Understanding Cellular Respiration Process

Okay, so the topic of this video is cellular respiration. Let's go ahead and get started. So right here, this molecule, adenosine triphosphate, this is why the cell performs cellular respiration. It's trying to make this because ATP is the energy molecule used by the cell. You'll often hear ATP as an analogy compared to money or the currency of a cell because, you know, we spend money on goods and services. and the cell will spend ATP to perform, you know, these reactions and many others that I did not list. But here's the triphosphate part. Notice how there are three phosphates, and they're in the bonds of these three phosphates, particularly between the second and third phosphate is energy. And in the hydrolysis of ATP, if you've forgotten that hydro means water and lysis means to break down, So in the breakdown of ATP, ATP with water will yield a DP, a single phosphate, and energy, and it's this energy that will power the cell. And so in this very simplified diagram of an ATP molecule, here comes water, and my scissors represent the actions of an enzyme, and that third phosphate tends to be broken off, and in that, Energy is released and it's this energy that will often drive the cellular processes that you see listed in the notes. So how is this molecule of ATP created? Well, ATP gets created through cellular respiration. Cells need ATP to power their chemical reactions. And most ATP gets produced by the powerhouse of the cell, the mitochondria. The powerhouse because it produces the ATP power. Now ATP is created through this process of cellular respiration which we're going to go through in the rest of this video. And what happens is a molecule of glucose that we get from our food is going to be broken down to make a whole bunch of molecules of ATP. That's what happens during the the process of cellular respiration. Glycolysis, the Krebs cycle, the electron transport chain, these are all breaking down molecules of glucose from our food to to produce ATP. So let's move into glycolysis. Okay, starting with glycolysis, the location takes place in the cytoplasm of a cell and what happens is that blue hexagon ring labeled glucose. Glucose is going to be broken down by molecules of ATP, a molecule called NAD, and various enzymes. Now for simplicity, I've only drawn the six carbons of glucose in my diagram. But glucose, you can see, also has 12 hydrogens and 6 oxygens. So what happens is two molecules of ATP plus enzymes are going to begin to break down glucose. Now this might seem a little counterproductive using ATP to make ATP, but Keep in mind the goal is to make a lot of ATP. So if you have to spend a little bit of ATP to make a lot of ATP, it's worth it. So a molecule of ATP plus the scissors representing an enzyme will begin to break down glucose into this intermediate molecule here. So next, another molecule of ATP and a different enzyme will be broken down. and the energy from ATP will break that intermediate down into two molecules labeled PGAL or phosphoglyceraldehyde. Now, PGAL itself, this is another intermediate. It will be broken down further in a moment. So, next, enzymes, which are in the cytoplasm, will add another phosphate onto each of the PGALs. So, here's an enzyme, the scissors, adding a phosphate to the PGAL on the left, and and the phosphate being added to the PGAL on the right. And by doing this, this converts the PGAL into another intermediate molecule. So next, a couple molecules called NADH are going to be created and will enter the mitochondria. Well, they begin as molecules called of NAD. NAD is an abbreviation for nicotinamide adenine dinucleotide. And what happens, of course, there's enzymes involved. NAD with the help of an enzyme will strip off a hydrogen to create NADH. NADH can be looked at as a hydrogen carrier, carries the hydrogen over to the mitochondria. The same thing happens with the other NAD. An enzyme will help to strip off a hydrogen and NADH will carry that hydrogen over to the mitochondria. These are going to be very, very important when we get to the electron transport chain. So now that we're near the end of glycolysis, let's talk about how four molecules of ATP are created. You see those four yellow circles with the P? Those each represent a phosphate group. And what happens is here's four molecules of ADP. And ADP, along with the help of an enzyme, will strip off one of those phosphates to create a molecule of ATP. Now this happens three more times. And ADP with the help of an enzyme will strip off one of those phosphates to make ATP. ADP strips off a phosphate to make ATP. And ADP, again, strips off a phosphate with the help of enzymes to make ATP. And what we're left with, what was once glucose, is now these two molecules called