Types of Phosphorylation: Study with Video Lessons, Practice Problems & Examples

Aerobic cellular respiration generates ATP through two main types of phosphorylation: substrate-level phosphorylation and oxidative phosphorylation. The latter occurs in two steps: the electron transport chain (ETC) and chemiosmosis. The ETC utilizes oxidation-reduction (redox) reactions to create a hydrogen ion concentration gradient, which is essential for ATP synthesis during chemiosmosis. Together, these processes produce the majority of ATP in aerobic respiration, highlighting the significance of oxidative phosphorylation in cellular energy production.

Types of Phosphorylation

So recall from our previous lesson videos that the whole point of aerobic cellular respiration is to make a lot of ATP or energy for the cell. But really, during aerobic cellular respiration, the ATP that is being made can actually be made via 2 different types of phosphorylation. And so here in this video, we're introducing the types of phosphorylation that occur during aerobic cellular respiration. And those 2 different types of phosphorylation that create ATP during aerobic cellular respiration are number 1, substrate level Phosphorylation, and number 2, oxidative Phosphorylation. And so in our next lesson video, we'll introduce substrate level Phosphorylation, and then later in another video, we'll introduce oxidative phosphorylation.

So, I'll see you all in our next lesson video where we introduce substrate level phosphorylation.

Oxidative Phosphorylation

In this video, we're going to introduce oxidative phosphorylation, which is the second type of phosphorylation used to make ATP during aerobic cellular respiration. Now, in this video of oxidative phosphorylation, we're going to learn that it occurs in a 2-step process. The first step is going to be the electron transport chain or the ETC for short, and the second step is going to be chemiosmosis. Now, in this video we're not going to talk a lot of details about the electron transport chain or chemiosmosis. We're really only going to briefly mention these two, and later in our course, we'll talk a lot more details about both the electron transport chain and chemiosmosis, so keep that in mind.

And in this video really, there are only a few takeaways that you should get from this video. And so I'll make sure to make those few takeaways very clear by the end of the video. So oxidative phosphorylation, as its name implies with oxidative here, is going to use energy from oxidation-reduction reactions, or in short, redox reactions. These redox reactions are going to take place in the electron transport chain or the ETC, which once again we'll talk more details about the electron transport chain or the ETC later in our course in a different video. But ultimately, oxidative phosphorylation is going to use the energy from redox reactions that take place in the electron transport chain, and it's going to use that energy of the redox reactions to phosphorylate ADP and create a lot of ATP.

And so what we'll learn later in our course is that the electron transport chain is going to build a hydrogen ion concentration gradient, or an H⁺ concentration gradient. And the H⁺ concentration gradient is going to be used to make a large amount of ATP. And really, this is the biggest takeaway of this video: that oxidative phosphorylation is going to make a large amount of ATP, and the vast majority of ATP that's associated with aerobic cellular respiration. Now, once again, the electron transport chain is just part of oxidative phosphorylation, because oxidative phosphorylation consists of both the electron transport chain and this other process called chemiosmosis. And again, we're going to talk more details about the electron transport chain and chemiosmosis later in our course in a different video.

For now, here we're just briefly introducing these. And chemiosmosis is defined as the diffusion of ions, more specifically hydrogen ions, across a membrane down their concentration gradient from high to low concentration. And so technically, the electron transport chain and chemiosmosis combined allow for the process of oxidative phosphorylation, and we'll be able to see that down below in our image. So over here on the left-hand side of the image, notice that we're showing you a very complicated image of the electron transport chain and chemiosmosis. So we're not going to explain this image here in this video.

Again, we'll talk about the electron transport chain and chemiosmosis in more detail in a different video later in our course. For now, here this is just a foreshadowing image. Together, the electron transport chain, which builds a hydrogen ion concentration gradient, and chemiosmosis, which utilizes the concentration gradient to phosphorylate ADP and make a lot of ATP. These two processes combined, the ETC and chemiosmosis, allow for oxidative phosphorylation. And so this whole stage that you see here, this whole image you see here, is going to take place in the last stage of the aerobic cellular respiration.

And so here on the right-hand side, notice that we're showing you the 4 stages of aerobic cellular respiration. Notice that the first three stages, glycolysis, pyruvate oxidation, and the Krebs Cycle, are not involved directly with oxidative phosphorylation. And so the only stage that's directly involved with oxidative phosphorylation is this 4th and final stage, which actually consists of the electron transport chain and chemiosmosis. Two processes that we'll talk a lot more details about later in our course. But one of the biggest takeaways that you should get from this video is that together, the electron transport chain and chemiosmosis allow for oxidative phosphorylation.

