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Lecture Comments (21)

1 answer

Last reply by: Bryan Cardella
Sun Jan 7, 2018 4:23 PM

Post by Yuyun Kusuma on January 7 at 09:34:22 AM

Hello, first of all, thanks for the all the video lessons you've made. All of them are interesting and informative. I've already watched some of them. But actually I don't know why a few months ago, I could watch all of educator's videos easily without much buffering, while recently, the "buffering" has been very often, in fact, and it occurs every a few seconds... I know my internet connection here is a bit slow, but still I can watch many videos on youtube, but not even 1 here.

1 answer

Last reply by: Bryan Cardella
Sat Mar 18, 2017 4:21 PM

Post by Kapil Patel on March 17, 2017

where are oxidative phosphorlation located in what type cells animals cells or plant cells

5 answers

Last reply by: Bryan Cardella
Thu Oct 20, 2016 11:34 AM

Post by Lydia Radden on October 16, 2016

Pro. Cardella you stated we get sugars from the plants we eat which our cells convert into energy. We being omnivores, however what about carnivores how do their cells process sugars into energy. Meaning which food product do they eat to get the sugars needed to convert to energy.

1 answer

Last reply by: Bryan Cardella
Fri Jun 24, 2016 2:12 PM

Post by Scott Pearce on June 24, 2016

Sorry to Bother you, I have attended the University Of Minnesota Crookston. I understand you might not know in detail what is required in the general Biology course there if you have not been there. But Do you think I might be required to know in detail to which you have shown for Photosynthesis and  aerobic respiration. for example to know the different names for the sugars in Glycolosis ( Glucose, fru 1,6-DP) and where atp is used and where NADH is used ?

2 answers

Last reply by: Scott Pearce
Wed Jun 22, 2016 8:46 AM

Post by Scott Pearce on June 11, 2016

sorry to bother you but from one kreb cycle couldn't you get 4 NADH, i think you say 3

5 answers

Last reply by: Bryan Cardella
Thu Feb 12, 2015 5:55 PM

Post by Carroll Fields on February 10, 2015

Prof. Cardella can you please recommend an excellent book that we can use to study biology concepts( some Gen. & AP Bio), to greater conceptually understanding and in preparation for the AP Bio exam.
     Also I live near the DC area in Maryland, and am a homeschooled high school student. I am looking for Biology and Chemistry labs, and was wondering if you had any suggestions.

Thank You,

1 answer

Last reply by: Bryan Cardella
Mon Oct 13, 2014 3:25 PM

Post by A K on October 13, 2014

Thank you! Your lectures are really helpful.

Question: How does the cell determine whether the pyruvate will go through either the anaerobic or aerobic respiration?

We discussed this in class briefly, but I had difficulty understanding.

1 answer

Last reply by: Bryan Cardella
Fri Jun 27, 2014 1:44 AM

Post by David Gonzalez on June 26, 2014

In Glycolysis, the two electron carriers pick up the electrons/protons from the two G3P molecules? Thanks.

Cellular Energy, Part II

Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.

  • Intro 0:00
  • Aerobic Respiration 0:05
    • Process of Breaking Down Carbohydrates to Make ATP
    • Glycolysis
    • Krebs Cycle
    • Oxidative Phosphorylation
    • Produces About 36 ATP
  • Glycolysis 3:35
    • Breakdown of Sugar Into Pyruvates
    • Occurs in the Cytoplasm
  • Krebs Cycle 11:40
    • Citric Acid Cycle
    • Acetyl-CoA
    • How Pyruvate Gets Modified into acetyl-CoA
  • Oxidative Phosphorylation 22:45
  • Anaerobic Respiration 29:44
    • Lactic Acid Fermentation
    • Alcohol Fermentation
    • Produces Only the ATP From Glycolysis
  • Aerobic Respiration vs. Photosynthesis 36:43

