We explain what catabolism is and its differences from anabolism. Also, the types that exist, importance and examples.
What is catabolism?
Catabolism is the process of breaking down complex nutrients into simple substances to obtain energy for the body. It is one of the two phases of the metabolism of living beings, the other being anabolism (a process opposite and complementary to catabolism).
This term comes from the Greek katos (“downward”) and ballein (“throw”), since it goes from the most complex and largest to the simplest and smallest. It requires a small energy contribution from the body but is releases chemical energy that the body stores in the form of ATP (Adenosine Triphosphate) to be used in other immediate processes.
Catabolic reactions, that is, those that make up catabolism, can be very different from each other, although at the same time they vary little between the various known forms of life. Generally consist of reduction-oxidation reactions of organic molecules although there are microorganisms capable of metabolizing iron and sulfur.
Catabolic reactions, in addition, are divided into those that require oxygen (aerobic) and those that do not (anaerobic). Both occur in the human body, for example, as digestion progresses (which breaks organic macromolecules into their constitutive monomers) and then the intracellular metabolic cycle (Krebs Cycle and Oxidative Phosphorylation).
See also: Aerobic respiration
Differences between catabolism and anabolism
Catabolism and anabolism are complementary but opposite processes. Catabolism breaks down organic macromolecules into simpler forms. Thus, it releases the chemical energy of its chemical bonds. Anabolism, on the other hand, consumes the body's energy to form new bonds and new complex molecules in the opposite direction.
Therefore, while one consumes energy, the other releases it ; While one goes from the basic to the complex, the other goes in the opposite direction. This means that when catabolism and anabolism are in balance, cells remain stable; but when it is necessary to break down tissues (such as “burning” fat), catabolism predominates over anabolism.
cellular catabolism
Catabolism takes place inside the body's cells through a series of processes that constitute cellular respiration. This occurs through different processes, depending on whether or not oxygen is present, but broadly speaking it consists of the oxidation of glucose biomolecules to obtain energy.
This process, called glycolysis, takes place in the cytosol of cells obtaining for each molecule of glucose (with 6 carbon atoms) two of pyruvate (with 3 carbon atoms each), in a process that invests two molecules of ATP to obtain four in exchange. Then, this pyruvate will be processed depending on whether or not oxygen is present in:
- cellular respiration. In the presence of oxygen (aerobic environment) pyruvate is oxidized to CO2, releasing the energy of its bonds to make ATP. This occurs in the matrix of the cell's mitochondria in its first phase (the tricarboxylic acid cycle or the Krebs Cycle) and then in the respiratory chain that occurs in the mitochondrial membranes. This process is highly productive from an energetic point of view and yields about 36 ATP molecules per glucose molecule.
- Cellular fermentation. When there is no oxygen present (anaerobic environment), organisms cannot oxidize pyruvate but instead ferment it, producing ethanol or lactic acid molecules instead of CO2. These molecules are much more difficult to eliminate and yield much less energy: only about 2 ATP molecules per glucose molecule.
Continue in: Glycolysis
muscle catabolism
It is called muscle catabolism. the reduction of muscle mass by the metabolism itself that is, the destruction of muscle tissue to obtain the necessary resources to feed.
This occurs when the food that enters the body is not enough to keep the metabolism going or when the energy demand is much higher than the amount of energy obtained from food.
In such cases, the body turns to the body's fats for additional energy to release and, once exhausted, resorts to desperate measures such as “burning” the muscles to ensure that the metabolism continues to work.
To avoid muscle catabolism, a diet appropriate to the amount of exercise must be maintained. or physical activity performed. In addition, it is important to provide the body with sufficient opportunities to rest since the greatest amount of muscle mass is created during sleep.
Importance of catabolism
Catabolism is a key part of the metabolic process of living beings that is, their methods of obtaining energy, especially in the case of heterotrophs, which must feed on the organic matter of other living beings, digesting it and breaking it down into minimal pieces useful for their organism.
Understanding catabolism It is essential to understand how and why we survive based on food consumption since our body must convert what we eat into useful pieces with which it must then make new cells and new tissues.
Example of catabolism
Catabolism It is the basic principle behind the digestion of the food we consume. For example, the food we eat is processed and broken down into its larger biomolecules, which enter the body to be catabolized.
Thus, proteins are broken down into amino acids, lipids into fatty acids and sugars into monosaccharides. These simpler compounds then converge on the same metabolic pathway: that of Acetyl CoA, the compound that enters cells to initiate cellular respiration (Krebs Cycle).
References
- “Catabolism” on Wikipedia.
- “Topic 16: Catabolism” in Biology Course.
- “Cellular catabolism: respiration” in Hypertexts in the area of biology.
- “Overview of metabolism: Anabolism and catabolism” (video) in Khan Academy Medicine.
- “Catabolism” in The Encyclopaedia Britannica.
- “Catabolism” in Biology Dictionary.
