Cellular Respiration (UPDATED)

Summary

This educational video script delves into the process of aerobic cellular respiration in eukaryotic cells, focusing on how cells generate ATP, the energy currency vital for life. It outlines the steps of glycolysis, the Krebs Cycle, and the electron transport chain, highlighting the role of mitochondria and the importance of oxygen. The script also touches on the efficiency of ATP production and the potential for fermentation in anaerobic conditions. It concludes with the significance of understanding these processes for treating mitochondrial diseases, encouraging viewers to stay curious about cellular functions.

Takeaways

• 🌞 Morning people and non-morning people have different energy levels upon waking up, with some needing more time and coffee to energize.
• 💫 Cells, unlike humans, do not have the luxury of time to regain energy and must constantly perform processes to survive, requiring ATP.
• 🔋 ATP, or adenosine triphosphate, is a nucleic acid with three phosphates and serves as the energy currency for cells.
• 🔬 Both prokaryotic and eukaryotic cells need to produce ATP, but the methods can vary, with eukaryotic cells focusing on aerobic cellular respiration.
• 🌿 Eukaryotic cells, found in organisms like protists, fungi, animals, and plants, have membrane-bound organelles, including mitochondria, which play a crucial role in ATP production.
• 🔄 Aerobic cellular respiration involves converting glucose into ATP and consists of glycolysis, the Krebs cycle, and the electron transport chain.
• 🚀 Glycolysis is the first step, occurring in the cytoplasm without oxygen, converting glucose into pyruvate, yielding 2 ATP and 2 NADH.
• 🌀 The Krebs cycle, or Citric Acid Cycle, is an aerobic process in the mitochondrial matrix that produces 2 ATP, 6 NADH, and 2 FADH2, along with carbon dioxide.
• ⚡ The electron transport chain and chemiosmosis require oxygen and generate a proton gradient, allowing ATP synthase to produce ATP from ADP and inorganic phosphate.
• 💧 Oxygen acts as the final electron acceptor, combining with hydrogen to form water, which is a product of the cellular respiration process.
• 🔢 The total ATP yield from cellular respiration can vary, with estimates ranging from 30-38 ATP molecules per glucose molecule, depending on factors like the proton gradient.

Q & A

What is ATP and why is it important for cells?

ATP stands for adenosine triphosphate, a type of nucleic acid packed with three phosphates. It serves as the energy currency for cells, providing the necessary energy for various cellular processes, regardless of whether the cell is a prokaryote or a eukaryote.

How does the process of ATP production differ between prokaryotic and eukaryotic cells?

Both types of cells need to produce ATP, but the process can differ. Eukaryotic cells, which have membrane-bound organelles like mitochondria, carry out aerobic cellular respiration, which includes glycolysis, the Krebs cycle, and the electron transport chain. Prokaryotic cells, lacking membrane-bound organelles, may use different mechanisms.

What are the key organelles involved in aerobic cellular respiration in eukaryotic cells?

In eukaryotic cells, the mitochondria play a crucial role in aerobic cellular respiration, particularly in the Krebs cycle and the electron transport chain. The cytoplasm is also involved, especially during glycolysis.

What is the role of glucose in cellular respiration?

Glucose serves as the primary reactant in cellular respiration. It is broken down to produce ATP, which is used by cells for energy. Non-photosynthetic organisms, such as humans and amoebas, must obtain glucose from their food sources.

Can you explain the process of Glycolysis?

Glycolysis is the first step of cellular respiration that occurs in the cytoplasm and does not require oxygen. During glycolysis, one glucose molecule is converted into two pyruvate molecules, yielding a net gain of 2 ATP and 2 NADH molecules.

What happens to the pyruvate produced in glycolysis?

The pyruvate produced in glycolysis is transported into the mitochondria via active transport, where it is oxidized and converted into acetyl CoA, releasing carbon dioxide and producing 2 NADH molecules.

What is the Krebs cycle, and what are its products?

The Krebs cycle, also known as the Citric Acid Cycle, is the second step of aerobic cellular respiration that occurs in the mitochondrial matrix. It produces carbon dioxide, 2 ATP, 6 NADH, and 2 FADH2.