Transcription: Cellular Energy, Part II

Hi, welcome back to, this is the lesson on cellular energy, continued.0000

This is the second part of cellular energy, the first part was about energy in general, pertaining to life and photosynthesis.0006

Photosynthesis is how plants and plant like organisms make sugars.0014

Without those sugars, every single organism that eats will not be able to get energy.0019

Once an animal or single celled organism actually obtains sugars to its diet, where does it go from there?0023

How does it actually extract energy from those sugars?0029

That is what we get into what it is called cellular respiration, the process of breaking down sugars to get that energy.0033

Aerobic respiration is the first kind under this umbrella of cellular respiration.0039

Aerobic respiration is the process of breaking down carbohydrates with the help of oxygen to make ATP.0045

Oxygen (O₂) is the key to making this aerobic respiration.0052

You will see later on that anaerobic respiration is without oxygen.0056

ATP is that energy molecule discussed in previous part of the lesson.0060

Energy molecule meaning it is the kind of energy currency that cells need,0064

to do all the processes that maintain homeostasis and keeps the cell alive.0069

Most of this process occurs in mitochondria.0074

Mitochondria are those powerhouses of the cell.0078

They were discussed in the previous lesson on cells and different organelles, the parts of the cell.0082

Mitochondria, a really efficient site for breaking down sugars and maximizing the output of ATP.0086

They use oxygen as part of the process of maximizing that output.0095

If we will breakdown aerobic respiration to a few different parts,0100

chronologically, it starts out with glycolysis, sugar breakdown.0104

Next is the Krebs cycle, also known as the citric acid cycle, this is the first part that actually takes place inside the mitochondria.0108

Citric Acid cycle is the nickname because citric acid is a molecule that is made in the very beginning of the Krebs cycle.0115

Krebs named after the doctor who first discovered it.0121

Oxidative phosphorylation that is also known as the electron transport chain,0125

but it is more than just electron movement through the mitochondria.0129

It is also movement of protons, as the other half of the process.0133

That is the most important part of the process of aerobic respiration0137

because you get a lot of output of ATP at the end of that.0141

And at the end of the whole process, all these put together,0145

it produces approximately 36 ATP from one glucose molecule, which is pretty good.0148

The reason why there is little approximation symbol is, depending on cellular conditions,0154

you could actually get 38, you could actually get 34, but 36 is typically the most common output0158

that you would get from breaking down 1 glucose molecule with the help of oxygen.0165

Here is an actual micrograph of mitochondria, this is the actual look inside of the cell.0170

You cannot see this close to light microscopes, this is from electron microscopes.0177

Here is a more cartoony looking drawing of a mitochondrion.0181

You could see that there is this inner membrane which you can also see in here, these little folds called cristae.0185

You are going to see that glycolysis actually takes place outside mitochondria.0191

The Krebs cycle takes place in this middle part, notice the matrix, see that word there.0195

And then, oxidative phosphorylation takes place along the cristae.0200

Cristae is all of that folding membrane inside of it, numerous sites for oxidative phosphorylation inside the mitochondria.0205

We focus on glycolysis, the first part of cellular respiration.0216

We can really break up the word into two pieces to better help you understand what it means.0220

It is glycolysis, glyco means sweet or sugar, lysis comes from the lyse, the break down.0229

It really does mean sugar breakdown.0239

If you recall lysosomes, an organelle in cells specializes in breaking down products,0241

whether it is a food molecules, waste products, foreign invaders.0246

Glycolysis literally means breakdown of sugar and it is the breakdown of sugar into pyruvates.0251

Pyruvates, they are half the size of a glucose molecule.0259

Each of those pyruvates is modified to go into the next part, the Krebs cycle.0264

Glycolysis occurs in the cytoplasm, the part of the cell that is outside of the mitochondria.0268

If you recall the cytoplasm is that whole area that is bound by the plasma membrane, but outside of the nucleus.0274

