Introduction to Aerobic Cellular Respiration - Online Tutor, Practice Problems & Exam Prep

Aerobic cellular respiration is a multi-stage process that converts glucose and oxygen into carbon dioxide, water, and ATP, the energy currency of cells. This redox reaction involves the oxidation of glucose and the reduction of oxygen, with oxygen acting as the final electron acceptor. The four main stages include glycolysis, pyruvate oxidation, the Krebs cycle, and the electron transport chain, primarily occurring in mitochondria for eukaryotes. Understanding these stages is crucial for grasping cellular metabolism and energy production.

Introduction to Aerobic Cellular Respiration

In this video, we're going to begin our introduction to aerobic cellular respiration. Aerobic cellular respiration, as its name implies, is the aerobic process of breaking down the sugar glucose, which acts as food for the cell, in order to make lots of energy for the cell in the form of ATP. Now, "aerobic" is a term that refers to the requirement of the presence of oxygen gas, and the chemical formula for oxygen gas is O2. Moving forward in our course, we're mainly going to focus on aerobic cellular respiration, or cellular respiration in the presence of oxygen gas. However, in some of our videos much later in our course, we'll also discuss what happens with cellular respiration under anaerobic conditions when there is no oxygen present. But for now, we're going to focus on aerobic cellular respiration. Aerobic cellular respiration actually occurs in multiple different stages that we'll discuss more as we move forward in our course. Most of these stages of aerobic cellular respiration occur inside the organelle called the mitochondria in eukaryotic cells. Recall that only eukaryotic cells contain mitochondria, and prokaryotic cells do not contain those membrane-bound organelles like mitochondria. Most of the stages of cellular respiration occur in mitochondria in eukaryotes. But there is one stage, specifically glycolysis, that we'll discuss more later in our course, that occurs just outside the mitochondria. Other than that, all the other stages occur in the mitochondria in eukaryotes. Now, in prokaryotes, on the other hand, they again lack mitochondria. They are still able to perform aerobic cellular respiration; it's just that the location of the stages of aerobic cellular respiration is going to be different. Because prokaryotes lack mitochondria, most of the cellular respiration stages are going to occur in the cytoplasm of the prokaryotic cells. We'll talk more about these stages of aerobic cellular respiration as we move forward in our course. As we progress, we're mainly going to focus on aerobic cellular respiration in eukaryotes. You'll frequently see us showing the mitochondria. Whenever you see the mitochondria, you can assume that this process is occurring in eukaryotic organisms. We'll discuss a little about cellular respiration in prokaryotes and will specifically mention the most important features that you should know about cellular respiration in prokaryotes as we move forward. But for now, let's take a look at this image down below here, which is showing you the overall chemical equation for aerobic cellular respiration, an important equation for you to be familiar with. Notice that we're showing you aerobic cellular respiration occurring mainly inside the mitochondria in eukaryotic organisms. The chemical equation for aerobic cellular respiration begins with glucose and oxygen gas as reactants. These reactants undergo many different stages of cellular respiration, represented by a single arrow, and, ultimately, glucose and oxygen gas are converted into carbon dioxide, water, and ATP, a form of energy for the cell. The main purpose of cellular respiration is for the cell to obtain this energy because it can use this ATP to drive many other cellular processes. This is just our introduction to aerobic cellular respiration, and we'll be able to talk a lot more about this process as we move forward in our course. I'll see you all in our next video.

Aerobic Cellular Respiration is a Redox Reaction

In this video, we're going to talk about how aerobic cellular respiration is a redox reaction. And, once again, the overall chemical equation for aerobic cellular respiration is a redox reaction. Recall from our previous lesson videos that this just means that it involves the transfer of electrons between molecules. Furthermore, remember that the way we can remember redox reactions is by remembering LEO, "the lion goes grrr". Substances that lose electrons are oxidized, whereas substances that gain electrons are reduced. By the end of the process, glucose is going to lose electrons, which means that glucose is going to be oxidized. On the other hand, oxygen gas is going to gain electrons, and so oxygen gas is going to be reduced. Later in our course, we will learn that oxygen is the final electron acceptor, meaning it's the last thing that accepts or gains the electrons. This goes hand in hand with oxygen being reduced.

Let's take a look at the chemical equation for aerobic cellular respiration. Notice over here on the left-hand side, we're showing you the chemical structure for glucose. You all should know that glucose's chemical formula is C6H12O6. Aerobic cellular respiration will take glucose, as well as six molecules of oxygen gas, and convert the glucose and the six molecules of oxygen gas into six molecules of carbon dioxide gas, six molecules of water, and a substantial amount of ATP, somewhere between 30 to 38 ATP. Making a significant amount of ATP is really the main point of aerobic cellular respiration.