Can you describe the electron transport chain and chemiosmosis?

The electron transport chain and chemiosmosis are the third steps in aerobic cellular respiration, occurring in the inner mitochondrial membrane. They require oxygen and involve the transfer of electrons from NADH and FADH2 to protein complexes and electron carriers, generating a proton gradient that powers ATP synthase to produce ATP.

What is the significance of the ATP synthase enzyme?

ATP synthase is a crucial enzyme that catalyzes the conversion of ADP to ATP by adding a third phosphate. It harnesses the energy from the proton gradient created by the electron transport chain to synthesize ATP, the cell's energy currency.

How does the process of fermentation differ from aerobic cellular respiration?

Fermentation is an alternative process that some cells can use to produce ATP in the absence of oxygen. It is less efficient than aerobic cellular respiration and does not involve the Krebs cycle or the electron transport chain.

What is the significance of the number of ATP molecules produced per glucose molecule in cellular respiration?

The number of ATP molecules produced per glucose molecule, which can range from 30-38, indicates the efficiency of the cellular respiration process. However, it's important to note that this number can vary based on several factors, such as the proton gradient, and should be considered as a range rather than a fixed value.

Why is research on mitochondrial diseases important?

Mitochondrial diseases are important to study because mitochondria play a central role in ATP production. Understanding these diseases can lead to improved treatments and potentially save lives, given the critical role that ATP plays in cellular function and survival.

Outlines

00:00

🌞 Morning Energy and ATP Production

The video introduces the concept of ATP as the energy currency for cells, comparing the morning sluggishness of humans to the constant energy production in cells. It explains that all cells, whether prokaryotic or eukaryotic, must produce ATP through processes like aerobic cellular respiration. The video focuses on eukaryotic cells, which include those found in protists, fungi, animals, and plants, and highlights the role of mitochondria in aerobic cellular respiration. The equation for aerobic cellular respiration is presented, showing the conversion of glucose and oxygen into carbon dioxide, water, and ATP. The video also touches on the reliance of germinating bean seeds on stored glucose and cellular respiration for growth before they can perform photosynthesis.

05:00

🔋 Steps of Aerobic Cellular Respiration and ATP Yield

This paragraph delves into the three main steps of aerobic cellular respiration in eukaryotic cells: Glycolysis, the Krebs Cycle (Citric Acid Cycle), and the Electron Transport Chain with chemiosmosis. Glycolysis, an anaerobic process occurring in the cytoplasm, converts glucose into pyruvate, yielding a net of 2 ATP and 2 NADH molecules. Pyruvate is then transported into the mitochondria and oxidized to acetyl CoA, releasing carbon dioxide and producing more NADH. The Krebs Cycle, an aerobic process in the mitochondrial matrix, generates 2 ATP, 6 NADH, and 2 FADH2, along with carbon dioxide. The Electron Transport Chain and chemiosmosis, requiring oxygen and occurring at the inner mitochondrial membrane, use the electrons from NADH and FADH2 to create a proton gradient, ultimately producing a variable amount of ATP, with estimates ranging from 26-34 ATP molecules per glucose molecule. The paragraph concludes by emphasizing the importance of ATP production for cellular functions and the deadly effects of substances like cyanide that can block this process.

Keywords

💡ATP

ATP, or adenosine triphosphate, is a nucleic acid that serves as the primary energy currency for cells. It is crucial for cellular processes as it provides the energy needed for various functions. In the video, it is highlighted that all cells, regardless of their type, must produce ATP to survive. The production of ATP is the central theme of the video, with the process of aerobic cellular respiration being described as a way to generate ATP in eukaryotic cells.

💡Eukaryotic Cells

Eukaryotic cells are cells that contain membrane-bound organelles, such as a nucleus and mitochondria. They are found in protists, fungi, animals, and plants. The video emphasizes the role of eukaryotic cells in aerobic cellular respiration, particularly how mitochondria within these cells are vital for the production of ATP through the process of cellular respiration.