The cytoplasm has a lot of fluid in there, a lot of enzymes, a lot of ions floating around,0282

and of course the majority of the organelles are in there, and that is where glycolysis takes place,0288

then the pyruvates enter the mitochondria.0292

We look at this step by step, you can see that we are starting out with this thing here that got 6 purple dots.0296

This purple kind of magenta looking dots, they actually represent carbon atoms because this is the breakdown of glucose.0304

Glucose is C₆H₁₂O₆ that is the molecular formula for glucose.0311

We are keeping track of the carbon atoms, keep in mind that,0321

attached to each one of these carbons, you would have hydrogen and oxygen.0324

But this just makes it a little simpler looking at glucose, just focusing on the carbons.0328

You could see by the end when we get to these pyruvates, they each have 3 carbons.0332

The first step that has to happen in what they call phase 1 is an energy investment phase.0336

If you want to get energy into breaking apart the sugar molecule, you got to invest some energy.0342

Two ATP's are used, the output once they are used is 2 ADP.0352

If you recall from the previous part of the cellular energy lesson,0359

you have got ATP as that usable energy source, 3 phosphates and ADP 2 phosphate.0362

The third phosphate has come off, where did they go, here they are.0369

π stands for inorganic phosphate, here they are attached to what was glucose.0373

Now, it has a different name, fructose 16 diphosphate, there it is.0378

If you are wondering why do you have to invest this energy?0387

If the whole process here is devoted towards getting energy out of it, why do we have to use energy?0389

You have to invest some energy to get that output at the end.0394

It is a worthwhile investment, it is kind like investing in the stock market but it is better chances here.0397

Investing in a stock market is a risk because you have to buy stock, and the stock value may not go up.0403

When you sell, you might end up with the same amount of money or more like you would like.0408

But in this case, the energy investment is always worth it.0413

Spending this ATP is guaranteed to get you more ATP, by the end.0416

It is a worthwhile investment using those energy molecules.0420

Where do we go from here, now that we have this 6 carbon molecule with the 2 phosphates here?0424

It ends up breaking apart, and keep in mind that the catalyst to all of these steps is an enzyme,0430

as discussed in the previous part in the cellular energy lesson.0436

Enzymes help get these processes going from start to finish.0439

Once they break apart, we have got another step occurring.0444

NAD+, two of them pick up electrons and protons and become NADH.0462

NAD+ that stands for a very long name.0473

NAD is an acronym and it is positively charged, now becomes what is called NADH.0478

What is going on here? Electrons and protons are stripped off of this molecule and they are picked up here.0483

Once electrons and protons bond here to NAD+, you have NADH.0492

It is now an electron carrier, that is kind of its nickname.0496

The electrons and protons that it is carrying, it will dump those off to a later part of the process,0500

further on down the line to help make a lot of ATP.0505

Think of it this way, the formation of two of these NADH,0508

when electrons and protons bond to this is another way of making ATP.0513

Later on, they are going to really contribute to that process of producing that 36 number.0519

Next up, when this split apart, you have a little void for something to bond there.0526

Carbon always likes to make 4 bonds.0534

There is a carbon, there is a carbon, it is bound to its neighboring carbon.0536

This carbon is bound to its neighboring carbon, there is hydrogen and oxygen here0539

but something else can bind there, and guess what does? 2-3 phosphates, inorganic phosphates here.0542

We did not have to use additional ATP for this to happen, they are attached there by an enzyme.0549

Now, we have 1, 2, 3, 4 phosphates that are available on these two molecules.0555

What ends up happening is you get 4 ADP picking up the 1, 2, 3, 4 phosphates to make 4 ATP.0561

Then, that goes away and you finally have 2 pyruvates, 2-3 carbon molecules.0580

If we add up everything we gained at the end, we end up getting as the products.0588

2 pyruvates also known as pyruvic acid, you will see that in certain text books,0598

instead of pyruvates, pyruvic acid, same things just a different way of naming it.0604