pyruvates. And the pyruvates are going to be very useful in the Krebs cycle coming up. We also have a... total amount of 4 ATP molecules created, although sometimes you'll hear it referred to as a net gain of 2 ATPs. Well, what do we mean by that? Well, 4 ATPs were created, but 2 ATPs were used to start the process of glycolysis, so when you subtract the 2 at the start from the 4 that were created, that's what we mean by a net gain. Well, what happens next? Well, what happens next depends upon the type of cell and the conditions that the cell is within. There's two possible pathways. Both of them are going to involve those pyruvates. Those pyruvates are going to be broken down even further. The pathway that we're going to follow in these notes is the aerobic pathway with oxygen leading to the Krebs cycle in the electron transport chain. But if oxygen is lacking, if a cell is in an anaerobic environment, Those pyruvates will be used in fermentation. I have a different video if you want to learn about fermentation, but this video is going to follow the aerobic pathway. So here we are back at our cell. Glycolysis has just completed itself and we're about to start the Krebs cycle. And so the two molecules of pyruvate will migrate into the mitochondria. So let's go into the mitochondria and take a closer look. And when we zoom into the mitochondria, so there's the two pyruvates. Notice how they're in the mitochondrial matrix, the inner, inner fluid layer of the mitochondria. And so what happens is we're going to follow the pyruvate on the left. Now, the same thing happens to the pyruvate on the right, but for simplicity, we're going to just follow the one on the left. The pyruvate is going to be broken down into acetic acid. In the process of doing this, NADH is going to be created. So there's a molecule of NAD. When pyruvate is being broken down, NAD will come and strip off a hydrogen to make NADH. Notice how some carbon dioxide was created as well. That's just waste. What we're left with is acetic acid, acetic acid being an intermediate molecule. What happens next is a really large molecule that I'm being very simplistic in just drawing it and labeling it CoA. Coenzyme A, a really large molecule, will bond to acetic acid. Well, how big is coenzyme A? Well, look at the formula of acetic acid. When we bond coenzyme A, we form acetyl-CoA. Look at how large that formula is. So, acetyl-CoA is also an intermediate molecule. It's just the next step of the Krebs cycle. What happens to the acetyl-CoA, the third step, and this is where the Krebs cycle also gets its name of the citric acid cycle. Acetyl-CoA is going to be converted and broken down into citric acid. That happens when a four carbon molecule from the previous Krebs cycle bonds to the acetyl-CoA. And I have it flashing for a reason. I hope you all understand why it's flashing when we get to the end. I wanted to do something for you to remember this four carbon molecule. from the previous Krebs cycle. So an enzyme will bond that four carbon molecule to the acetyl CoA and the Coenzyme A breaks away and what you're left with is citric acid. Citric acid being a six carbon molecule. Okay, so the six carbon citric acid will be broken down into a five carbon molecule and in the process of doing this, NADH is created. So here's a molecule of NAD. NAD along with an enzyme will help to break down the citric acid. Notice how NADH was created. Also, some carbon dioxide waste was generated. This is why citric acid went from a 6-carbon to a 5-carbon molecule. So what about this 5-carbon molecule? This 5-carbon molecule is again an intermediate. It's going to be broken down into a 4-carbon molecule, and in the breakdown, a couple things happen. Number one, another molecule of NADH is created. So there's NAD. With the help of an enzyme, NAD will strip off a hydrogen. But that's not the only thing that happens. A molecule of ATP will be created because... the matrix of the mitochondria there are various solutes and molecules dissolved within the matrix and here's a molecule of ADP and a phosphate enzymes bring these molecules together and in the breakdown of this five carbon molecule into a four carbon molecule the ATP is bonded together and also in the act of doing this carbon dioxide waste is created. So that's how it goes from a five carbon to a four carbon molecule. Now this four carbon molecule is again an intermediate. Enzymes will rearrange the four carbon molecule into another four carbon molecule. And in the process of doing this, a molecule of NADH is created. That means we have to have NAD come along and strip off a hydrogen. And then another molecule very similar to NAD called FAD is going to come on in and strip off not one, but two hydrogens forming FADH2. Now, all of these