Proteins: what they are and how they influence the functioning of the body

Proteins are biomolecules made up mainly of carbon, hydrogen, oxygen, and nitrogen.. These are not its only components, as certain protein structures can contain sulfur, phosphorus, iron, magnesium, copper and other chemical elements.

From a physiological point of view, proteins are the main components of the cell, which is why they are needed to tissue repair, growth, cell division and many other functions related to the physical structure of beings alive.

For this reason, it is not surprising that 10 to 15% of the diet of any human being should be made up of protein. Fortunately, these essential macromolecules for life are found in multiple foods: salmon, eggs, milk, legumes, beef, and a long list of foods.

Due to the physical and nutritional importance of these biomolecules, we find it necessary to investigate the morphology, properties and necessary intake of proteins. Continue with us on this journey through various biochemical concepts, as we assure you that some of the data in the following lines will surprise you.

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Related article: "Macronutrients: what are they, types and functions in the human body"

What are the characteristics of proteins?

To whet your appetite, we are going to present you a series of data that frames the world of proteins on a more tangible and objective plane. Let's go there:

Proteins represent approximately 50% of the dry weight of the tissues of living beings.
An adult individual needs to ingest one gram of protein per day for every kilo of weight.
The amino acids that make up proteins are encoded in the standard genetic code, common to all living beings.
One gram of protein provides 4 kilocalories of energy.
The human body has about 100,000 types of proteins, all of them necessary for the performance of vital functions.

As we can see, proteins are governed by a universal language (the genetic code) and make up the different structures of all living things that surround us. Even so, we have introduced a term that we have to explain in depth, since the protein structure cannot be understood without it: we have to talk about the amino acid.

Amino acids and their importance

An amino acid is defined as each of the basic units that make up proteins. Its chemical structure is based on a central carbon molecule, an amino group, a carboxyl group, a hydrogen atom, and a variable chemical radical. Thus, we are facing a kind of chemical "cross" with a tetrahedral structure in the three-dimensional plane.

There are 20 different amino acids, which are joined in different orders by peptide bonds to give rise to proteins (polypeptide chains) present in nature. Summarizing this terminological conglomerate in a basic simile, it is as if we were using the same pieces of a puzzle to create a painting different each time: the results are very different from each other due to the order of the individual components, but the base material is the same. In this case, it is clear that the order does alter the product.

We can distinguish two types of amino acids: essential and non-essential. The essentials are those that cannot be synthesized by the body and therefore must be ingested through the diet. It should be noted that the "essentiality" of each of them depends on the taxon of living being that we look at, since the different metabolic routes of the species make that some need certain compounds that others do not.

On the other hand we have non-essential amino acids, those that we can synthesize within our body (mainly in the liver) from intermediates by transamination, and which are therefore not strictly necessary in the diet. In last place are the conditionally essential amino acids, that is, those that are required in the daily intake in certain settings and specific situations.

Finally, and after this very brief review of the world of amino acids, it is necessary to emphasize that the nutritional quality of a protein is encoded by the number of essential amino acids that is present in its chemical structure, in addition to the digestibility of its components and the proportion retained by the body.

You may be interested in: "Carbohydrates: what are they, types and characteristics of these molecules"

Protein structure

Describing the structural complexity of proteins as we have done with amino acids is a practically impossible task, since the writing space is finite and there is a lot of ground to encompass. It is enough to know that all proteins have the same central chemical skeleton, that is, a linear chain of various amino acids. This is called "primary structure", and it is what mainly determines the nature and function of the protein in the body.

The thing is much more complicated, because due to the folding of the macromolecule, its disposition three-dimensional and many other factors, proteins also have tertiary, secondary and quaternary.

Features

All proteins perform essential functions for cell development and maintenance, but we can combine the tasks of these biomolecules in the following points:

Catalysis: enzymes are commonly proteins, so we can say that they are responsible for carrying out multiple chemical reactions in our body.
Regulatory: Hormones are proteins. These are responsible for maintaining the balance of our body, among many other behavioral and physical functions.
Protective: Immunoglobulins (antibodies) are protein in nature, which is why their immune function is vital.
Structural: collagen, tubulin, keratin and many other protein compounds make up the physical structures that characterize us as organisms.

We could continue listing functions for days, since some proteins (by themselves or associated with other compounds) They are transporters of substance through the bloodstream, they have motor functions, they give coloring to living beings, they are an energy reserve and many more functionalities. In summary: practically all biological processes require the presence of proteins.

Proteins and nutrition

The World Health Organization (WHO) and the Food and Agriculture Organization of the United Nations (FAO) indicate that 10 to 15% of an individual's necessary daily energy must come from proteins directly. This value varies depending on the needs and requirements of the person in question, because for For example, an athlete with high muscle development may need to increase this intake to 35%.

But beware: medical organizations like the Mayo Clinic advise us that consuming more than two grams of protein per kilo of weight of the individual begins to be excessive, which can translate into liver and kidney problems in the long run term. In any case, this type of pathology should not concern the general population, since consuming such a high percentage of protein is practically impossible unless supplements are used.

Contrary to what certain sectors of the population believe, not only meat and animal products have protein. For example, 100 grams of lentils have 9 grams of pure protein. It is true that meat has a higher proportion (25 grams per 100 grams of fillet), but it is possible to obtain all the necessary protein intake without resorting to meat products.

Protein is present in a wide range of foods, whether of animal or plant origin: fish, red meat, chicken, turkey, eggs, milk, nuts, soy, oatmeal and many others more food. So that, the source of obtaining and the modulation of the diet based on protein intake completely depends on the values and needs of each one.

Resume

As we have seen, there is enough information available on proteins to write several books. From a biological point of view they make up the majority of the organic components of the tissues of living beings and fulfill a number of countless functions in our body. They also have a characteristic structure based on amino acids, universal compounds that encode their functionality and nature according to the order they present in the linear chain.

Finally, we have also shown you the importance of protein intake in the human diet and what foods are rich in it. Of course, we are facing a biomolecule and macronutrient (along with fats and carbohydrates) without which we could not live.

Bibliographic references:

Are you consuming too much protein? Mayoclinic. Picked up on October 13 in https://newsnetwork.mayoclinic.org/discussion/esta-consumiendo-demasiada-proteina/
Some facts about proteins, radychildren.org (San Diego Hospital). Picked up on October 13 in https://www.rchsd.org/health-articles/algunos-datos-sobre-las-protenas/
Guidelines on Nutrition Labeling (FAO). Picked up on October 13 in http://www.fao.org/ag/humannutrition/33311-065a023f960ba72b7291fb0bc07f36a3a.pdf
FAO and WHO present an expert report on diet, nutrition and prevention of chronic diseases (WHO). Picked up on October 13 in https://www.who.int/mediacentre/news/releases/2003/pr32/es/#:~:text=La%20ingesta%20de%20prote%C3%ADnas%20recomendada, and% 20el% 20control% 20del% 20weight.
Proteins, Nutrition and Dietetics Manual of the Complutense University of Madrid. Picked up on October 13 in https://www.ucm.es/data/cont/docs/458-2013-07-24-cap-5-proteinas.pdf
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Suárez López, M. M., Kizlansky, A., & López, L. B. (2006). Evaluation of the quality of proteins in food by calculating the amino acid score corrected for digestibility. Hospital Nutrition, 21 (1), 47-51.