2 pyruvates, 2 NADH, and some textbooks will actually write +H + here, signifying the additional proton that it picks up.0609

To simplify things, we are just going to call it NADH.0623

Keep in mind that, it is transporting electrons and protons to the later part of aerobic respiration.0626

The other thing we have is a net gain of 2 ATP.0631

What do we mean by net gain, we actually made 4 ATP here, we used 2.0641

The net gain is, we made 4 ATP but we have to subtract 2 because they went away,0650

they had to be used to make this process occur.0658

That ends up equaling 2 ATP, and that is a net gain.0661

Kind of like with salary, you are living for year, you make a gross salary, the total amount of money you take in.0664

After paying taxes, you get your net salary, after subtracting those taxes that are paid.0671

It is the same idea here, we made 4, have to subtract 2 because the energy investment phase, net gain is 2 ATP.0676

Those are the products you get at the end of glycolysis.0684

The pyruvates enter the next part of the cycle, the Krebs cycle.0687

2 ADH will be used later on, on oxidative phosphorylation.0691

And these 2 ATP, you can use for anything the cell needs at that moment.0695

Now the Krebs cycle, it is also known as the citric acid cycle.0701

Dr. Krebs discovered it, I mistakenly thought when I was a student that it is ‘s, but his name is Kreb.0705

It is actually Krebs, that was his last name.0713

The Krebs cycle, also known as the citric acid cycle, sometimes you will see CA cycle or CAC in textbooks.0717

The pyruvates from glycolysis get modified into something called acetyl-coa, kind of an interesting name here.0725

The acetyl is a 2 carbon molecule that comes from a pyruvate, the coa stands for coenzyme A.0735

I will show you how that happens.0742

It takes 2 pyruvates, Krebs cycle attaches them to a 4 carbon molecule and breaks down to make electron carriers.0745

This is a summary of what happens, when I say it takes 2 pyruvates, they actually have to get modify into this first.0751

Those get attached to the 4 carbon molecule called oxaloacetate or oxo-acyclic acid.0760

I will write it down for you a second.0766

The modification that it has to happen to begin the Krebs cycle is,0768

let us talk about that 3 carbon molecule that we know as pyruvate.0773

Just modeling this after the previous slide, we had those purplish, magenta looking dots, each dot representing a carbon atom.0786

Here they are, here your carbon atoms of pyruvate.0794

What ends up happening is, an enzyme, let me make a little box for it, called coenzyme-A helps modify this to get it in the Krebs cycle.0797

Here is what happens, as CO₂ leaves, one of those red dots, one of those carbons leaves as CO₂.0812

That CO₂ is waste, you know we exhale CO₂ as do animals, and that is a waste product of respiration.0826

You can see that, once that leaves, we are left with just 2 carbons.0835

This is the acetyl that I am telling you about.0844

The other thing that happens is you end up producing a little bit more of that NADH molecule.0850

Just like in glycolysis, this NAD+ picks up electrons and proton becomes NADH0866

and that will be used later on aerobic respiration.0872

Remember, this enzyme attached to there, this enzyme remains there for a bit.0875

That is how you get acetyl-coa, there it is.0884

That is what you need to actually start the Krebs cycle.0889

The acetyl portion combines with that 4 carbon molecule inside the mitochondria matrix,0892

inside that very center part bound by that cristae inside the mitochondria.0898

You will see on a future slide in this lesson an image of the mitochondria, I’m reinforcing that for you.0904

Once coenzyme A gets this to the Krebs cycle, it leaves.0910

This coa will go bye and this acetyl portion will combine with a 4 carbon molecule,0914

like I mentioned earlier called oxaloacetate, oxoacelic acid.0931

That is your 4 carbon molecule combines with the 2 carbon molecule to get 6 carbon molecule known as citric acid.0941

Remember that was the nickname of the Krebs cycle, the citric acid cycle, here it is.0958