💡Aerobic Cellular Respiration

Aerobic cellular respiration is the process by which cells generate ATP in the presence of oxygen. The video focuses on this process in eukaryotic cells, explaining how it involves several steps, including glycolysis, the Krebs Cycle, and the electron transport chain. This process is essential for cells to produce the energy they need to function.

💡Glycolysis

Glycolysis is the first step of cellular respiration and occurs in the cytoplasm of the cell. It is an anaerobic process, meaning it does not require oxygen. During glycolysis, glucose is converted into pyruvate, yielding a net gain of 2 ATP molecules and 2 NADH. The video explains that glycolysis is a critical step in preparing glucose for further processing in the ATP production pathway.

💡Mitochondria

Mitochondria are organelles found in most eukaryotic cells and play a significant role in the production of ATP. They are the site of the Krebs Cycle and the electron transport chain, which are essential steps in aerobic cellular respiration. The video highlights the importance of mitochondria as the 'powerhouses' of the cell, where some of the ATP production processes take place.

💡Krebs Cycle

The Krebs Cycle, also known as the Citric Acid Cycle, is the second step in aerobic cellular respiration. It occurs in the mitochondrial matrix and is an aerobic process that requires oxygen. The cycle involves the conversion of acetyl CoA into carbon dioxide, ATP, NADH, and FADH2. The video explains that this cycle is intricate and essential for the production of ATP.

💡Electron Transport Chain

The electron transport chain is a complex process that takes place in the inner mitochondrial membrane of eukaryotic cells. It is a critical step in aerobic cellular respiration, requiring oxygen. The chain involves the transfer of electrons from NADH and FADH2 to protein complexes, generating a proton gradient that powers the production of ATP. The video describes this process as a beautiful mechanism for ATP synthesis.

💡Chemiosmosis

Chemiosmosis is the process by which a proton gradient across a membrane is used to produce ATP. In the context of the video, chemiosmosis occurs during the electron transport chain, where protons flow through ATP synthase, an enzyme that adds a phosphate to ADP to create ATP. This process is central to the production of ATP in cellular respiration.

💡NADH and FADH2

NADH and FADH2 are coenzymes involved in the transfer of electrons during the electron transport chain. They are produced during glycolysis and the Krebs Cycle, respectively, and are essential for the production of ATP. The video explains that these coenzymes carry electrons to the electron transport chain, which is a crucial step in generating the energy needed for ATP synthesis.

💡Fermentation

Fermentation is an alternative process to aerobic cellular respiration that occurs when oxygen is not available. It is less efficient but allows cells, such as certain bacteria and yeast, to produce ATP in anaerobic conditions. The video mentions fermentation as a way that cells can still generate ATP when oxygen is scarce.

💡Mitochondrial Diseases

Mitochondrial diseases are disorders that affect the mitochondria, which can impair the cell's ability to produce ATP. The video points out the importance of mitochondria in ATP production and the need for increased research on diseases that affect these organelles. Understanding and treating mitochondrial diseases is highlighted as a critical area of study.

Highlights

Cells require ATP for energy and perform various processes to maintain it.

ATP stands for adenosine triphosphate, a nucleic acid with three phosphates.

All cells, whether prokaryotic or eukaryotic, need to produce ATP.

Aerobic cellular respiration is a method used by many organisms to make ATP, with a focus on eukaryotic cells in this video.

Eukaryotic cells contain organelles like the nucleus and mitochondria, with mitochondria playing a key role in aerobic respiration.

The overall equation for aerobic cellular respiration is presented, showing similarities to photosynthesis.

Glucose is a product of photosynthesis but a reactant in cellular respiration.

Germinating bean seeds rely on cellular respiration to break down stored glucose for ATP production.

Plants can perform both photosynthesis and cellular respiration, while humans and amoebas need external glucose sources.

Glycolysis is the first step of cellular respiration, converting glucose into pyruvate without oxygen.

Glycolysis yields 2 pyruvate, 2 ATP, and 2 NADH molecules.

