do is they do something called feedback inhibition, okay? So essentially what happens is B inhibits the enzyme that made it.
So if you have a lot of B, your enzymes are not going to work at all, so you're going to make less B. Which makes perfect sense, right? If you have a lot of it, you don't want to make as much of it.
This right here is called feedback inhibition. Epic stuff. Okay, we are finally done with all the background information.
Let us talk about respiration and photosynthesis. Okay, now I already made a video on respiration and I think that the actual details of respiration are super super boring So i'm just going to talk about it at a really high level and just tell you how to understand So basically what respiration is is it's using oxygen, right? Like we have to breathe in oxygen to survive It basically uses oxygen to break down glucose in order to get us energy, right?
We take in a bunch of food. We have glucose in our body now Now we need some way to convert it to atp, right? Because otherwise we can't use use oxygen and glucose to make atp Literally the one way I remember the respiration equation is just by thinking, what do humans do?
They take in oxygen, we have to breathe, okay? And then we take in a bunch of junk food, okay? Oh, I might be speaking for myself.
But we take in food, okay? That's the point. And then we spit out carbon dioxide.
And then we let off a little water from you know where. I mean, that water's from other places too, but you get the point. So you got C6H12O6 is glucose, plus O2.
And that gives off carbon dioxide, right? We breathe out carbon dioxide, plus the little water that comes out, H2O. So looking at this equation, the basic steps of respiration is you break down this really big sugar into a bunch of carbon dioxide and you get energy from it somehow.
So exactly what happens is you go from glycolysis to pyruvate oxidation to the Krebs cycle to the electron transport chain. So basically in glycolysis you start with the 6 carbon sugars glucose, okay? And literally all you do in glycolysis is you chop this guy in half and you make 2 3 carbon guys. Pyruvate. And in the process you make 2 ATP, 2 NADH.
The steps of glycolics are pretty irrelevant. Then we get rid of 2 CO2 But we also make an NADH, two NADHs. So now we got rid of two carbons, okay?
So one carbon comes from the first guy, so this guy becomes a 2C. And then this guy also becomes a 2C. And these guys are acetyl-CoA. Okay, so now we move on to the next stage, okay?
So that was glycolysis, this pyruvate oxidation. Now we move on to Krebs cycle. So essentially, you take this acetyl-CoA, you take these two carbon guys.
And what you do is you literally take out both the carbons. You break it down completely. The glucose is finally out of the way. Zero carbons. zero carbon and guess where they get pooped out they get pooped out as four co2 but in the process in the krebs cycle we make even more atp and nadh fadh2 is literally just a low quality nadh not that important okay so now in all this nasty mess all we got were a couple atps and a couple nadhs that's lame now how the heck do we get the atp we literally took phosphates and put them directly on the atp right that's how we got the atp right now so that was substrate level thoughtful relation but we didn't even get that much dude we got like lame amounts of ATP from what we just did and we did so much work we completely broke down the glucose but we have a ton of these guys so how the heck do we use the NADH?
that is where the electron transport chain does come in okay and basically what the electron transfer chain is for is literally just getting as much energy as we can out of those NADHs okay so you take the NADH and now we can finally use that oxygen that was just sitting around this whole time glucose was the main star but now oxygen has its turn so essentially oxygen is down here and basically NADH lets go of an electron becomes NAD plus now we got an electron hanging up out here and oxygen pulls it right here just grabs it and snatches it but it turns out there's a bunch of turbines here basically that's the turbine god dang i could drop but basically there's a bunch of turbines right and as oxygen pulls it through these turbines they rotate right now this is not biologically sound okay there's certainly no turbines but essentially what happens is they use the energy of pulling this electron down to push protons out of the mitochondria inner matrix so essentially you get h plus ions getting pushed outside honestly this is really convoluted but basically it uses that electron to push out h plus ions and now you've got your membrane you got a bunch of h plus ions outside of it and you know that things want to go from high concentration to low concentration so these guys want to get back into the cell and the cell being the mean person it is it exploits these h plus ions okay it literally forces them to go through atp synthase molecules that make atp and hooray you got atp Basically there's a turbine in here, the H pluses push the turbine down, it makes ATP. And because the H plus ions are going through diffusion or like osmosis, it's called chemiosmosis. Essentially the process of H plus ions being pushed out and then allowed back in through these ATP synthase molecules in order to make ATP is called chemiosmosis.