Some textbook will call that citrate, same idea with calling this oxoacylic acid or pyruvate, pyruvic acid.0967

Citric acid, we now have officially begun the Krebs cycle, that is formed.0976

The next two steps are actually very similar.0982

Two things happened in each of these first two steps of the Krebs cycle.0989

Once again, carbon dioxide leaves, there is the carbon and carbon dioxide, there is the carbon and carbon dioxide.0994

Citric acid, once CO₂ leaves, 6 - 1 is 5.1001

There are 5 carbons and another one leaves here, like in glycolysis these steps are catalyzed by enzymes.1012

We are down to 4 and do not worry about the names, they all have different names.1023

In the average biology course, those individual names are not stressed.1029

Taking in advanced course like AP Bio or a college level of biochemistry course, you have to know the names.1033

This 4 carbon molecule, notice by the end we still have a 4 carbon molecule.1042

No more CO₂’s will leave after this point because you are generating another 4 carbon molecule, by the end.1048

The CO₂ leaves, what else happens?1058

You will make some more NADH, that is what else happens.1065

More fuel for making ATP, later on in the aerobic respiration process.1083

Those two steps, pretty much the same.1092

Next thing that happens, we end up making ATP.1096

Where is the phosphate come from that ends up been attached to ADP?1103

I will put a little flash of light around it ATP to show you energy.1111

The phosphate gets attached there by virtue of another molecule being broken down.1120

There is actually a GTP molecule that is donating its phosphate to the molecule here,1126

and then that phosphate comes off to make ATP.1133

It is all catalyzed by enzymes, but you end up producing an ATP here which is great, that is more fuel for cellular energy.1138

Still have a 4 carbon molecule of course.1147

Just to save time, I preferred it making those little bonds there but I think you get the picture.1157

A couple more steps remain.1162

Next, we make a new molecule you have not seen yet but I am doing it in green because it does the same thing as NADH.1169

A molecule called FAD picks up some hydrogen in the form of electrons and protons, of course, and it gives FADH2.1179

FAD and NAD+ have the same basic function, they carry electrons and protons to later step1190

after the Krebs cycle to make a lot more ATP.1196

You make one FADH2, one step remains in this magical Krebs cycle.1200

Without it, we would not be able to live.1208

Next up is one more NADH is made.1214

Look at that, it is complete.1230

By the end of this, by the time you have this particular 4 carbon molecule1233

being converted to oxoacetate, you are back to square one, that is the whole point of the cycle.1239

It is a cyclical process where you regenerate what you start with.1245

As long as you keep bringing this acetyl which came from pyruvate, which came from glycolysis,1249

you will continue to do the citric acid cycle within mitochondria.1256

This is happening all the time in the mitochondria.1259

It has to, to keep your cells functioning.1262

It is just something that is millions of times over in cells, in the mitochondria.1266

By the end, what do we have?1272

If we add together all the CO₂ used, including from this intermediate step, total number of CO₂ 1, 2, 3.1275

Total number of NADH is 1,2,3, total number of FADH2 choose one of those and 1 ATP.1290

But, you have to multiply all this by 2 for every glucose,1298

because what do we get from one glycolysis in the previous slide?1302

We got 2 pyruvate, this molecule right here.1306

This is talking about what happens to the 1 pyruvate that is modified and brought into the citric acid cycle.1308

You have to multiply it by 2, in the end, because of Krebs cycle from 1 glycolysis,1319

you get 6 CO₂, you get 1, 2, 3, 4, 8 NADH and 2 FADH2, and 2 ATP.1325

It depends, if you are taking a test, you have to pay attention to the question,1338

if it says from one Krebs cycle, how many NADH do you get? You get 3.1341

But from Krebs cycles that came from 1 glucose, the total number would definitely be more.1347

You have to add up these 3 times 2, and then add up the ones that you got from these particular steps, that is the Krebs cycle.1354

