Cellular breathing: what is, stages and types

Cellular breathing is a Series of metabolic reactions to obtain chemical energy in the form of ATPfrom the oxidation of organic molecules such as carbohydrates or sugars from food. Said easier, cellular breathing is the process by which the cell obtains energy.

It’s a Catabolic processthat is to say that large molecules degrade in small, while releasing energy. Here you can read about the difference between Anabolism and Catabolism.

For cellular respiration to be presented, certain cumulative and interdependent steps must occur. We will see that ATP occurs at each step, a molecule that provides energy for the activities that the cell must carry out. Several steps are used to make the most of the available molecules.

The stages of breathing are:

• Glycolysis: Glycolysis begins with the food we eat, specifically of the carbohydrates made of glucose. These carbohydrates are processed in the stomach and sent to the blood. With the help of insulin they are introduced to the cell, because here the glycolysis is carried out. Already in the cell, this glucose will be decomposed with the help of enzymes in a simpler molecule: pyruvate. Such a process also releases two ATP molecules, and NADH. In total, 2 pyruvates, 2 ATP and 2 NADH are obtained.
• Pyruvate oxidation: It happens in the mitochondrial matrix. In this cycle the pyruvate becomes by oxidation in acetyl-Coa, a smaller molecule, because it loses a carbon.
• Citric acid cycle or Krebs cycle: Acetyl co-a enters the mitochondria and will be used as energy in this cycle. It will degrade in GTP, FADH2, 3 NADH molecules, as well as depred 2 CO2 molecules as a secondary product. FADH2 and NADH will produce ATP.
• Oxidative phosphorylation: It also happens in the mitochondria. Here is an electron transport chain where several molecules transfer them from one place to another to release energy, to the final acceptor that can be oxygen or not. This makes an electrochemical gradient that stores energy to synthesize ATP. Thus, ATP is also produced here.

As you will see, throughout all stages many ATP are produced, thanks to the efficiency of the cell to manufacture energy through exogenous elements.

Cell breath can occur in presence or absence of oxygen. In this way we have two different types. Let’s review how it takes place for both cases.

Aerobic breathing

It is the one carried out by organisms that need oxygen to live, called aerobic organisms, which are for example animals. This breathing happens as we saw in the previous phase section, where glucose goes through glycolysis, by acetyl-CoA, the Krebs cycle and even oxidative phosphorylation. In this last phase is where it comes into play Oxygenspecifically as the final acceptor of the external electron transport chain. This oxygen is the one we breathe, so we can understand that when we breathe we are helping our cells to manufacture energy.

The aerobic cell breathing process can be summarized in the following equation:

C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + 36 ATP

This equation expresses that a glucose (C6H12O6) will result in 6 CO2, 6 water and 36 ATP molecules. This water as an internal breathing by -product only occurs in aerobics. Let’s see what are the other differences between both types of breaths.

Anaerobic breathing

This is the second type of internal or cellular breathing, and happens under conditions lacking oxygen. It is frequently used as a synonym for fermentation, but we clarify that they are two opposite concepts.

Here is the same steps of the previous section, but Without oxygen. Instead, another molecule other than oxygen as an external acceptor is used. In this case, the USA electron transport chain of final acceptor to nitrate, sulphide, sulfur, methane, hydrogen, among other different acceptors. It happens in prokaryotic organisms such as bacteria or arches.

The essential difference between fermentation and anaerobic breathing is that in the first there is no electron transport chain or krebs or citric acid cycle, and therefore should not be used as equal concepts.

As you know the process of cellular respiration better, now we encourage you to read about the phases of the cell cycle.

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