Pyruvate Oxidation - Online Tutor, Practice Problems & Exam Prep

Pyruvate oxidation, the second step of cellular respiration, occurs in the mitochondrial matrix, converting 2 pyruvate molecules from glycolysis into 2 Acetyl CoA molecules. This process also produces 2 NADH and 2 CO₂ molecules. During oxidation, pyruvate loses electrons, which are accepted by NAD⁺, forming NADH. Each pyruvate, containing 3 carbon atoms, loses one carbon as CO₂, while the remaining carbons attach to CoA. The resulting Acetyl CoA enters the Krebs cycle, continuing the energy extraction process from glucose.

Pyruvate Oxidation

In this video, we're going to begin our introduction to pyruvate oxidation. First, we need to recall from our previous lesson videos that the first stage of cellular respiration, or glycolysis, results in the production of 2 pyruvate molecules. These 2 pyruvate molecules that are produced during glycolysis are then transported to the mitochondrial matrix. In the mitochondrial matrix, this is where the second stage of cellular respiration will occur. Pyruvate oxidation, the second step of cellular respiration, is going to convert each of the pyruvate molecules that were produced into a molecule known as Acetyl CoA. Once again, pyruvate oxidation occurs in the mitochondrial matrix. Pyruvate oxidation, being the second step of cellular respiration, makes it easy to remember that it produces 2 acetyl co a molecules, 2 NADH molecules, and 2 CO₂ or carbon dioxide molecules just from 1 glucose that originally enters the cell.

What we can see down below in our image is that we are showing you the 4 stages of aerobic cellular respiration. In our previous lesson video, we already covered glycolysis, so we can go ahead and give this a check. Glycolysis, again, results in the production of 2 pyruvate molecules which end up getting transported to the mitochondria, which is in the background right here.

Down below, we have another image showing more details of what implies with pyruvate oxidation. Pyruvate, the molecule that it starts with, is going to end up getting oxidized, which means that pyruvate is going to lose electrons. When pyruvate loses electrons, what ends up gaining the electrons are these NAD⁺, which become NADH when they gain the electrons. Pyruvate oxidation produces 2 NADH. Also, notice that each of these black circles in the pyruvates represents carbon atoms, and each pyruvate has 3 carbon atoms. Notice that one of the carbon atoms from each of the pyruvates is going to get lost as a CO₂ molecule, and so 2 CO₂ molecules get produced and these CO₂ carbons get converted into CO₂. The other carbons of the pyruvate end up getting attached to these CoA molecules. You can see one molecule of Acetyl CoA here and the second molecule of Acetyl CoA here. Ultimately, pyruvate oxidation produces 2 NADH, 2 CO₂, and 2 acetyl co a's. It's helpful to know that because pyruvate oxidation is the second step of cellular respiration, the second step, that makes it easy to remember that it produces 2 NADHs, 2 CO₂s, and 2 acetyl CoAs.

This here concludes our introduction to pyruvate oxidation, and you can see that these 2 acetyl CoAs that are produced are going to make their way to the 3rd step of cellular respiration, which is the Krebs cycle. We'll get to talk about that as we move forward in our course. So, I'll see you all in our next video.

Each of the following describes the pyruvate oxidation reaction except that _____________________.

a) It connects glycolysis to the citric acid cycle.

b) Each pyruvate is converted to an acetyl-CoA molecule.

c) NAD⁺ is reduced to NADH.

d) This reaction occurs within the cytoplasm.

e) Carbon dioxide is released as a by-product.

• A. It connects glycolysis to the citric acid cycle.
• B. Each pyruvate is converted to an acetyl-CoA molecule.
• C. NAD⁺ is reduced to NADH.
• D. This reaction occurs within the cytoplasm.
• E. Carbon dioxide is released as a by-product.

In aerobic cellular respiration, pyruvate molecules must be transformed through a process called pyruvate oxidation before they can be broken down in the Krebs Cycle. What are the products of pyruvate oxidation?

a) Acetyl CoA, O₂, and ATP.

b) Acetyl and CO₂.

c) Acetyl CoA, FADH₂, and CO₂.

d) Acetyl CoA, NADH, and CO₂.

e) Acetyl CoA, NAD⁺, ATP, and CO₂.

• A. Acetyl CoA, O₂, and ATP.
• B. Acetyl and CO₂.
• C. Acetyl CoA, FADH₂, and CO₂.
• D. Acetyl CoA, NADH, and CO₂.
• E. Acetyl CoA, NAD⁺, ATP, and CO₂.

Here’s what students ask on this topic:

What is pyruvate oxidation and where does it occur?

Pyruvate oxidation is the second step of cellular respiration, following glycolysis. It occurs in the mitochondrial matrix. During this process, each pyruvate molecule produced from glycolysis is converted into Acetyl CoA. This conversion also results in the production of NADH and CO₂. Specifically, pyruvate loses electrons (is oxidized), which are accepted by NAD⁺ to form NADH. Each pyruvate, containing three carbon atoms, loses one carbon as CO₂, while the remaining carbons attach to CoA to form Acetyl CoA. The Acetyl CoA then enters the Krebs cycle for further energy extraction.

What are the products of pyruvate oxidation?

Pyruvate oxidation produces three main products per glucose molecule: 2 Acetyl CoA, 2 NADH, and 2 CO₂. Each pyruvate molecule, containing three carbon atoms, loses one carbon as CO₂, while the remaining two carbons attach to CoA to form Acetyl CoA. Additionally, during the oxidation process, electrons are transferred to NAD⁺, forming NADH. These products are crucial for the continuation of cellular respiration, as Acetyl CoA enters the Krebs cycle, and NADH is used in the electron transport chain to generate ATP.

How does pyruvate oxidation contribute to cellular respiration?

Pyruvate oxidation is a critical step in cellular respiration as it bridges glycolysis and the Krebs cycle. By converting pyruvate into Acetyl CoA, it prepares the substrate for the Krebs cycle, where further energy extraction occurs. Additionally, the process produces NADH, which carries high-energy electrons to the electron transport chain, contributing to ATP production. The CO₂ released during pyruvate oxidation is a waste product that is expelled from the cell. Overall, pyruvate oxidation ensures the efficient continuation of cellular respiration, maximizing energy extraction from glucose.

Why is NADH production important in pyruvate oxidation?

NADH production during pyruvate oxidation is crucial because NADH serves as an electron carrier in cellular respiration. When pyruvate is oxidized, it loses electrons, which are accepted by NAD⁺, forming NADH. These high-energy electrons carried by NADH are later used in the electron transport chain to generate ATP, the cell's primary energy currency. Without the production of NADH, the electron transport chain would lack the necessary electrons to drive ATP synthesis, significantly reducing the cell's energy production efficiency.

What happens to the Acetyl CoA produced in pyruvate oxidation?

The Acetyl CoA produced in pyruvate oxidation enters the Krebs cycle, also known as the citric acid cycle. In the Krebs cycle, Acetyl CoA combines with oxaloacetate to form citrate, which undergoes a series of enzymatic reactions. These reactions result in the production of ATP, NADH, and FADH₂, as well as the release of CO₂. The NADH and FADH₂ produced carry high-energy electrons to the electron transport chain, where they are used to generate additional ATP. Thus, Acetyl CoA is essential for the continuation of cellular respiration and energy production.