Review of Aerobic Cellular Respiration - Online Tutor, Practice Problems & Exam Prep

Aerobic cellular respiration consists of four stages: glycolysis, pyruvate oxidation, the Krebs cycle, and oxidative phosphorylation. Glycolysis breaks down glucose into 2 pyruvate molecules, producing 2 ATP and 2 NADH. Pyruvate oxidation converts pyruvates into Acetyl CoA, yielding 2 NADH and releasing 2 CO₂. The Krebs cycle generates 2 ATP, 6 NADH, and 2 FADH₂, releasing 4 CO₂. Finally, oxidative phosphorylation produces 26-34 ATP and water, resulting in a total of 30-38 ATP from one glucose molecule, showcasing the efficiency of aerobic respiration.

Review of Aerobic Cellular Respiration

In this video, we're going to do a review of aerobic cellular respiration. And so really we're not going to cover any new information in this video. We're only going to review information that we've already covered in our previous lesson videos and recapping the most important takeaways. And so if you already feel really good about aerobic cellular respiration then feel free to skip this video. However, if you're struggling with aerobic cellular respiration even just a little bit, then feel free to stick around because we're going to recap aerobic cellular respiration here. Now that being said, recall that there are 4 stages of aerobic cellular respiration. And down below what we have is an image recapping all four stages of aerobic cellular respiration.

And so in aerobic cellular respiration recall that the vast majority of aerobic cellular respiration occurs in the mitochondria, and the mitochondria is this big pink thing that's in the background. And so the vast majority of cellular respiration does occur inside of the mitochondria. However, not all of cellular respiration occurs inside the mitochondria because the very first step of aerobic cellular respiration, which is glycolysis, actually occurs just outside of the mitochondria in the area of the cell known as the cytoplasm.

And so glycolysis again has the root glyco which means sugar and the root lysis which means to break down. And so glycolysis is going to break down a sugar, more specifically, it's going to break down the sugar, the monosaccharide, glucose, which has a total of 6 carbon atoms represented by these 6 black circles. And so ultimately these 6 carbon atoms of glucose are all going to be converted into carbon dioxide and exhaled out of our bodies. And so that's important to keep in mind about these 6 carbon atoms of glucose.

And so glycolysis is going to take glucose and break it up into 2 pyruvates. And additionally, it is also going to produce 2 NADH molecules which are electron carriers, full taxi cabs if you will, electron taxi cabs. And also glycolysis is going to produce a net of 2 ATPs produced via substrate level phosphorylation.

Now after these 2 pyruvates have been produced via glycolysis, those 2 pyruvates are going to be transported into the mitochondrial matrix, which is where pyruvate oxidation is going to occur. And so pyruvate oxidation is going to take these 2 pyruvates and it's going to oxidize those 2 pyruvates creating 2 more NADHs, 2 Acetyl CoA, and it's going to release 2 carbon dioxide or 2 CO₂ molecules. And so what you'll notice is that the 2 pyruvates, each of them have 3 carbon atoms. One of the carbon atoms on each pyruvate is going to be released as CO₂, and the other two carbon atoms are going to become part of the Acetyl CoA molecule.

Now after these 2 Acetyl CoA molecules have been produced, they are going to transition into the citric acid cycle or the Krebs cycle. And the Krebs cycle is ultimately going to produce, through both of the acetyl co a coming through, it's going to end up producing a total of 2 ATP molecules, a total of 2 FADH₂ molecules, and a total of 6 NADH molecules. And it's also going to release these 4 carbon atoms between both Acetyl CoAs as, 4 CO₂ molecules. And so these are the products of the citric acid cycle or the Krebs cycle.

And so ultimately, all 6 of the carbon atoms that originally came in as glucose were released as 6 carbon dioxide and so it's noticed that a total of 6 carbon dioxide is being released and exhaled. And so, all of the carbon atoms we followed, their path in this process for them to all get released. And so we're not gonna any, follow those carbon atoms any further instead of what we're going to do is follow these electron carriers that have been produced throughout this process. And so notice that, cumulatively there are a total of 10 NADH molecules that have been generated, and there's also a total of 2 FADH ₂s that have been created. So here is the total of these 3 processes, how many electron carriers they produced.

And so once again all of these electron carriers are going to make their way to the electron transport chain. And, after the electron transport chain builds up a hydrogen ion concentration gradient, chemiosmosis is going to allow for the production of lots and lots of ATP through oxidative phosphorylation. And so there's some 26 to 34 ATP molecules produced in this final stage of aerobic cellular respiration. And so 26 to 34 is the vast majority of the ATP because recall that the first three stages combined.