NADHs and this FADH2, they have a role to play. We just haven't seen it yet. Their role is coming up in a few moments. Well, what happens with this four-carbon molecule that's just been rearranged? Notice how it's flashing now. That's because this is the same flashing 4-carbon molecule we saw earlier. Remember the Krebs cycle is a cycle. So I wanted to do something for you to realize when the Krebs cycle was beginning its next turn. And what happens with this 4-carbon molecule? It will bond with acetyl CoA, that really big molecule we saw earlier. So enzymes will bind it together, the CoA breaks away, and what we're left with is the 6-carbon molecule known as citric acid, and the process repeats itself. Well, when we look at what's created an overview of the Krebs cycle, this always frustrated me because I always thought that, you know, cellular respiration's purpose is to make a lot of ATP, and only two molecules of ATP were created. One molecule of ATP from the pyruvate on the left, one molecule of ATP from the pyruvate on the right. But the big prize the Krebs cycles, not the two molecules of ATP, it's all the NADH and FADH2 that was created. Those are really important in the electron transport chain. So let's look at that next. So as we move on into the electron transport chain, what we're going to do is we're going to zoom in to the membrane of the matrix. And when we zoom on in, here we are. So now that we've zoomed in, we can see Embedded in the inner mitochondrial membrane are some gray tubes and cylinders. These are symbolic of the protein complexes that are embedded inside this membrane here. And these are going to help to kind of drive the electron transport chain. And we're going to see why all the NADH and FADH2 was created. Well, here's a molecule of NADH. Enzymes, of course, are going to help break this down. And notice how... A couple of electrons are now embedded in the inner mitochondrial membrane, and one of the hydrogen ions has positioned itself at one of those protein tubes. Well, this happens repeatedly. Another NADH is broken down, a couple more electrons embed in the inner mitochondrial membrane, another hydrogen is positioned itself at one of the protein tubes. And here's an FADH2 that's broken down, and what we're seeing is... The beginning of the electron transport chain, those electrons are going to start a chain reaction, which we call the electron transport chain. Well, what happens with these electrons? This is why it's called the electron transport chain. These electrons are going to start a chain reaction of events where those hydrogens are going to be transported out of the matrix. And so the electrons, as they transfer from... protein channel to protein channel to protein channel, as they transfer from the protein channels, they provide the energy to pull these hydrogens out of the matrix, and this will set up the next step of the electron transport chain. So once all the hydrogens have been pulled out of the matrix, they have accumulated in a very large amount now, and this is going to lead to really rapid diffusion through the molecule labeled ATP synthase. And so those hydrogen ions are going to activate this enzyme, this molecule called ATP synthase. And notice how ATP synthase has an ADP and a P attached to it. They just need the ATP synthase just need something to bond the phosphate with the ADP and that's the job of the hydrogen ion. So what the hydrogen does is it loads itself into ATP synthase, simple diffusion from a high concentration to a low and as the hydrogen diffuses through the mechanical forces bring together the ADP and the P to create ATP. And this happens repeatedly over and over and over. So here's another ADP and another phosphate. Here's another hydrogen and as the hydrogen diffuses through, ATP is created. And this happens repeatedly over and over and over up to 34 times. Well, as we wind down, notice how there are some hydrogens and electrons that are now regathering inside the matrix. There has to be a way to clean these up in order to keep the process moving. And this is where the water is formed. If you look at the chemical formula of cellular respiration, one of the products that's formed is water. Well, oxygen from the air that we breathe will bond with two of the hydrogens and two of the electrons to form a molecule of water. This is... where we get the water in the chemical reaction of cellular respiration. It comes from the end of the electron transport chain. So if you're in my class, we'll talk about this essay in more detail. Well, as I wrap this up, I want to thank you for watching and, you know, pause the video here, try to answer these questions for review practice, and, you know, leave your comments in the box below. Thanks for watching. Thank