It breaks down foods such as sugars like the monosaccharide glucose using oxygen, and when it breaks down that glucose, those foods, it is able to form large amounts of ATP. It also produces carbon dioxide and water as a byproduct. During this process, the glucose molecule is going to lose electrons, meaning it is oxidized, and all those electrons are going to be used to generate ATP. Moreover, the oxygen gas molecule is going to gain electrons. We will learn later in our course that oxygen is the final electron acceptor that gains the electrons. As it gains the electrons, oxygen gas is reduced and ultimately converted into water.

This chemical reaction should be very familiar to you and recognizable for your exam, as professors tend to want their students to be very familiar with the overall chemical equation for aerobic cellular respiration. This concludes our introduction to how aerobic cellular respiration is a redox reaction, and we will be able to get some practice applying these concepts as we move forward in our course. We will continue to learn more about aerobic cellular respiration as well. I'll see you all in our next video.

Which one of the following molecules is a by-product of cellular respiration?

a) Water.

b) Glucose.

c) Pyruvate.

d) Oxygen.

e) ADP.

• A. Water.
• B. Glucose.
• C. Pyruvate.
• D. Oxygen.
• E. ADP.

Which of the summary statements below describes the results of the following reaction?

C₆H₁₂O₆ + 6 O₂ → 6 CO₂ + 6 H₂O + Energy

a) C₆H₁₂O₆ is oxidized and O₂ is reduced.

b) O₂ is oxidized and H₂O is reduced.

c) CO₂ is reduced and O₂ is oxidized.

d) O₂ is reduced and CO₂ is oxidized.

• A. C₆H₁₂O₆ is oxidized and O₂ is reduced.
• B. O₂ is oxidized and H₂O is reduced.
• C. CO₂ is reduced and O₂ is oxidized.
• D. O₂ is reduced and CO₂ is oxidized.

Stages of Aerobic Cellular Respiration

This video we're going to introduce the stages of aerobic cellular respiration. And so aerobic cellular respiration actually includes 4 metabolic pathways or reactions that we are referring to as stages. And so notice down below on the left-hand side we're showing you the aerobic cellular respiration stages specifically in eukaryotes or in eukaryotic organisms. And on the right-hand side, we're showing you the stages of aerobic cellular respiration in prokaryotes. And what you'll notice is that the stages are pretty much identical for the most part. They are going to be very similar. And so, each of the stages are going to be glycolysis followed by pyruvate oxidation, followed by the Krebs cycle or the citric acid cycle. Those are, Krebs cycle and citric acid cycle are referring to the same exact pathway. And then the electron transport chain and chemiosmosis. And notice that we have the same exact stages over here in prokaryotes. Now, what is different, is the location of the stages between eukaryotes and prokaryotes. And so notice that in eukaryotic organisms, the vast majority of cellular respiration occurs in the mitochondria. And the mitochondria is represented by this orange structure that you see in the background. The only stage that does not occur in the mitochondria in eukaryotes is glycolysis, the very first stage of aerobic cellular respiration. And glycolysis occurs in the cytoplasm for eukaryotes. But for prokaryotes over here, notice that pretty much all of cellular respiration occurs in the cytoplasm of the prokaryotes. And that's because again prokaryotes do not have mitochondria. Now do notice that in the electron transport chain and chemiosmosis, this is going to be found specifically And And so this here concludes our brief introduction to the 4 stages of aerobic cellular respiration, glycolysis, pyruvate oxidation, Krebs cycle or citric acid cycle, and electron transport chain and chemiosmosis. And as we move forward in our course, we're going to look at each of these 4 stages in a lot more detail. So I'll see you all as we move forward.

Remembering Stages of Aerobic Cellular Respiration

In this video, I'm going to share with you a silly way to help you remember the stages of aerobic cellular respiration, which you might recall from our previous lesson videos, is glycolysis, pyruvate oxidation, the Krebs Cycle, and the electron transport chain. All you need to do to remember the aerobic cellular respiration stages in the correct order is that giant pandas killed Einstein. Notice, down below, we're showing you here a giant panda that is attacking and killing Einstein right here. If you can remember "Giant Pandas Killed Einstein," then hopefully that can help you to remember the four stages of aerobic cellular respiration in the correct order, which are once again glycolysis, pyruvate oxidation, the Krebs cycle, and the electron transport chain. The first letter here of these words all match up. Again, it's just a silly way to help you remember these stages. That being said, this here concludes this video, and I'll see you all in our next one.