And so also in the electron transport chain, what's going to happen is there are going to be 6 oxygen gas molecules that are gonna act as the final electron acceptor in the electron transport chain, and those 6 oxygen gas molecules are going to react to form 6 water molecules. And so we have those here as well. And so when we're looking at the grand total of how many ATP molecules, aerobic cellular respiration produced, we need to consider the total amount of ATP produced by Oxidative Phosphorylation, which is some 26 to 34, and we also need to consider the ATPs produced via substrate level phosphorylation during the Krebs cycle or citric acid cycle and during glycolysis as well. And so basically what we have is 26+ 4 is going to give us a total of 30 ATPs at the minimum. And then, of course, 34 ATP plus, these 2 here is gonna give us a total of 38 ATP. And so the grand total amount of ATP between all of aerobic cellular respiration is somewhere between 30 to 38 ATP. And that is all from just one single glucose molecule that enters the cell, leads to some 30 to 38 ATPs. And so that's pretty efficient. From one glucose, you get 30 to 38 ATPs which are incredibly efficient. And so this here concludes our review of aerobic cellular respiration and we'll be able to get some practice applying these concepts as we move forward. So I'll see you all in our next video.

Through the first three stages of cellular respiration only 4 ATP molecules have been produced from the initial glucose molecule. In which of the products of these stages is the potential energy to produce more ATP molecules stored?

a) The 6 molecules of CO₂.

b) The H⁺ ions produced.

c) The 10 NADH and 2 FADH₂ molecules.

d) The 4 molecules of ATP.

• A. The 6 molecules of CO₂.
• B. The H⁺ ions produced.
• C. The 10 NADH and 2 FADH₂ molecules.
• D. The 4 molecules of ATP.

Total Products for Each Stage of Aerobic Cellular Respiration

In this video, we're going to continue our review of aerobic cellular respiration by filling in the table with the total products made from a single glucose molecule at each step of aerobic cellular respiration. And so, notice down below in this table what we have are the 4 stages of aerobic cellular respiration across the top. And so those are glycolysis, pyruvate oxidation, the Krebs cycle, or the citric acid cycle, and oxidative phosphorylation which includes the electron transport chain and chemiosmosis. And so, notice over here what we have are the start molecule, the number of carbon dioxide molecules or CO₂, the number of ATP molecules, the number of electron carriers including FADH₂ and NADH, and the ending molecule for the stage. And so when it comes to glycolysis, the start molecule is of course going to be a single glucose. So we can go ahead and put in glucose here. In terms of the amount of CO₂ molecules produced during glycolysis, it's actually going to be 0. And then in terms of the ATP molecules, glycolysis is going to produce a net of 2 ATPs. It produces 0 FADH twos, but it does produce 2 NADHs. And the ending molecule is really going to be 2 pyruvate molecules. And so really this is the summary of glycolysis.

So now moving on to pyruvate oxidation here, the start molecule for pyruvate oxidation is, of course, going to be the pyruvates that were generated in glycolysis. And so we can go ahead and put in 2 pyruvates here. In terms of carbon dioxide, each of these pyruvates is going to lose a carbon as a carbon dioxide molecule, and so there's going to be a total of 2 CO₂ molecules produced. In terms of ATP, it turns out that there's actually 0 ATPs made in pyruvate oxidation. There are also 0 FADH twos made in pyruvate oxidation, but there are 2 NADH molecules made in pyruvate oxidation. And so because pyruvate oxidation is the second stage, that's helpful to remember that it produces, it takes 2 pyruvates and converts them into 2 carbon dioxide, 2 NADHs, and 2 Acetyl CoA Molecules, and that is really the ending molecule of Pyruvate oxidation.

Now moving on, what we have is the Krebs Cycle or the Citric Acid Cycle. And of course, the starting molecule for the Krebs Cycle or the Citric Acid Cycle is going to be the ending molecule for the previous step which is 2 Acetyl Co~A, and so we can go ahead and put in 2 Acetyl CoAs here as the starting molecules, and each of these Acetyl CoA's has to undergo the Krebs cycle. And so there's going to be a cumulative total of 4 carbon dioxide molecules produced, a total of 2 ATP molecules produced, a total of 2 FADH₂ molecules produced, and a total of 6 NADH molecules produced. And, of course, the ending molecule is that, there, is no ending molecule. In fact, we could say that the ending molecule would just be oxaloacetate since that is the molecule that gets regenerated during the Krebs cycle or the citric acid cycle. But really the ending molecule is, a tough molecule because the cycle is a cycle that begins and ends with the same place. So ultimately, the cycle ends with oxaloacetate regeneration.