Okay, so the topic of this video is cellular respiration. Let's go ahead and get started. So right here, this molecule, adenosine triphosphate, this is why the cell performs cellular respiration.

It's trying to make this because ATP is the energy molecule used by the cell. You'll often hear ATP as an analogy compared to money or the currency of a cell because, you know, we spend money on goods and services. and the cell will spend ATP to perform, you know, these reactions and many others that I did not list.

But here's the triphosphate part. Notice how there are three phosphates, and they're in the bonds of these three phosphates, particularly between the second and third phosphate is energy. And in the hydrolysis of ATP, if you've forgotten that hydro means water and lysis means to break down, So in the breakdown of ATP, ATP with water will yield a DP, a single phosphate, and energy, and it's this energy that will power the cell. And so in this very simplified diagram of an ATP molecule, here comes water, and my scissors represent the actions of an enzyme, and that third phosphate tends to be broken off, and in that, Energy is released and it's this energy that will often drive the cellular processes that you see listed in the notes.

So how is this molecule of ATP created? Well, ATP gets created through cellular respiration. Cells need ATP to power their chemical reactions. And most ATP gets produced by the powerhouse of the cell, the mitochondria. The powerhouse because it produces the ATP power.

Now ATP is created through this process of cellular respiration which we're going to go through in the rest of this video. And what happens is a molecule of glucose that we get from our food is going to be broken down to make a whole bunch of molecules of ATP. That's what happens during the the process of cellular respiration. Glycolysis, the Krebs cycle, the electron transport chain, these are all breaking down molecules of glucose from our food to to produce ATP. So let's move into glycolysis.

Okay, starting with glycolysis, the location takes place in the cytoplasm of a cell and what happens is that blue hexagon ring labeled glucose. Glucose is going to be broken down by molecules of ATP, a molecule called NAD, and various enzymes. Now for simplicity, I've only drawn the six carbons of glucose in my diagram.

But glucose, you can see, also has 12 hydrogens and 6 oxygens. So what happens is two molecules of ATP plus enzymes are going to begin to break down glucose. Now this might seem a little counterproductive using ATP to make ATP, but Keep in mind the goal is to make a lot of ATP.

So if you have to spend a little bit of ATP to make a lot of ATP, it's worth it. So a molecule of ATP plus the scissors representing an enzyme will begin to break down glucose into this intermediate molecule here. So next, another molecule of ATP and a different enzyme will be broken down.

and the energy from ATP will break that intermediate down into two molecules labeled PGAL or phosphoglyceraldehyde. Now, PGAL itself, this is another intermediate. It will be broken down further in a moment.

So, next, enzymes, which are in the cytoplasm, will add another phosphate onto each of the PGALs. So, here's an enzyme, the scissors, adding a phosphate to the PGAL on the left, and and the phosphate being added to the PGAL on the right. And by doing this, this converts the PGAL into another intermediate molecule. So next, a couple molecules called NADH are going to be created and will enter the mitochondria. Well, they begin as molecules called of NAD.

NAD is an abbreviation for nicotinamide adenine dinucleotide. And what happens, of course, there's enzymes involved. NAD with the help of an enzyme will strip off a hydrogen to create NADH.

NADH can be looked at as a hydrogen carrier, carries the hydrogen over to the mitochondria. The same thing happens with the other NAD. An enzyme will help to strip off a hydrogen and NADH will carry that hydrogen over to the mitochondria. These are going to be very, very important when we get to the electron transport chain. So now that we're near the end of glycolysis, let's talk about how four molecules of ATP are created.

You see those four yellow circles with the P? Those each represent a phosphate group. And what happens is here's four molecules of ADP. And ADP, along with the help of an enzyme, will strip off one of those phosphates to create a molecule of ATP. Now this happens three more times.

And ADP with the help of an enzyme will strip off one of those phosphates to make ATP. ADP strips off a phosphate to make ATP. And ADP, again, strips off a phosphate with the help of enzymes to make ATP. And what we're left with, what was once glucose, is now these two molecules called pyruvates. And the pyruvates are going to be very useful in the Krebs cycle coming up.