Pyruvate is transported into mitochondria and oxidized to acetyl CoA, releasing carbon dioxide and producing NADH.

The Krebs Cycle, or Citric Acid Cycle, is an aerobic process within the mitochondrial matrix.

The Krebs Cycle generates 2 ATP, 6 NADH, and 2 FADH2, along with releasing carbon dioxide.

The electron transport chain and chemiosmosis involve the inner mitochondrial membrane and require oxygen.

Electrons from NADH and FADH2 are transferred to create a proton gradient, which powers ATP synthase to make ATP.

Oxygen combines with hydrogen to form water, the final electron acceptor in the electron transport chain.

The number of ATP molecules produced per glucose can vary, with estimates ranging from 26-34 in the electron transport chain alone.

Including glycolysis and the Krebs Cycle, the total ATP yield per glucose molecule ranges from 30-38.

Fermentation is an alternative process for ATP production in the absence of oxygen.

Cyanide can block ATP production, highlighting the critical role of ATP in cellular processes.

Increased research on mitochondrial diseases is crucial due to the importance of mitochondria in ATP production.

Transcripts

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Are you a morning person?

One of us is and one of us is definitely not.

Mainly because, when I wake up in the morning, it just takes a while for me to get my energy

back.

It takes a lot of time- and coffee -for that to happen for me.

Cells really don’t have that luxury.

They are busy performing cell processes all the time: active transport of many substances

needed for their survival, for example.

And the energy currency they need, specifically, is ATP.

ATP stands for adenosine triphosphate.

It’s a type of nucleic acid actually, and it is action packed with three phosphates.

We have a video all about ATP and how it works as an energy currency.

So where am I going with this?

Well, cells have to make this ATP.

It doesn’t really matter what kind of cell you are - prokaryote or eukaryote - you have

to make ATP.

The process for making that ATP can be different, however, depending on that type of cell.

One way is called aerobic cellular respiration.

Lots of organisms can do aerobic cellular respiration, but this video is specifically

going to go into aerobic cellular respiration in eukaryotic cells.

That means, this video is talking about the process within cells that have membrane-bound

organelles such as a nucleus and mitochondria.

Eukaryotic cells include the cells you’d find in protists, fungi, animals, and plants.

The mitochondria- which can be found in most eukaryotic cells - are going to be kind of

a big deal in this aerobic cellular respiration, because some of the process occurs in the

mitochondria.

So let’s get started.

Remember the major goal for any organism performing this: it’s to make ATP.

Ok, here’s the overall look at the equation for aerobic cellular respiration.

Remember that reactants (inputs) are on the left side of the arrow.

And products (outputs) are on the right side of the arrow.

This equation, by the way, looks remarkably similar to photosynthesis.

Look at how the reactants and products are on different sides.

While that doesn’t mean they’re simply opposites, it does show that they have substances

in common.

In photosynthesis, organisms make glucose.

Notice how glucose is a product.

But in cellular respiration, organisms break the glucose down to make ATP.

Fun fact: You know how when a bean seed first germinates in the ground, it isn’t able

to do photosynthesis yet?

Yeah, the germinating bean is relying on glucose that it has stored and it’s doing cellular

respiration to break it down to make ATP so it can grow.

Of course, once it starts to mature and develop leaves, it can do photosynthesis.

It will be able to do both photosynthesis and cellular respiration.

Plants make glucose in photosynthesis and they break it down in cellular respiration:

they can do both.

But if you aren’t photosynthetic, such as a human or an amoeba, you have to find a food

source to get your glucose.

You need glucose to get this process started, and we’re going to assume that we’re starting

with one glucose molecule.

Step #1 Glycolysis.

This step takes place in the cytoplasm, and this step does not require oxygen.

It’s considered anaerobic.

In glycolysis, glucose, the sugar from the equation, is converted into a more usable

form called pyruvate.

Glycolysis usually takes a little ATP itself to start up.

The net yield from this step is approximately 2 pyruvate and 2 ATP molecules.

And 2 NADH.

What is NADH?

NADH is a coenzyme, and it has the ability to transfer electrons, which will be very

useful in making even more ATP later on.