Introduction to Aerobic Cellular Respiration Example 1

So here we have an example problem that's asking which of the following options list the stages of aerobic cellular respiration in the correct order. And we've got these 4 potential answer options down below. And so, of course, we know from our last lesson video that when it comes to remembering the stages of aerobic cellular respiration in the correct order, really all we need to remember is that "Giant Pandas Killed Elvis". And by remembering "Giant Pandas Killed Elvis", we'll be able to remember the stages in the correct order. And so, recall that the "Giant Pandas Killing Elvis" stands for the "GPKE" here, and the "Giant" stands for glycolysis, the "P" stands for pyruvate oxidation, the "K" here stands for Krebs Cycle, and the "E" here stands for electron transport chain chemiosmosis. And so it needs to be these stages in this particular order. And the only answer option that matches this particular order from our mnemonic is option B, glycolysis, followed by pyruvate oxidation followed by Krebs cycle, and then finally the electron transport chain in chemiosmosis. And so, option B here is going to be the correct answer for this example problem. And that concludes this example, so I'll see you all in our next video.

Map of the Lesson on Cellular Respiration

In this video, we're going to introduce our map of the lesson on cellular respiration, which is this image that you see down below. And so this image is a map or an outline of our lesson moving forward. And so you can refer to this image as we move forward in our course and continue to talk more about cellular respiration. Notice towards the top of our map here, we have cellular respiration. And moving forward in our course, we're mainly going to be talking about cellular respiration in the presence of oxygen or where oxygen is available. In other words, we're going to talk mostly about aerobic respiration, which is cellular respiration in the presence of oxygen with oxygen present. Now later in our course we will talk a little bit about cellular respiration in the absence of oxygen without oxygen. And we'll mainly talk about anaerobic respiration as well as fermentation. Now, when oxygen is present, oxygen is going to serve as what is known as the final electron acceptor and we'll get to talk more about that as we move forward in our course.

Recall that one of the main purposes of cellular respiration is to generate energy in the form phosphorylation, or it could be generated via oxidative phosphorylation. We'll discuss the differences between substrate level phosphorylation and oxidative phosphorylation as we move forward in our course. Notice that the first and the third stages of cellular respiration are going to generate ATP via substrate level phosphorylation. The second stage, which is pyruvate oxidation, it turns out that it does not generate ATP directly. And then notice that the fourth stage of aerobic cellular respiration is going to generate ATP via oxidative phosphorylation. We'll talk more about these ideas as we move forward in our course.

What you'll notice is that, these stages that are labeled 1, 2, 3, and 4 are the main stages of aerobic cellular respiration. And so most of our attention is going to be focused on this region here of our map as we move forward in our course. But then we will also get to talk a little bit about some alternatives to the first stage of aerobic cellular respiration, some alternatives to glycolysis. That is going to be what is known as the PPP or the pentose phosphate pathway. We'll talk more about that. And then we'll also talk about the Etner-Doudoroff pathway or EDP here for short. Both of these alternative pathways to glycolysis are going to generate what is known as NADPH, but then they also are going to generate intermediates that will feed back into glycolysis, which is why we have arrows going from these alternative pathways back, leading back to glycolysis. We'll get to talk a lot more about these ideas as we move forward in our course.

Once we finish talking about aerobic cellular respiration on this left side over here, then we'll move on to talking about cellular respiration without oxygen. Once again, mainly talking about anaerobic respiration and fermentation. These are going to use alternative final electron acceptors that are not oxygen such as this nitrogen component here or this sulfur component over here. And then we'll also talk about different types of fermentation including lactic acid fermentation and alcohol fermentation. We're mainly going to be covering our lesson by following the leftmost branches first, and then we'll zoom out and talk about the right branches.

This here concludes our brief introduction to our map of the lesson on cellular respiration. Once again, feel free to use this map as a guide so that you can basically make predictions about what we're going to cover next and also to make sure that you are not lost within our lesson. I'll see you all in our next video.

