Pyruvate Oxidation - Online Tutor, Practice Problems & Exam Prep

Pyruvate oxidation, the second step of cellular respiration, occurs in the mitochondrial matrix after glycolysis produces 2 pyruvate molecules. This process converts each pyruvate into 2 acetyl CoA, 2 NADH, and 2 CO₂ molecules. During oxidation, pyruvate loses electrons, which are accepted by NAD⁺, forming NADH. Each pyruvate, containing 3 carbon atoms, releases one carbon as CO₂, while the remaining carbons form acetyl CoA, which enters the Krebs cycle for further energy production.

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 produced during glycolysis are then transported to the mitochondrial matrix. In the mitochondrial matrix, the second stage of cellular respiration will occur. Pyruvate oxidation is the second step of cellular respiration and will convert each of the pyruvate molecules. Once again, pyruvate oxidation occurs in the mitochondrial matrix. Because pyruvate oxidation is the second step of cellular respiration, it is easy to remember that pyruvate oxidation produces 2 acetyl CoA molecules, 2 NADH molecules, and 2 CO₂ (carbon dioxide) molecules just from 1 glucose that originally enters the cell.

Down below in our image, we show 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. Recall glycolysis results in the production of 2 pyruvate molecules which end up getting transported to mitochondria, with the mitochondria in the background right here.

In another image showing more details of pyruvate oxidation, we see that pyruvate, the molecule it starts with, gets oxidized, meaning pyruvate loses electrons. When pyruvate loses electrons, NAD⁺ gains these electrons to become NADH. Pyruvate oxidation produces 2 NADH. Also, note that each of these black circles in the pyruvates represents carbon atoms; each pyruvate has 3 carbon atoms. One carbon atom from each of the pyruvates is lost as a CO₂ molecule, and so 2 CO₂ molecules get produced. The remaining carbons of the pyruvate get attached to 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 CO₂s, and 2 acetyl CoA's. Because pyruvate oxidation is the second step of cellular respiration, that makes it easy to remember that it produces 2 NADHs, 2 CO₂s, and 2 acetyl CoA's.

This concludes our introduction to pyruvate oxidation. The 2 Acetyl CoA's produced make their way to the third step of cellular respiration, which is the Krebs cycle. We'll talk about that as we move forward in our course. 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, NADH, and CO₂. Specifically, pyruvate loses electrons, which are gained by NAD⁺ to form NADH. Each pyruvate, containing three carbon atoms, releases one carbon as CO₂, while the remaining carbons form acetyl CoA. This acetyl CoA then enters the Krebs cycle for further energy production.

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, releases one carbon as CO₂, while the remaining carbons form acetyl CoA. Additionally, NAD⁺ is reduced to NADH during this process. These products are crucial for the subsequent steps in cellular respiration, particularly the Krebs cycle.

How does pyruvate oxidation contribute to the Krebs cycle?

Pyruvate oxidation contributes to the Krebs cycle by producing acetyl CoA, which is essential for the cycle to proceed. Each pyruvate molecule is converted into one acetyl CoA, which then enters the Krebs cycle. This cycle is a series of reactions that generate high-energy electron carriers (NADH and FADH₂) and ATP, which are vital for the cell's energy production. Without acetyl CoA from pyruvate oxidation, the Krebs cycle cannot function effectively.

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, NAD⁺ is reduced to NADH by gaining electrons. These high-energy electrons carried by NADH are later used in the electron transport chain to produce ATP, the primary energy currency of the cell. Thus, NADH is essential for the efficient production of ATP during cellular respiration.

What happens to the carbon atoms in pyruvate during pyruvate oxidation?

During pyruvate oxidation, each pyruvate molecule, which contains three carbon atoms, undergoes decarboxylation. One of the three carbon atoms is released as a molecule of CO₂. The remaining two carbon atoms are then attached to coenzyme A to form acetyl CoA. This process occurs for each of the two pyruvate molecules produced from one glucose molecule during glycolysis, resulting in the release of two CO₂ molecules and the formation of two acetyl CoA molecules.