After the Krebs cycle, it leads to oxidative phosphorylation.1366

Oxidative is actually a term that means when a molecule loses electrons.1372

I know the tendency here is to think that it means that it has to do with oxygen.1378

You could remember it that way because oxygen is critical in this particular process.1383

You can see the O₂ right there.1388

But oxidative is the opposite of reductive.1390

A reduction reaction in chemistry or biology means that electrons are added to a molecule.1394

Oxidation or oxidative means the opposite.1403

It is because NADH and FADH2, they are going to give up,1406

they are going to give up those electrons and protons they gain, they will be oxidized.1409

Phosphorylation means attaching the phosphate to something.1414

In this case, we are attaching a phosphate to ADP to make ATP, that was the whole point of aerobic respiration.1418

This is a simplified view of the mitochondrion.1426

If you remember, mitochondria tend to be drawn like this.1430

If I were to make it more 3 dimensional, I would go like this.1440

This is looking inside of a mitochondrion.1446

In here is the matrix, that is where the Krebs cycle takes place.1448

This is known as the cristae, that is what you are seeing here.1452

This is a really simplified cristae, the intramembrane space is in here.1455

It is called intramembrane because it is between the cristae and the outer membrane,1460

which is actually a double membrane on the outside of mitochondria.1465

This part of the drawing is happening here.1471

This region is happening all along here.1474

Just taking this very folded cristae and simplifying it here.1477

Here is where the Krebs cycle happened, that is citric acid cycle.1481

You end up producing NADH and FADH2, and they give up what they gained.1486

They give up electrons and protons.1494

What ends up happening? The electrons go one way, the protons go another way.1496

Let us color code this with red and blue.1501

Let us say that, we are going to use blue for electrons and we are going to use red for protons.1504

From this NADH, protons go here and keep mind that there is a lot of NADH.1518

If you count them all up, there are actually 10 that you get from the breakdown of 1 glucose.1527

Protons will actually go here too.1535

H+ is just another way of thinking about protons, because H meaning-hydrogen,1538

hydrogen atom is a proton with an electron spinning around it.1545

Electrons are negatively charged, protons are positively charge.1549

You take away that negatively charge electron.1556

Protons, positively charged, and you take away the negative, all you have left is these positive.1559

H+ is saying it is a hydrogen atom without an electron which is just a proton.1565

E- is oftentimes what you will see to symbolize electrons.1570

7 But all these H+ or protons building up in the intermembrane space1574

creates just tons of these positive charges, all throughout here.1578

They buildup and build, and they all want to go somewhere, they want to diffuse elsewhere.1582

They end up going through what is called ATP synthase.1588

ATP synthase is a great name for this molecule because it literally means it synthesizes or makes ATP, that is what this is right here.1591

There are tons of these, of all of these membrane proteins found throughout the cristae membrane.1601

All of these H+ build up end going through here, you get a spinning action with ATP synthase.1610

It ends up putting together ADP, adenosine diphosphate with other phosphates, this reaction, to get ATP.1616

You had a lot of ATP in this process.1630

Meanwhile, as that is happening, electrons are being moved through the membrane proteins.1631

Not across the membrane, they are being moved through.1639

These are little electron carriers, you see 1, 3, 4, all these different proteins, they are just moving electrons through.1644

The proteins go across the membrane, electrons go through, and they have a final destination.1656

The electron’s final destination is to meet up with O₂ oxygen gas.1662

This is why oxygen is important for aerobic respiration, that is what makes it aerobic.1669

Oxygen actually takes those electrons, gives them a final destination, they have a place to go,1673

and they end up binding with oxygen along with protons to help make water.1680

Which is actually one of the final products of aerobic respiration, a little bit of water.1685

For most organisms, it is not enough to hydrate them but actually have to drink water, or get it from the food they eat.1691