Introduction to Aerobic Cellular Respiration Example 2

Alright. So here we have an example problem that says, using the map above, which of the following occurs in the absence of oxygen or where no oxygen is present? And we've got these 4 potential answer options down below. And so when we take a look at our map of the lesson on cellular respiration from up above, notice that this entire left hand branch over here is occurring in the presence of oxygen with oxygen being present. That's this entire left branch. And notice that the entire right branch is occurring without oxygen being present, in the absence of oxygen, and so that is this notice once again the problem is asking us, which of the following occurs in the absence of oxygen where no oxygen is present? So it specifically wants us to, choose an option on the right hand side of our map. And so when we look at some of these options such as aerobic respiration, oxidative phosphorylation, and oxygen serving as the final electron acceptor, notice that they all show up on the left hand side. Aerobic respiration is here, oxidative phosphorylation is here, and oxygen serving as the final electron acceptor is here. And so those three things are all occurring with oxygen being present, and the only one that occurs without oxygen being present is fermentation. And so fermentation, we can see over here on the right hand side, and there are 2 types that we're gonna talk about moving forward, lactic acid fermentation and alcohol fermentation. But for now, for this example problem, what we can see is that fermentation is going to be the correct answer here, the one that occurs in the absence of oxygen. And so we can go ahead and indicate that here is the correct answer to this example problem, and that concludes this example. So I'll see you all in our next video.

Based on the map of cellular respiration, why do we need to breathe in oxygen?

a) Oxygen is the final electron acceptor for lactic acid fermentation.

b) Oxygen is the final electron acceptor for alcohol fermentation.

c) Oxygen is the final electron acceptor for aerobic cellular respiration.

d) Oxygen is not important for the purposes of cellular respiration.

• A. Oxygen is the final electron acceptor for lactic acid fermentation.
• B. Oxygen is the final electron acceptor for alcohol fermentation.
• C. Oxygen is the final electron acceptor for aerobic cellular respiration.
• D. Oxygen is not important for the purposes of cellular respiration.

Here’s what students ask on this topic:

What is the overall chemical equation for aerobic cellular respiration?

The overall chemical equation for aerobic cellular respiration is:

$C_6{H}_{12}{O}_6+6O_2\to 6{\mathrm{CO}}_2+6H_{2}O+30–38\mathrm{ATP}$

This equation shows that glucose (C₆H₁₂O₆) and oxygen (O₂) are converted into carbon dioxide (CO₂), water (H₂O), and ATP, the energy currency of the cell.

What are the four stages of aerobic cellular respiration?

The four stages of aerobic cellular respiration are:

1. Glycolysis: Occurs in the cytoplasm and breaks down glucose into pyruvate, producing a small amount of ATP and NADH.
2. Pyruvate Oxidation: Converts pyruvate into acetyl-CoA in the mitochondria, producing NADH and releasing CO₂.
3. Krebs Cycle (Citric Acid Cycle): Occurs in the mitochondrial matrix, generating ATP, NADH, FADH₂, and releasing CO₂.
4. Electron Transport Chain and Chemiosmosis: Located in the inner mitochondrial membrane, it uses NADH and FADH₂ to produce a large amount of ATP through oxidative phosphorylation.

How is aerobic cellular respiration a redox reaction?

Aerobic cellular respiration is a redox reaction because it involves the transfer of electrons between molecules. In this process, glucose (C₆H₁₂O₆) is oxidized, meaning it loses electrons, while oxygen (O₂) is reduced, meaning it gains electrons. The overall reaction can be summarized as:

$C_6{H}_{12}{O}_6+6O_2\to 6{\mathrm{CO}}_2+6H_{2}O+30–38\mathrm{ATP}$

Here, glucose is oxidized to carbon dioxide (CO₂), and oxygen is reduced to water (H₂O).

What is the role of the mitochondria in aerobic cellular respiration?

The mitochondria play a crucial role in aerobic cellular respiration, especially in eukaryotic cells. Most stages of this process occur within the mitochondria, including:

• Pyruvate Oxidation: Converts pyruvate into acetyl-CoA in the mitochondrial matrix.
• Krebs Cycle (Citric Acid Cycle): Takes place in the mitochondrial matrix, generating ATP, NADH, and FADH₂.
• Electron Transport Chain and Chemiosmosis: Located in the inner mitochondrial membrane, it produces a large amount of ATP through oxidative phosphorylation.

The only stage that occurs outside the mitochondria is glycolysis, which takes place in the cytoplasm.

How does aerobic cellular respiration differ between eukaryotes and prokaryotes?

While the stages of aerobic cellular respiration are similar in both eukaryotes and prokaryotes, the locations where these stages occur differ:

• Eukaryotes: Most stages occur in the mitochondria. Glycolysis happens in the cytoplasm, while pyruvate oxidation, the Krebs cycle, and the electron transport chain occur in the mitochondria.
• Prokaryotes: Since they lack mitochondria, all stages occur in the cytoplasm or across the plasma membrane. Glycolysis, pyruvate oxidation, and the Krebs cycle occur in the cytoplasm, while the electron transport chain is located in the plasma membrane.