We also have a... total amount of 4 ATP molecules created, although sometimes you'll hear it referred to as a net gain of 2 ATPs. Well, what do we mean by that? Well, 4 ATPs were created, but 2 ATPs were used to start the process of glycolysis, so when you subtract the 2 at the start from the 4 that were created, that's what we mean by a net gain.

Well, what happens next? Well, what happens next depends upon the type of cell and the conditions that the cell is within. There's two possible pathways. Both of them are going to involve those pyruvates. Those pyruvates are going to be broken down even further.

The pathway that we're going to follow in these notes is the aerobic pathway with oxygen leading to the Krebs cycle in the electron transport chain. But if oxygen is lacking, if a cell is in an anaerobic environment, Those pyruvates will be used in fermentation. I have a different video if you want to learn about fermentation, but this video is going to follow the aerobic pathway. So here we are back at our cell.

Glycolysis has just completed itself and we're about to start the Krebs cycle. And so the two molecules of pyruvate will migrate into the mitochondria. So let's go into the mitochondria and take a closer look. And when we zoom into the mitochondria, so there's the two pyruvates.

Notice how they're in the mitochondrial matrix, the inner, inner fluid layer of the mitochondria. And so what happens is we're going to follow the pyruvate on the left. Now, the same thing happens to the pyruvate on the right, but for simplicity, we're going to just follow the one on the left. The pyruvate is going to be broken down into acetic acid. In the process of doing this, NADH is going to be created.

So there's a molecule of NAD. When pyruvate is being broken down, NAD will come and strip off a hydrogen to make NADH. Notice how some carbon dioxide was created as well.

That's just waste. What we're left with is acetic acid, acetic acid being an intermediate molecule. What happens next is a really large molecule that I'm being very simplistic in just drawing it and labeling it CoA. Coenzyme A, a really large molecule, will bond to acetic acid. Well, how big is coenzyme A?

Well, look at the formula of acetic acid. When we bond coenzyme A, we form acetyl-CoA. Look at how large that formula is.

So, acetyl-CoA is also an intermediate molecule. It's just the next step of the Krebs cycle. What happens to the acetyl-CoA, the third step, and this is where the Krebs cycle also gets its name of the citric acid cycle. Acetyl-CoA is going to be converted and broken down into citric acid.

That happens when a four carbon molecule from the previous Krebs cycle bonds to the acetyl-CoA. And I have it flashing for a reason. I hope you all understand why it's flashing when we get to the end.

I wanted to do something for you to remember this four carbon molecule. from the previous Krebs cycle. So an enzyme will bond that four carbon molecule to the acetyl CoA and the Coenzyme A breaks away and what you're left with is citric acid. Citric acid being a six carbon molecule. Okay, so the six carbon citric acid will be broken down into a five carbon molecule and in the process of doing this, NADH is created.

So here's a molecule of NAD. NAD along with an enzyme will help to break down the citric acid. Notice how NADH was created. Also, some carbon dioxide waste was generated. This is why citric acid went from a 6-carbon to a 5-carbon molecule.

So what about this 5-carbon molecule? This 5-carbon molecule is again an intermediate. It's going to be broken down into a 4-carbon molecule, and in the breakdown, a couple things happen. Number one, another molecule of NADH is created.

So there's NAD. With the help of an enzyme, NAD will strip off a hydrogen. But that's not the only thing that happens. A molecule of ATP will be created because...

the matrix of the mitochondria there are various solutes and molecules dissolved within the matrix and here's a molecule of ADP and a phosphate enzymes bring these molecules together and in the breakdown of this five carbon molecule into a four carbon molecule the ATP is bonded together and also in the act of doing this carbon dioxide waste is created. So that's how it goes from a five carbon to a four carbon molecule. Now this four carbon molecule is again an intermediate.

Enzymes will rearrange the four carbon molecule into another four carbon molecule. And in the process of doing this, a molecule of NADH is created. That means we have to have NAD come along and strip off a hydrogen.