But there are some organisms out there that actually can get barely enough water from this process to survive,1697

but that is pretty rare.1704

Here is more water being made.1706

The reason why that happens is because O₂ + 4 electrons + 4 protons, 4H+ that give you 2H₂O.1708

That is balanced out for you because you can see that O₂, O times 2,1727

these together actually make 4 hydrogen atoms, 4 electrons + 4 protons H₂ x 2.1735

For every 4 electrons, 4 protons and 1 oxygen gas molecule, you will get 2 water molecules.1741

Of course, you get a lot of ATP, thanks to the movement of electrons and protons.1748

The proton specifically, moving through ATP synthase, helps fuel the production of this.1754

Like we said before, you get a total of 36 ATP from this process.1759

But, from just this alone, ignoring the Krebs cycle, ignoring glycolysis,1765

you will get a number in the lower 30 of the amount of ATP from just oxidative phosphorylation.1772

This is the beauty of how you break down sugars and get energy to fuel your cells.1777

Anaerobic respiration, this would be the cellular respiration without oxygen.1785

Aerobic literally means not air, without air, but specifically means without oxygen, in terms of biology.1799

After glycolysis, glycolysis means by itself is anaerobic,1807

meaning glycolysis happen in cells whether or not oxygen gas is available.1813

When we look at something like a bacterium or yeast that do anaerobic respiration constantly,1819

they do glycolysis just like we do.1826

What happens after that is a little bit different.1829

Glycolysis by itself as anaerobic.1831

After glycolysis, when oxygen is needed to continue with the Krebs cycle and eventually end up at oxidative phosphorylation,1834

If enough O₂ is not available, the pyruvates you got from glycolysis undergo something called fermentation.1841

Fermentation, there are two types and typically an organism does one or the other.1850

Two types of fermentation, they do either lactic acid fermentation which is what we do,1856

animals do in general, and there is alcohol fermentation.1862

Lactic acid fermentation, for example animals do it.1866

Alcohol fermentation, yeast, like I said you know bacteria will do too.1875

Animals produce lactic acid, especially in their muscles.1884

When your muscles are working really hard, and maybe a lot of energy to do what you are asking to do.1887

If not enough O₂ is gone to the muscle for what you are asking it to do,1893

you get a burning sensation, and that is thanks to the buildup of lactic acid.1897

It eventually goes away, you end up breathing in more oxygen.1902

Lactic acid can be converted back into pyruvate, takes it to the processes in your liver.1905

Alcohol fermentation is another form of fermentation, and yeast do it.1910

That is how we end up being able to make beer, wine, and liquor.1914

They are able to make bread, lots of other foods, thanks to fermentation.1919

The release of CO₂ from fermentation will make the bread rise in the oven.1924

The thing with aerobic respiration from this as a whole, the only ATP you get is what you got from glycolysis.1930

After glycolysis do fermentation, there is no production of ATP.1938

In terms of efficiency of breaking down sugars to get a lot of ATP out of it, not nearly as good as aerobic respiration.1942

How these processes occur, well lactic acid fermentation, I will draw it here in black.1951

If we have those pyruvates with 3 carbons, an enzyme helps modify it1963

into what is known as lactic acid, to make this fermentation happen.1977

No CO₂ leaves because lactic acid has the same number of carbon atoms 1, 2, 3 as pyruvate.1985

I should actually make this singular because it is 1 pyruvate, but it does happen to each one of them.1993

A pyruvate is modified into a lactic acid.1999

What needs to happen is, NADH gives back what it gained and converts back to NAD+.2003

It gives back electrons and protons it gained to the process of making pyruvate to turn it into lactic acid.2014

Research has shown that the building of lactic acid in the human body, specifically the muscles, encourages you to inhale more oxygen.2021

It is a nice mechanism to get a lot more oxygen in your system,2031

so you can stop doing lactic acid fermentation and get back to aerobic respiration which can give you a lot more ATP.2034