It is also called oxidative phosphorylation because you're using oxygen to power the phosphorylation of ATP to ATP. So essentially you don't really need to know respiration in like super detail, you really just need to know like the big... terms right you need to know glycolysis pyruvate oxidation krebs cycle and electron transfer chain and you gotta know oxidative phosphorylation those are the main things but what happens if i don't have oxygen this is this is like discrimination only oxygen people could use this well we have something for everyone okay so essentially what fermentation is is you basically just do glycolysis right like glycolysis doesn't take any oxygen so all they do is glycolysis all day all night i don't know how they don't get bored of it but they do glycolysis and essentially it does breaking that glucose in half again and again and again and you keep getting those two ATP and two NADH but since they can't use the NADH they basically convert the NADH back to NAD plus so that they can use it again and then they repeat the process and they only take the ATP as their energy source so all you got to know about fermentation they don't use oxygen they only use glycolysis okay all right now we're trying to talk about photosynthesis your favorite type of photosynthesis and basically this is done by autotroph autotrophs are the guys who make their own food heterotrophs are the guys who have to eat other things to get food So if you know the equation for respiration, you could easily find the equation for photosynthesis just by flipping it around. So we can flip it around and we get, so you know the plants take in CO2, so obviously there's CO2. You know they need water, so they need water, okay?
And then you have to make the opposite of what respiration makes. You make C6, H12O6, and O2. So essentially what plants are doing is they're literally just storing energy in C6, H12, O6, right?
Because glucose has a ton of energy and these guys don't. Eventually they're taking in energy from light and storing it in glucose. So that suggests that there must be two parts to this, right?
They first gotta get the energy and then they gotta store the energy in glucose and guess what the energy collecting step is called That is right is light dependent because you need light to make energy. This is so sensical Oh my god, so light dependent reaction actually get the energy and essentially what they do is they yeet up an electron Okay, like when light strikes a leaf it basically excites an electron and now that this electron is excited you still go through another electron transfer chain and this pumps out a bunch of protons that makes ADP, same idea as respiration. So the first electron that's yeeted up is called the photosystem 2. The reason why it's called photosystem 2 is because it was discovered second, even though it's first in the chain, but whatever, who cares?
And then it goes to photosystem 1, and then it gets excited here again. And then it goes down here and gets put in NADPH. So hooray, we got a bunch of energy from the life-dependent- Reaction we got ATP and we got NADPH. Plants have NADPH, animals have NADH. The P just means you add a phosphate.
So then you take the energy you got and you put it into the Calvin cycle. So essentially what the Calvin cycle does is it takes carbon dioxide, it takes the energy that you already made, and it puts them together to make glucose. So essentially there's three stages right?
You fix the carbon, so carbon fixation. Then the second is reduction. Basically that just converts it into the final product of sugar that you want.
This spits out G3P. And then you have to regenerate. for the cycle to continue.
So basically what it does is it takes carbon from the air, it puts it into another sugar, that sugar splits into two, use the energy in order to make it an energetic sugar, and then you poop out a G3P. For every three carbons you put in, you get G3P. So the three means that it's three carbon, right?
So you can basically take two of these G3P and make it into glucose. Now the last thing you got to know about photosynthesis is how it evolves. So essentially what we just talked about is a completely normal way of doing it, right?
You open your stomata, you take in some CO2, you fix that CO2, and you use it to make glucose. But that is not very smart because you can only do this in the day, right? Because you're only getting energy in the day. You only have light in the day. So most plants could only do this, like, carbon fixing and everything during the day.
But what happens if it's a really hot day and you have to, like, close your stomata, right? Because otherwise you're going to lose too much water. But then you're going to have a buildup of oxygen in your leaves, right?
Because it's not using the oxygen. So eventually, a ton of oxygen is going to be left over. And then what happens is the oxygen is accidentally used and it's...
Just bad in general, okay? You don't want to have oxygen used instead of CO2 because then you're not getting any more sugars. You need carbons to make sugar.
So that right there is called photorespiration. Using O2 instead of CO2. And there may be two defenses against it. The first one is your C4 plants, like normal plants are called C3 plants. What C4 plants do is they use a different enzyme than C3 plants to fix their CO2.
So C3 plants use Rubisco, but these guys use PEP carboxylase, which doesn't even look at oxygen, okay? So it fixes it with this epic enzyme in one cell. and then it sends it over to another cell that does the calvin cycle and then cam is basically crash eletion acid metabolism and basically what those do is they open the stomata only at night okay at night you're not going to lose water so you'll never have to close your stomata and if you never have to close your stomata you're never going to have too much o2 so they store the co2 until the morning and then once in the morning they could use it with the somata closed so you're never going to have o2 as a problem because you're just going to have your stomata open all night finish all that stuff during the night and then during the day you don't have to worry about o2 at all all right so that's basically it the one last thing that's in this unit is like molecular variation i don't know what the heck that means and i looked it up and basically all they were talking about is like how chlorophyll could like change over time or how like animals or like cells adapt to different environments by changing their molecules so chlorophyll is a very good example of this because basically different chlorophyll like absorb different types of light right like most chlorophyll reflect green really well which is why you see green and they absorb red and blue light really well But if you change the lighting conditions, it might change the ratio of chlorophyll in order to get more light or whatever. That kind of thing.
So that's basically all we got to talk about for this unit. It was a pretty long unit, but it's a pretty interesting unit too. So, hope you guys enjoyed. Thank you guys so much for watching.
If you guys want more of these crash codes, just let me know down in the comments. Thank you guys for watching again. See you guys next time.