And then another molecule very similar to NAD called FAD is going to come on in and strip off not one, but two hydrogens forming FADH2. Now, all of these NADHs and this FADH2, they have a role to play. We just haven't seen it yet. Their role is coming up in a few moments. Well, what happens with this four-carbon molecule that's just been rearranged?

Notice how it's flashing now. That's because this is the same flashing 4-carbon molecule we saw earlier. Remember the Krebs cycle is a cycle.

So I wanted to do something for you to realize when the Krebs cycle was beginning its next turn. And what happens with this 4-carbon molecule? It will bond with acetyl CoA, that really big molecule we saw earlier.

So enzymes will bind it together, the CoA breaks away, and what we're left with is the 6-carbon molecule known as citric acid, and the process repeats itself. Well, when we look at what's created an overview of the Krebs cycle, this always frustrated me because I always thought that, you know, cellular respiration's purpose is to make a lot of ATP, and only two molecules of ATP were created. One molecule of ATP from the pyruvate on the left, one molecule of ATP from the pyruvate on the right.

But the big prize the Krebs cycles, not the two molecules of ATP, it's all the NADH and FADH2 that was created. Those are really important in the electron transport chain. So let's look at that next. So as we move on into the electron transport chain, what we're going to do is we're going to zoom in to the membrane of the matrix. And when we zoom on in, here we are.

So now that we've zoomed in, we can see Embedded in the inner mitochondrial membrane are some gray tubes and cylinders. These are symbolic of the protein complexes that are embedded inside this membrane here. And these are going to help to kind of drive the electron transport chain. And we're going to see why all the NADH and FADH2 was created. Well, here's a molecule of NADH.

Enzymes, of course, are going to help break this down. And notice how... A couple of electrons are now embedded in the inner mitochondrial membrane, and one of the hydrogen ions has positioned itself at one of those protein tubes.

Well, this happens repeatedly. Another NADH is broken down, a couple more electrons embed in the inner mitochondrial membrane, another hydrogen is positioned itself at one of the protein tubes. And here's an FADH2 that's broken down, and what we're seeing is...

The beginning of the electron transport chain, those electrons are going to start a chain reaction, which we call the electron transport chain. Well, what happens with these electrons? This is why it's called the electron transport chain.

These electrons are going to start a chain reaction of events where those hydrogens are going to be transported out of the matrix. And so the electrons, as they transfer from... protein channel to protein channel to protein channel, as they transfer from the protein channels, they provide the energy to pull these hydrogens out of the matrix, and this will set up the next step of the electron transport chain. So once all the hydrogens have been pulled out of the matrix, they have accumulated in a very large amount now, and this is going to lead to really rapid diffusion through the molecule labeled ATP synthase.

And so those hydrogen ions are going to activate this enzyme, this molecule called ATP synthase. And notice how ATP synthase has an ADP and a P attached to it. They just need the ATP synthase just need something to bond the phosphate with the ADP and that's the job of the hydrogen ion.

So what the hydrogen does is it loads itself into ATP synthase, simple diffusion from a high concentration to a low and as the hydrogen diffuses through the mechanical forces bring together the ADP and the P to create ATP. And this happens repeatedly over and over and over. So here's another ADP and another phosphate. Here's another hydrogen and as the hydrogen diffuses through, ATP is created.

And this happens repeatedly over and over and over up to 34 times. Well, as we wind down, notice how there are some hydrogens and electrons that are now regathering inside the matrix. There has to be a way to clean these up in order to keep the process moving.

And this is where the water is formed. If you look at the chemical formula of cellular respiration, one of the products that's formed is water. Well, oxygen from the air that we breathe will bond with two of the hydrogens and two of the electrons to form a molecule of water.

This is... where we get the water in the chemical reaction of cellular respiration. It comes from the end of the electron transport chain.

So if you're in my class, we'll talk about this essay in more detail. Well, as I wrap this up, I want to thank you for watching and, you know, pause the video here, try to answer these questions for review practice, and, you know, leave your comments in the box below. Thanks for watching.

Thank

Transcript for:Understanding Cellular Respiration Process

Transcript for:
Understanding Cellular Respiration Process