In this video, we're going to introduce glycolysis. And so glycolysis is the very first step of cellular respiration, and it involves the breakdown of a single glucose molecule into 2 pyruvate molecules. And so when we take a look at the term glycolysis, you'll find these two roots embedded. You'll find the root glyco and you'll find the root lysis. And so the root glyco is a root that means sugar, and so glucose is indeed a sugar. And of course the root lysis is a root that means to break down. And so when you put these two roots together, glyco and lysis, you get glycolysis, which means really breaking down a sugar or breaking down specifically glucose. And glucose is gonna get broken down into 2 pyruvate molecules. So let's take a look at our image down below here at glycolysis and notice that it starts with a single glucose molecule and it ends with 2 pyruvate molecules, just as we indicated up above. Now it's very important to note that glucose has a total of 6 carbon atoms, And so notice that down below we're representing glucose as these 6 black circles, and each of these black circles represents one of the carbon atoms found in glucose. Now glucose does have other types of atoms as well, but when your text books and professors are talking about cellular respiration, they mainly tend to focus on the carbon atoms of glucose. And so the glucose here starts with 6 carbon atoms. And at the end of cellular respiration I'm sorry, at the end of glycolysis, notice that the glucose molecule was broken apart into 2 pyruvate molecules, each with 3 carbon atoms. So here we have 1 pyruvate molecule and here we have a second pyruvate molecule. Now it's important to note that as we move forward with aerobic cellular respiration, all 6 of the carbon atoms that were originally found in glucose are all going to end up being converted to carbon dioxide or c o 2. And this is specifically going to happen in the 2nd and third steps of cellular respiration. So this is something to look forward to as we move forward in our course, that all of the glucose molecules, carbon atoms are all going to eventually end up as carbon dioxide. And that carbon dioxide is ultimately gonna end up getting exhaled or, breathed out into the environment. Now glycolysis is the only step of aerobic cellular respiration that occurs outside of the mitochondria in the cell's cytoplasm. And so, this is very important to note. And it's also glycolysis is also the only stage of cell cellular respiration that does not require oxygen, and so that's also a very important key feature to remember about glycolysis. Glycolysis can occur in both the presence and the absence of oxygen, and that is not the case with all of the other stages of cellular respiration. So notice down below in our image here we have the process of glycolysis here in this box which takes a single glucose molecule with 6 carbon atoms and breaks it up into 2 pyruvate molecules each with 3 carbon atoms. And notice that the process of glycolysis is occurring on the outside of the mitochondria. So here we have the mitochondria, but glycolysis occurs on the outside of the mitochondria. And it's the only stage of aerobic cellular respiration that occurs outside of the mitochondria. All of the other stages occur inside of the mitochondria. And once again glycolysis is the only stage that does not require oxygen. Now here down below, notice that we're saying that glycolysis occurs, once again, outside mitochondria, specifically in the cell's cytoplasm. So the location of glycolysis is definitely an important feature to remember because glycolysis occurs outside of the mitochondria in the cell cytoplasm, and all of the other stages occur inside of the mitochondria. Now this here concludes our brief introduction to glycolysis and we'll continue to talk more and more about glycolysis as we move forward here in our course. So I'll see you all in our next video.
2
Problem
Problem
Where does the first stage of aerobic cellular respiration take place within a cell?
a) Mitochondrial matrix.
b) Inner mitochondrial membrane.
c) Intermembrane space.
d) Cytoplasm.
A
Mitochondrial matrix.
B
Inner mitochondrial membrane.
C
Intermembrane space.
D
Cytoplasm.
