WHAT IS THE METABOLISM OF LIVING BEINGS? - BIOLOGY - 2024

The metabolism of living beings is the set of chemical reactions that take place in the cells of the body. For example, through metabolism the human body transforms food into energy in order to function.

Metabolism is a continuous process that begins the moment we are conceived and ends the day we die. If the metabolism stops, the human being dies. The same applies to animals, plants and any other living being.

Respiration and photosynthesis

Let's take plants as an example to explain metabolism. Plant roots absorb water, mineral salts and other nutrients from the subsoil. These are transported through certain ducts present in the stem.

Upon reaching the leaves, the water combines with carbon dioxide, chlorophyll and chemical energy. In this way, photosynthesis occurs and carbohydrates (necessary for the operation of the plant) and oxygen (which is released) are produced.

Photosynthesis occurs without interruption in plants and is a metabolic process. Other examples of metabolism are respiration, cellular respiration, and digestion.

Stages of metabolism

Metabolism is a complex process made up of different stages. Broadly speaking, one can speak of the existence of two fundamental stages: one of synthesis and one of degradation. The synthesis stage is known as anabolism and the degradation stage is called catabolism.

Anabolism

Source: By Alejandro Porto, from Wikimedia Commons

Anabolism is the phase in which it is built. During this stage of metabolism, the organic matter that forms living things is created.

Thanks to this process, living things develop. For this reason, anabolic reactions occur with greater intensity in the growth stages of organisms.

Anabolism is composed of a series of chemical reactions that aim to synthesize complex substances from simpler molecules. These reactions are endergonic, which means that they consume energy to be carried out.

Anabolism not only creates substances that are used instantly, but also produce reserve substances, which are stored until the body needs them.

For example, plants make starch and animals make glycogen. In case it is necessary, each organism will take these substances and transform them into energy to be able to continue with the regular functioning.

Catabolism

Catabolism is the second major stage of metabolism. It is opposed to anabolism because it is a set of reactions in which organic matter is destroyed.

In other words, complex substances are broken down into much simpler substances. This process releases energy, so it is an exergonic reaction.

In addition to this, during catabolic reactions hydrogen atoms and electrons are eliminated in order to release energy. This means that there is an oxidation process. For this reason, oxygen plays an important role in catabolism.

The energy obtained by catabolic reactions is used by organisms to carry out their vital activities.

Carbohydrates, like glucose (sugar), are one of the substances that most break down for energy, since they are easy to break down.

Examples of metabolic processes

Some examples of metabolic processes are photosynthesis, digestion, and respiration.

Photosynthesis

Photosynthesis formula

Photosynthesis is a process that occurs in autotrophic organisms, which are those that are capable of producing their own food.

For this metabolic process to occur, it is necessary that three elements are present:

1. Sunlight, which is captured by the chlorophyll present in the chloroplasts of plant cells.
2. The water, which is absorbed by the roots and transported to the leaves by the ducts present in the stem of the plant.
3. Carbon dioxide, which is absorbed by the leaves.

Photosynthesis consists of two phases: a light phase and a dark phase. In the light phase, sunlight is transformed into chemical energy. In addition to this, the water molecules break down into hydrogen and oxygen (the latter is released into the atmosphere).

In the dark phase, the hydrogen atoms (coming from the water molecule) join with the carbon dioxide thanks to the chemical energy. This binding results in one glucose molecule and six oxygen molecules (which are released).

It should be noted that photosynthesis is carried out not only by higher plants, but also by brown and red algae (unicellular and multicellular) and by some bacteria.

Digestion

Digestion is a process that takes place in heterotrophic organisms, that is, those that cannot produce their own food. Instead, they consume matter already synthesized and from this they create new compounds.

The matter that heterotrophic organisms ingest can be plants or other consuming individuals. This is the method used by animals, fungi, and some bacteria.

In animals, two types of digestion are distinguished: extracellular and intracellular. Extracellular digestion occurs in the structures of the body suitable for this purpose: the stomach or the intestines.

Once food is ground up in the mouth and has passed through the digestive tract, it reaches the stomach and intestines. Here, food is chemically degraded (catabolism process).

When the extracellular digestion is complete, the intracellular digestion begins. The blood carries degraded nutrients, which it obtained thanks to intestinal absorption.

These nutrients are taken up by the cells, where other degradation reactions are carried out that generate energy for the proper functioning of these.

Breathing

Mitochondria

Respiration is a metabolic process that occurs in all living beings. This consists of two stages: cellular respiration and external respiration.

Cellular respiration occurs within the mitochondria, organelles of cells. These organelles capture oxygen and use it to extract energy from other molecules.

For its part, external respiration is the exchange of gases (carbon dioxide and oxygen) that occurs between the body and the environment.

References

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