And so ultimately, the electron transport chain and chemiosmosis, or in other words, oxidative phosphorylation, is what produces a large amount of ATP. And once again, this is probably the biggest takeaway of this video: That oxidative phosphorylation is going to generate a large amount of ATP. And once again, what we have is another image down below to just clarify the idea that oxidative phosphorylation consists of both the electron transport chain or the ETC and chemiosmosis together. And so if you have the electron transport chain and chemiosmosis, then the cell is able to perform oxidative phosphorylation.

And once again, we're going to talk a lot more details about the electron transport chain and chemiosmosis later in our course, and we'll talk more details about oxidative phosphorylation later in our course as well. But for now, the biggest takeaway that you should get from this video is that oxidative phosphorylation is going to occur in the 4th and final stage of aerobic cellular respiration and it's going to create a large amount of ATP, the vast majority of ATP that's associated with aerobic cellular respiration. And really, those are the 2 biggest takeaways of this video. And so once again, this here concludes our brief introduction to oxidative phosphorylation, and we'll talk a lot more about this much later in our course. And we'll be able to get some practice applying the concepts that we've learned as we move forward.

So I'll see you all in our next video.

Substrate-level phosphorylation is utilized to create ATP in which steps of aerobic cellular respiration?

• A. Electron Transport Chain and Chemiosmosis.
• B. Glycolysis and Pyruvate Oxidation.
• C. Pyruvate Oxidation and Krebs cycle.
• D. Glycolysis and Krebs cycle.

Which type of phosphorylation synthesizes ATP using an enzyme that transfers a phosphate group to ADP?

• A. Adaptive Phosphorylation.
• B. Oxidative Phosphorylation.
• C. Substrate-level Phosphorylation.
• D. Product-level Phosphorylation.

The largest amount of ATP made by cellular respiration is created by the process of ______________, in the _____________ steps of aerobic cellular respiration.

• A. Substrate-level phosphorylation; first.
• B. Oxidative phosphorylation; first.
• C. Oxidative phosphorylation; final.
• D. Substrate-level phosphorylation; final.

Here’s what students ask on this topic:

What are the two main types of phosphorylation in aerobic cellular respiration?

The two main types of phosphorylation in aerobic cellular respiration are substrate-level phosphorylation and oxidative phosphorylation. Substrate-level phosphorylation occurs directly in metabolic pathways like glycolysis and the Krebs cycle, where a phosphate group is directly transferred to ADP to form ATP. Oxidative phosphorylation, on the other hand, occurs in the mitochondria and involves the electron transport chain (ETC) and chemiosmosis. This process uses energy from redox reactions to create a hydrogen ion gradient, which drives the synthesis of ATP. Together, these processes are essential for producing the majority of ATP in aerobic respiration.

How does oxidative phosphorylation generate ATP?

Oxidative phosphorylation generates ATP through a two-step process involving the electron transport chain (ETC) and chemiosmosis. In the ETC, electrons are transferred through a series of protein complexes, which creates a hydrogen ion (H⁺) concentration gradient across the inner mitochondrial membrane. This gradient represents potential energy. During chemiosmosis, H⁺ ions flow back across the membrane through ATP synthase, a protein that uses the energy from this flow to phosphorylate ADP, forming ATP. This process produces the majority of ATP during aerobic cellular respiration.

What is the role of the electron transport chain in oxidative phosphorylation?

The electron transport chain (ETC) plays a crucial role in oxidative phosphorylation by creating a hydrogen ion (H⁺) concentration gradient across the inner mitochondrial membrane. It does this by transferring electrons through a series of protein complexes, which pump H⁺ ions from the mitochondrial matrix to the intermembrane space. This gradient represents stored energy, which is then used during chemiosmosis to drive the synthesis of ATP. The ETC is essential for the efficient production of ATP in aerobic cellular respiration.

What is chemiosmosis and how does it contribute to ATP production?

Chemiosmosis is the process by which hydrogen ions (H⁺) diffuse across a membrane down their concentration gradient, specifically through the enzyme ATP synthase. This diffusion occurs from the intermembrane space back into the mitochondrial matrix. The flow of H⁺ ions through ATP synthase provides the energy needed to phosphorylate ADP, forming ATP. Chemiosmosis is a critical component of oxidative phosphorylation and is responsible for producing the majority of ATP during aerobic cellular respiration.

What is the difference between substrate-level phosphorylation and oxidative phosphorylation?

Substrate-level phosphorylation and oxidative phosphorylation are two distinct methods of ATP production. Substrate-level phosphorylation occurs directly in metabolic pathways like glycolysis and the Krebs cycle, where a phosphate group is directly transferred from a substrate molecule to ADP, forming ATP. This process does not require oxygen. In contrast, oxidative phosphorylation occurs in the mitochondria and involves the electron transport chain (ETC) and chemiosmosis. It relies on oxygen and uses energy from redox reactions to create a hydrogen ion gradient, which drives ATP synthesis. Oxidative phosphorylation produces the majority of ATP in aerobic respiration.