How many ATP molecules are produced in pyruvate oxidation?
The net gain of high-energy compounds from one cycle is 3 NADH, 1 FADH2, and 1 GTP; the GTP may subsequently be used to produce ATP. Thus, the total yield from 1 glucose molecule (2 pyruvate molecules) is 6 NADH, 2 FADH2, and 2 ATP.
So essentially your cells are converting pyruvate into carbon dioxide using two different oxidation steps. During the first oxidation, one pyruvate will be converted into a molecule of acetyl CoA. Acetyl CoA is a product of sugar broken down which will be used in the second oxidation step.
- During glycolysis, two molecules of pyruvate are formed from one molecule of glucose. Glycolysis is the first step in cellular respiration. During aerobic respiration, there is an adequate oxygen supply and acetyl-coenzyme A is formed. The energy formed from aerobic respiration is used by the body.
- Under these conditions pyruvate undergoes a process termed fermentation, whereby pyruvate is reduced and NADH is oxidized to regenerate NAD+. The regeneration of NAD+ is critical for the ability of the cell to undergo additional rounds of glycolysis and to generate additional energy in the form of ATP.
- During the first stage of this process, glucose molecules break down into molecules of a carbon-based substance called pyruvate. If oxygen is not present, the respiration cycle does not continue past the glycolysis stage. This type of respiration--without oxygen--is known as anaerobic respiration.
Pyruvate oxidation steps
- A carboxyl group is removed from pyruvate and released as carbon dioxide.
- The two-carbon molecule from the first step is oxidized, and NAD+ accepts the electrons to form NADH.
- The oxidized two-carbon molecule, an acetyl group, is attached to Coenzyme A to form acetyl CoA.
- In the conversion of pyruvate to acetyl CoA, each pyruvate molecule loses one carbon atom with the release of carbon dioxide. During the breakdown of pyruvate, electrons are transferred to NAD+ to produce NADH, which will be used by the cell to produce ATP.
- Anaerobic processes do not require oxygen while aerobic processes do require oxygen. The Krebs cycle, however, is not that simple. It is a part of a complex multi-step process called cellular respiration. Although the use of oxygen is not directly involved in the Krebs cycle, it is considered an aerobic process.
- Glycolysis, the initial stage of glucose metabolism, takes place in the cytosol and does not involve molecular O2. It produces a small amount of ATP and the three-carbon compound pyruvate. In aerobic cells, pyruvate formed in glycolysis is transported into the mitochondria, where it is oxidized by O2 to CO2.
Yes, pyruvate oxidation happens in the mitochondrial matrix of eukaryotic cells. As soon as pyruvate enters the mitochondrial matrix in eukaryotes, it is oxidatively decarboxylated (with the help of the enzyme Pyruvate DeHydrogenase, PDH) to form Acetyl CoA (which is then free to act as a substrate in the Krebs cycle).
- In carbohydrate metabolism, acetyl CoA is the link between glycolysis and the citric acid cycle. The initiating step of the citric acid cycle occurs when a four carbon compound (oxaloacetic acid) condenses with acetyl CoA (2 carbons) to form citric acid (6 carbons).
- Afterwards, pyruvate is oxidized by continuously removing electrons in two distinct stages. The first oxidation step begins with one molecule of pyruvate and results in the production of CO2, electrons, and acetyl CoA. During the second step, called the Krebs cycle, one molecule of acetyl CoA is further oxidized.
- Each acetyl coenzyme A proceeded once through the citric acid cycle. Therefore, in total, it created 6 NADH + H+ molecules, two FADH2 molecules, four carbon dioxide molecules, and two ATP molecules. That's a lot of products!
Updated: 10th October 2018