3
concept
Phases of Glycolysis
Video duration:
6m
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Video transcript
In this video, we're going to introduce the phases of glycolysis. And so it turns out that glycolysis actually consists of a series of a total of 10 chemical reactions. And these 10 chemical reactions that make up glycolysis can actually be grouped into 2 phases. Now in this video we're not really going to focus on the 10 reactions so much, but we are going to focus on how these 10 reactions are grouped into 2 phases, and we're really gonna be focusing on the 2 phases of glycolysis. Now, the first phase of glycolysis is called the energy investment investment phase, and the 2nd phase of glycolysis is called the energy harvest phase. And so notice that the energy investment phase up above is color coordinated to the energy investment phase down below, and the energy harvest phase is color coordinated to the energy harvest phase down below. And so notice in this image down below, really what we're showing you is glycolysis. Notice that it's starting with a single glucose molecule that has 6 carbon atoms, and it breaks down that glucose into 2 pyruvate molecules each with 3 carbon atoms. And so this whole green box represents glycolysis, but once again glycolysis occurs in 2 phases, the energy investment phase and the energy harvest phase. And so the energy investment phase, as its name implies with the investment, is going to require an investment of energy or an input of energy by using 2 ATP molecules. Now this is a little bit ironic because if you recall from our previous lesson videos, the whole point of aerobic cellular respiration is to make a lot of ATP. That's the whole point of aerobic cellular respiration, to make a lot of ATP. But the very first stage of aerobic cellular respiration, glycolysis, the very first thing that happens is that it does not make ATP, but it uses ATP. That's a little bit ironic. However, it turns out that this is just an investment of the ATP because by inputting 2 ATP molecules the cell is able to transition into the second phase of glycolysis which is the energy harvesting phase. And as its name implies it's going to harvest energy or produce energy, specifically by forming 2 NADH molecules and 4 ATP molecules. And so if we take a look at our image down below at glycolysis, notice that the first phase of glycolysis, the energy investment phase, is actually going to use 2 ATPs and that is using some of the cell's energy. However, this is just an energy investment because after the cell utilizes those 2 ATPs, it can transition into the next phase here which is the energy harvest phase. And the energy harvest phase notice produces 2 electron carriers, specifically 2 NADH molecules, and it also produces a total of 4 ATP molecules. Now, if we're looking at the net products from 1 single glucose molecule, then what we'll see is that not only are 2 pyruvates formed and 2 NADH are formed, but there's also a net of 2 ATP molecules that are formed. But wait a second, Jason. I thought you said that there were 4 ATP molecules that were made, not 2 ATP molecules. Well, what we need to remember is that 2 ATP molecules were being used up in the energy investment phase. So because 2 ATP molecules were used up, of the 4 ATP molecules that are being made, 2 of them are just making up for the 2 that were invested. And so really there's just a net of 2 ATP molecules made. And so notice if we take a look at this part of our image down below right here, we're reminding you that the energy harvesting phase does produce a total of 4 ATPs, as we indicated right here. However, we can't forget that the energy investment phase burns or uses 2 ATPs. So we have to subtract off those 2 ATPs from the total. And so that gives us a total net of 2 ATP molecules produced during glycolysis, 2 net ATPs made. And so an easy way to be able to remember that there's 2 net ATP made during glycolysis is to remember that the net products from 1 glucose molecule are just double. You get not only 2 pyruvates, but also 2 NADH, and also 2 net ATP molecules. Now these 2 pyruvates that are end up, forming at the end of glycolysis, they end up getting transported to the mitochondrial matrix. Basically getting transported to the mitochondria so that the next step of cellular respiration can take place. And so notice that here glycolysis occurs once again on the outside of the mitochondria and it ends up producing 2 NADH, a net of 2 ATPs, and 2 pyruvates. And so these 2 pyruvates are going to make their way to the mitochondria and into the mitochondrial matrix. And so this here concludes our introduction to the phases of glycolysis, and we'll be able to get some practice applying these concepts as we move forward in our course. So I'll see you all in our next video.