We’ll get to that in a minute.

Now, an intermediate step occurs.

The 2 pyruvate are transported by active transport into the mitochondria, specifically the mitochondrial

matrix.

In the mitochondria, pyruvate is oxidized.

The 2 pyruvate are converted to 2 acetyl CoA, which will be used by the next step.

Carbon dioxide is released, and 2 NADH are produced.

Step #2 The Krebs Cycle - also called the Citric Acid Cycle.

Still in the mitochondrial matrix.

The Citric Acid Cycle is considered an aerobic process.

While the cycle doesn’t directly consume oxygen, some of the events in the cycle need

oxygen to continue.

To learn more about this intricate cycle where the 2 acetyl CoA will enter, check out the

further reading suggestions in the video details.

Carbon dioxide is released.

We also produce 2 ATP, 6 NADH, and 2 FADH2.

FADH2 is also a coenzyme, like NADH, and it will also assist in transferring electrons

to make even more ATP.

Step #3 The electron transport chain and chemiosmosis.

This is, just, a beautiful thing, really.

In eukaryotic cells, this is still in the mitochondria, and to be more specific, it’s

involving the inner mitochondrial membrane.

We do require oxygen for this aerobic step.

This is a very complex process, and we are greatly simplifying it by saying that electrons

are transferred from the NADH and FADH2 to protein complexes and electron carriers.

The electrons are used to generate a proton gradient as protons are pumped across to the

intermembrane space.

All these protons being pumped out into this intermembrane space generates an electrical

and chemical gradient.

The thing is, if you remember from our cell transport video, ions (like the H+) don’t

easily travel across membranes directly without something to travel through.

The protons can travel through an amazing enzyme called ATP synthase.

If I could be any enzyme, I’d be ATP synthase, because it has the ability to make ATP by

adding a phosphate to ADP.

ADP is a precursor to ATP.

ADP has two phosphates, but if it obtains a third phosphate, it becomes ATP.

So, in chemiosmosis, the protons travel down their electrochemical gradient through a portion

of the ATP synthase, powering it to make ATP.

The ultimate goal.

Oxygen is the final acceptor of the electrons.

When oxygen combines with two hydrogens, you get H20 - water.

If you remember from our equation, water is a listed product.

Now, the electron transport chain and chemiosmosis step makes a lot more ATP compared to the

other two previous steps.

How much?

So, I’ve noticed in my years of teaching and the assortment of textbooks I’ve collected

over the years, there are some different numbers in cellular respiration charts.

In fact, you can even see them change a bit in different editions of the same book.

And it’s made me want to emphasize that it’s important to not just memorize a number,

because it really is more of a range.

I want to focus less on that number of ATP made per glucose molecule because it depends

on a lot of variables.

One variable is the gradient we were talking about: how many protons were pumped across

that mitochondrial membrane.

You can see more variables discussed in the factual references, and those references have

estimates ranging from 26-34 molecules of ATP per glucose molecule in the electron transport

chain and chemiosmosis step alone.

Then if you add the other two steps: Krebs – otherwise known as the Citric Acid Cycle

- and glycolysis, you could estimate a range of anywhere between 30-38 net ATP molecules

total per molecule of glucose.

Again, to emphasize, a range.

Now, this was just one way of creating ATP.

But like we had said at the beginning, all cells have to make ATP, but the way that they

do it can differ.

If there's no oxygen available, some cells have the ability to perform a process known

as fermentation.

It’s not as efficient, but it can still make ATP when there isn’t oxygen.

We have a video about that!

We can’t emphasize enough how important the process of making ATP is for cells.

For example, cyanide - which is found in some rat poisons - can block a step in the electron

transport chain, which would block ATP production.

A poison that prevents ATP from being produced can be deadly.

With the important role that mitochondria have in ATP production, there is also a demand

for increased research on mitochondrial diseases.

We are confident that the understanding of how to treat these diseases will continue

to improve as more people, like you, ask questions.

Well, that’s it for the Amoeba Sisters, and we remind you to stay curious.