And so, this oxaloacetate is just going to continue to be part of another Krebs Cycle revolution or another Krebs Cycle reaction. And so, notice that all of the 6 carbon atoms of glucose were ultimately converted into carbon dioxide. So notice that there are 6 carbon dioxide that are being produced. And so now what we're going to do is essentially follow these electron carriers to the final step, which, is gonna be the electron transport chain in chemiosmosis, which performs oxidative phosphorylation. And so during oxidative phosphorylation, you could say that the starting molecules are going to be the electron carriers, such as, for example, NADH and FADH₂s. And so these NADH and FADH₂ electron carriers are going to drop off their electrons and ultimately in terms of carbon dioxide there are going to be 0 carbon dioxides produced during oxidative phosphorylation. In terms of ATP molecules, there's gonna be somewhere between 26 to 34 ATP molecules that are produced during oxidative phosphorylation. So notice the vast majority of ATP comes from the final stage here with oxidative phosphorylation. In terms of FADH twos and NADHs, they don't produce them, so there's gonna be 0. Instead, what they do is they consume those NADH and FADH twos by, taking their electrons. And then in terms of the ending molecule, what we could say is that it is going to be, water, H₂O. And, that's because recall that oxygen gas acts as the final electron acceptor and that oxygen gas reacts with hydrogen ions to form water. And so really this here, fills out our entire table and to get the totals, totals, all we need to do is fill in the rest of these columns here. And so notice that in terms of the totals for carbon dioxide, there are a total of 6 carbon dioxides that are being produced. And so the original 6 carbon atoms that were found in glucose were all ultimately converted into 6 CO₂ molecules, 6 carbon dioxide molecules. And these 6 carbon dioxide molecules are ultimately exhaled outside of our bodies. Now in terms of the total amount of ATP, what we have is somewhere between 30 to 38 total ATPs produced in aerobic cellular respiration. In terms of FADH twos, the total are going to be a total of 2. And in terms of NADHs, there's going to be a total of 10 NADHs that were produced. And so this here concludes and fills out our entire table here, which is really just reviewing the total products for each stage of aerobic cellular respiration. And so now that we filled out this table, we can now move on and apply some of the concepts that we've reviewed and some practice problems. So I'll see you all there.

Water is one of the products of aerobic cellular respiration. What is the source of the oxygen atom utilized to create the water molecules?

a) Carbon dioxide (CO₂).

b) Glucose (C₆H₁₂O₆).

c) Oxygen gas (O₂).

d) Pyruvate (C₃H₃O₃^–).

• A. Carbon dioxide (CO₂).
• B. Glucose (C₆H₁₂O₆).
• C. Oxygen gas (O₂).
• D. Pyruvate (C₃H₃O₃^–).

Approximately how many molecules of ATP are produced from the complete oxidation of one molecule of glucose (C6H12O6) through the process of aerobic cellular respiration?

a) 4.

b) 2.

c) 26-34.

d) 30-38.

• A. 4.
• B. 2.
• C. 26-34.
• D. 30-38.

Here’s what students ask on this topic:

What are the four stages of aerobic cellular respiration?

The four stages of aerobic cellular respiration are:

1. Glycolysis: This occurs in the cytoplasm and breaks down glucose into 2 pyruvate molecules, producing 2 ATP and 2 NADH.

2. Pyruvate Oxidation: This occurs in the mitochondrial matrix, converting pyruvate into Acetyl CoA, yielding 2 NADH and releasing 2 CO₂.

3. Krebs Cycle (Citric Acid Cycle): This also occurs in the mitochondrial matrix and generates 2 ATP, 6 NADH, and 2 FADH₂ while releasing 4 CO₂.

4. Oxidative Phosphorylation: This includes the electron transport chain and chemiosmosis, producing 26-34 ATP and water, utilizing NADH and FADH₂.

How many ATP molecules are produced in aerobic cellular respiration from one glucose molecule?

Aerobic cellular respiration can produce between 30 to 38 ATP molecules from one glucose molecule. This range accounts for the ATP generated during glycolysis (2 ATP), the Krebs cycle (2 ATP), and oxidative phosphorylation (26-34 ATP). The exact number can vary due to differences in the efficiency of the electron transport chain and the use of NADH and FADH₂ in oxidative phosphorylation.

What is the role of the electron transport chain in aerobic cellular respiration?

The electron transport chain (ETC) is the final stage of aerobic cellular respiration, located in the inner mitochondrial membrane. Its primary role is to transfer electrons from NADH and FADH₂ to oxygen, the final electron acceptor, through a series of protein complexes. This transfer creates a proton gradient across the membrane, which drives ATP synthesis via chemiosmosis. The ETC produces 26-34 ATP molecules and forms water as a byproduct.

What are the main products of the Krebs cycle?

The main products of the Krebs cycle (Citric Acid Cycle) are:

1. 2 ATP molecules

2. 6 NADH molecules

3. 2 FADH₂ molecules

4. 4 CO₂ molecules

These products are generated from the oxidation of Acetyl CoA and are crucial for the subsequent production of ATP in oxidative phosphorylation.

What is glycolysis and where does it occur?

Glycolysis is the first stage of aerobic cellular respiration, occurring in the cytoplasm of the cell. It involves the breakdown of one glucose molecule (6 carbons) into two pyruvate molecules (3 carbons each). This process produces a net gain of 2 ATP molecules and 2 NADH molecules. Glycolysis does not require oxygen and is the only stage of aerobic respiration that occurs outside the mitochondria.