Now, I’m going to show you alcohol fermentation in blue.2043

Here is how alcohol fermentation is a little bit different.2049

We still have these 3 carbon pyruvate, there is a major difference though.2052

A carbon leaves, there is a carbon leaving there via CO₂,2065

and we end up with the 2 carbon molecule known as ethanol or ethyl alcohol, same thing.2069

Ethanol, the alcohol that is in liquor, wine, and beer,2076

that is what you get from alcohol fermentation that is why it is called that.2082

Just like in lactic acid fermentation, NADH gives back what it gained and AD+ forms.2087

It gives back those electrons and protons to help turn pyruvate in ethanol.2102

The CO₂ release that what makes bread rise.2106

The CO₂ release also explains bubbles in champagne, in beer, sparkling wine.2109

Oftentimes, breweries will let the natural carbonation just go to vapor and leave the liquid,2117

and they will put back a specific amount of carbon dioxide back in.2128

Traditionally, the bubbles that were there when your alcohol was first made, is from this process,2132

from this natural process of alcohol fermentation.2139

It comes from glycolysis, that is how you got pyruvate.2143

It is just from not having that O₂, that is the main difference with anaerobic respiration.2147

You can think of it this way, glycolysis and then there is a fork in the road.2153

When there is O₂, you get Krebs and oxidative phosphorylation.2162

When you have no O₂ available, you get fermentation.2172

This kind of a fork in the road, glycolysis is what aerobic and anaerobic respiration have in common.2180

Definitely, anaerobic respiration is something that is done by yeast and certain kinds of bacteria,2186

and done on your muscles, particular times when we are really exhausted.2192

Not as efficient, not as beneficial as something like aerobic respiration, it gives you a lot more ATP.2196

When we compare aerobic respiration versus photosynthesis, I wanted to show you some interesting things here.2204

Let us do aerobic respiration in purple.2211

And of course, we will do photosynthesis in green.2242

At first glance, there is a certain kind of perimysium here.2270

You can see that the reactants of one are the products of the other, and vice versa.2276

The only difference is what kind of energy we are talking about.2281

The output of energy from the breakdown of sugars to aerobic respiration, that energy ends up being encapsulated in ATP.2285

All that energy release from the breakdown of this, gives you those approximate 36 ATP.2293

Conversely, the energy that is required to make this process build sugar is from the sun.2299

This is not saying, we have to breakdown ADP.2307

No, this is particular energy here, this is from sunlight, of course, solar energy, used to make the product of glucose.2310

Oxygen, waste product for photosynthesis, but plants will use oxygen.2319

Plants, oftentimes do aerobic respiration with their mitochondria, once they have built a sugar like glucose,2323

they will break it down to get ATP to keep their cells going.2331

This process up on top, aerobic respiration in general, exergonic, release of energy.2334

This endergonic, storing of energy, input of energy that has to happen to build a sugar.2347

These processes constantly fuel each other because think about it, if this process makes glucose,2360

releases oxygen, that is how you get this process being possible.2368

Animals and other organisms that eats, that have to consume, if you are a heterotrophy,2374

the taking in of energy source, they need glucose, they need oxygen to breakdown efficiently.2379

What they end up producing helps to fuel this, they really do keep it going around.2385

Other things that they have in common, not necessarily difference is electron transport.2394

Both of them have an electron transport chain, both of them have ATP synthase,2399

both of them have proteins that transport electrons, that transport protons, and help make ATP as part of the process.2404

One of them has ATP being made, as kind of the end of it.2415

One of them has ADP being made in the beginning.2419

If you think about the timing of electron transport in photosynthesis and aerobic respiration,2422

in terms the sequence, it happens very early on in the light reactions of photosynthesis.2427

It happens towards the end of aerobic respiration,2432

that just lends itself to this reversal of how things are happening with these processes.2434

It is amazing to look at them and compare them, and think about how they fuel each other2441

for billions of years, they will continue to do so.2446

Thank you for watching