During one phase of aerobic respiration, pyruvate is oxidized in order to release energy. This lesson will discuss the various processes required to break down pyruvate and the resulting products that are formed.
Overview of Aerobic Respiration
Our cells constantly require energy to perform daily basic functions. Without energy, our cells could not keep us alive. So how do our cells get the energy we need to survive? The answer is aerobic respiration. Aerobic respiration is a process used by humans and other organisms to extract energy from the sugars that we eat.
This process is actually similar to how a car uses gasoline. Your car requires a fuel, like gasoline, to function. As your engine turns, the gasoline undergoes combustion, resulting in the release of energy. That energy is then used to power the car. In your cells, the sugar you eat serves as fuel for the cell. Aerobic respiration is the process of sugar combustion and results in the release of energy, which is used to power the cell.
Aerobic respiration creates energy by oxidizing sugar molecules. During an oxidation reaction, electrons are removed, causing the molecule to be broken down. The first stage of aerobic respiration begins by oxidizing sugar into two molecules of pyruvate. Pyruvate is the product derived from the initial breakdown of sugar. During the second stage, pyruvate will continue to be oxidized until it has become carbon dioxide (CO2). CO2 is the end product of the oxidation of sugar. Finally, your cells collect all the electrons that were removed and they’ll be used to make lots and lots of energy for the cell.
It turns out that one sugar molecule can produce up to 38 molecules of ATP. That’s just like getting a full tank of gas for just $1.00!
The Oxidation of Pyruvate
The oxidation of pyruvate is the second stage of aerobic respiration and is the focus of this lesson. This process, which occurs is two separate stages, continuously removes electrons from pyruvate until only carbon dioxide remains. 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.
Acetyl CoA is formed in three easy steps. First, a molecule of CO2 is removed from pyruvate. Then, some electrons are extracted and collected. Finally, a molecule of coenzyme A (CoA) is attached, resulting in the formation of acetyl CoA.
At this point, your cell is half way through the breakdown of pyruvate and has produced CO2, some electrons, and acetyl CoA.Once acetyl CoA has been formed, your cells are ready to proceed to the second phase of pyruvate oxidation, or the Krebs cycle. During the Krebs cycle, acetyl CoA will be oxidized by removing some electrons.
As acetyl CoA is broken down, a molecule of ATP is released in the process. Once acetyl CoA has been completely oxidized, all that remains is CO2. Therefore, the products of this second oxidation step are more electrons, two molecules of CO2, and one ATP.After both oxidation steps, neither pyruvate nor acetyl CoA exist anymore because we’ve stripped them of most of their electrons. All that remains from these molecules is the CO2.
Pyruvate was oxidized to acetyl CoA, then acetyl CoA was oxidized to form CO2.One thing to keep in mind is that we really start with two molecules of pyruvate, not one. Remember, one molecule of sugar produces two pyruvates. Therefore, everything we’ve discussed occurs to each molecule of pyruvate.
Each pyruvate goes through both oxidation steps. So the products of oxidation will actually be doubled because one sugar equals two pyruvates. For example, as both pyruvates go through the Krebs cycle, the products will actually be two ATP, twice as many electrons, and four molecules of CO2.
Your cells use aerobic respiration to power your body just like engines use gasoline to power cars.
First, one sugar molecule is converted into two molecules of pyruvate. 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. The results of this step include more electrons, two molecules of CO2, and one ATP.
During the final stage of aerobic respiration, all those harvested electrons are used to make lots of ATP.