4
concept
Remembering Phases of Glycolysis
Video duration:
2m
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Video transcript
In this video, what we have is a silly memory tool for helping you with remembering the phases of glycolysis. And so when it comes to the phases of glycolysis, you can remember that Gary invests to harvest his profits and travel to Mexico. And so if you can remember that Gary invests to harvest his province and travel to Mexico then hopefully that can help you remember these phases of glycolysis. And so the g in Gary here can help you remember that the process of glycolysis starts with a glucose molecule which has 6 carbons, represented by these 6 black circles that you see here. And then the I in invest is going to stand for the I in the investment phase which is the very first phase of glycolysis where the cell needs to invest 2 ATP molecules in order to get the process of glycolysis started. Then the h in harvest is going to stand for the h in the harvest phase of glycolysis, which is the second phase of glycolysis where the cell can double the amount of energy that it invested and so it's able to produce 4 ATPs and a total net of 2 ATPs since it had to invest 2 ATPs to begin with. Then the p in profits is going to stand for the p in pyruvate because this is ultimately what the process of glycolysis ends with, the formation of 2 3 carbon pyruvate molecules. So you can see those 2 3 carbon pyruvates highlighted here. And then once these pyruvates have been formed the process of glycolysis is over. So you can see here that the process of glycolysis is indicated by this green box. And what needs to happen is these 2 pyruvates that were formed, they need to travel to the mitochondria. And so that is where this Mexico comes into place. So traveling to Mexico represents traveling, the pyruvates traveling to the mitochondria. And so that is where the second, stage of cellular respiration will take place. And so, notice here what we have in this image is a mitochondria that is chilling on the beach in Mexico, sipping on some pina coladas or something like that. And so hopefully, this little memory tool here, Gary Invest to harvest his profits and travel to Mexico can help you with remembering the phases of glycolysis. And so that being said, we'll be able to apply some of these concepts moving forward. So I'll see you all in our next video.
5
example
Glycolysis Example 1
Video duration:
1m
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Video transcript
So here we have an example problem that wants us to fill in the blank here using one of these 5 potential answer options down below. And the example problem says there is an energy investment step needed to get glycolysis started requiring the use of blank ATPs. And once again we've got these 5 potential answer options down below. And so what we need to recall is that glycolysis has 2 phases. The energy investment phase and the energy harvest phase. The energy investment phase requires an investment of 2 ATPs, and so really that's what this example problem is getting at. In order for the energy investment step to occur, it requires the use of 2 ATPs. And so the correct answer here is going to be answer option a. Now, after the the 2 ATPs have been used, then the cell can transition to the 2nd phase of glycolysis, which is the energy harvest phase. And the energy harvest phase produces a total of 4 ATPs and 2 NADH. And of those 4 ATPs, because 2 of them got burnt, ultimately it's only a net of 2 ATPs that are made. But once again in terms of the energy that needs to be invested, it's 2 ATPs that need to be invested. So the correct answer to this example is answer option a, and that concludes this example. So I'll see you all in our next video.
6
Problem
Problem
Starting with one molecule of glucose, glycolysis results in the net production of which of the following sets of energy-containing products?
a) 2 NAD+, 2 pyruvate, and 2 ATP.
b) 2 NADH, 2 pyruvate, and 2 ATP.
c) 4 NADH, 2 pyruvate, and 4 ATP.
d) 6 CO2, 2 pyruvate, and 2 ATP.
A
2 NAD+, 2 pyruvate, and 2 ATP.
B
2 NADH, 2 pyruvate, and 2 ATP.
C
4 NADH, 2 pyruvate, and 4 ATP.
D
6 CO2, 2 pyruvate, and 2 ATP.
7
Problem
Problem
Which of the following is a result of glycolysis?
a) A net gain of four ATP per one glucose molecule.
b) Conversion of FAD to FADH2.
c) Conversion of one glucose molecule to two pyruvate molecules.
d) Conversion of NADH to NAD+.
A
A net gain of four ATP per one glucose molecule.
B
Conversion of FAD to FADH2.
C
Conversion of one glucose molecule to two pyruvate molecules.