The food we ingest is not “ready to use,” our bodies need to process it so that theenergy and nutrients it contains are available to our cells. This processing involves a very complex series of chemical and biochemical reactions, which we globally refer to as metabolism, derived from a Greek word meaning “mutation,” indicating the transformation that food undergoes during these processes.
Heterotrophic metabolism and autotrophic metabolism: what is the difference?
Metabolic processes are not unique to our species: any organism – from animals to plants, to simpler organisms such as bacteria – needs to make use of them. One difference between our type of metabolism and that used by plants and some species of bacteria is the origin of the food source: heterotrophic metabolism, the one we humans use, is based on the intake of nutrients in the environment; plants, on the other hand, use the so-called autotrophic metabolism, that is, they are able to produce the nutrients necessary for their survival by themselves, using solar radiation as an energy source.
Catabolic and anabolic reactions
Speaking of energy use, and getting more specific about the issue, cellular metabolism is defined as the set of all catabolic and anabolic reactions that individual cells enact to ensure the survival of the entire organism. Catabolism is defined as all those processes from which structurally simpler molecules are obtained from complex polymers. Put another way, catabolic reactions are those in which the cell demolishes macromolecules to obtain the “building blocks” that constitute them: for example, from protein catabolism amino acidsAmino acids are the basic substances that make up proteins. Each protein is characterized by a precise sequence of amino acid "bricks". Some are produced by the body by processing food, others, which the body cannot synthesize, must be taken directly with food. are obtained, while from lipid catabolism fatty acids are recovered. Catabolic reactions are exoergonic, that is, they release energy. This “excess” energy is converted into ATPAdenosine triphosphate (ATP) can be defined as the "energy currency" of the cell, the instrument through which the cell carries out processes that require energy (endoergonic) and is produced by reactions that release energy (exergonic). (the energy exchange “currency” of all living things) and used by the cell to fuel anabolic processes, which are therefore endergonic, that is, they require energy to take place. Anabolism is the opposite of catabolism: through anabolic processes, the cell synthesizes complex molecules from simpler ones.
What are the differences between anabolism and catabolism?
Anabolism and catabolism, then, are the two sides of metabolism: while anabolism indicates a process of (re)construction (the prefix “ana” comes from a Greek preposition meaning “up”), catabolism, on the other hand, demolishes (“cata” comes from the Greek “to cast down, to demolish”).
The substantial difference between anabolism and catabolism is that the former includes reactions that require energy, the latter, in contrast, has to do with processes that release it. An example of an anabolic process is precisely the production of protein from amino acids. Synthesizing a protein is like making a necklace: you have to put individual beads together by joining them with a string. In the case of protein, the beads are the amino acids, and the thread that connects them is the chemical bonds (called peptide bonds) that connect them. The formation of each of these bonds requires a certain amount of energy (endoergonic process). Conversely, the catabolic process of degrading a protein (the breaking of our metaphorical necklace) splits peptide bonds between amino acids releasing energy (exoergonic process).
