Proteins

2024 Author: Jasmine Walkman | [email protected]. Last modified: 2023-12-16 08:29

Proteins are one of the main building blocks of living cells as well as viral particles. They have a complex spatial structure, while performing a variety of biological functions - from typically structural, protective, transport to catalytic and regulatory. Protein cannot be replaced by other components of food.

Their vital importance lies in their participation in the construction of all tissues and in all vital processes of the body: growth, development, metabolism, muscular and mental activity, reproduction.

The biological value of dietary proteins is determined by their amino acid composition. Proteins containing all amino acids in sufficient quantity for their own synthesis proteins, are called complete. Such are the proteins of animal origin.

Proteins of plant origin do not contain enough of all the essential amino acids. To ensure a balanced diet, they should be included in the menu proteins of both animal and vegetable origin. In this way, they complement each other.

Basic functions of proteins

- structural - they are the main building material for all cells, tissues and organs;

- biocatalyst - enzymes are highly organized protein bodies;

- regulatory - hormones are also proteins;

- protective - immunoglobulin antibodies are proteins;

- transport function - hemoglobin, myoglobin, ceruloplasmin, etc. are complex biopolymers.

The energy value of 1 gram of protein is equal to 4 kcal of energy.

Dietary amino acids proteins are divided into two major groups: irreplaceable and replaceable. Essential amino acids are so called because they cannot be synthesized in the body and a person is dependent on their import with food.

When the proteins in the food do not contain enough of even one of the essential amino acids, the synthesis of tissue proteins decreases sharply and there is an intensive breakdown of their own proteins. A negative nitrogen balance is established, which leads to stunted growth and development and weight loss.

Proteins are high molecular weight biopolymers with vital functions. The protein molecule is made up of amino acids and consists of various elements - carbon, nitrogen, oxygen, hydrogen, sulfur and others. Amino acids are the basic structural elements of proteins. Of the known about 80 amino acids, about 22, the most common in food, are important to humans.

Amino acids that cannot be synthesized by the human body and must be obtained through food are essential. These are: valine, leucine, isoleucine, threonine, phenylalanine, tryptophan, methionine, lysine. Histidine is added to them in childhood. Substituted amino acids can be synthesized from metabolic intermediates. Only the optimal ratio between essential and essential amino acids provides good protein synthesis in the body.

Protein deficiency

Most plant products are deficient in one, two or more essential amino acids, e.g. in wheat - lysine is deficient, in corn - tryptophan, in legumes - methionine and cystine. Healthy eating, however, requires taking both proteins of both animal and vegetable origin. The quality of the dietary protein is extremely important. It depends on the degree of usability of the protein taken with food from the body for its plastic needs.

Protein deficiency can have an extremely harmful effect on the human body. Prolonged lack of protein in the diet leads to increased protein breakdown (catabolism), reduced defenses, mental and physical performance. In children, growth and development are slowed down. Protein deficiency is often associated with a lack of energy components in the diet (low-calorie food) and this is the basis of protein-energy malnutrition.

Excessive protein intake

Excessive use of proteins or more precisely the protein foods make it difficult to digest. In the intestines, putrefactive processes intensify and toxic substances accumulate. Protein overdose leads to overload of the liver from breakdown products. Prolonged excess of protein in the diet leads to metabolic acidosis, overexcitation of the nervous system, metabolic disorders such as gout and others.

Sources of protein

Age, sex, body weight, physiological condition and characteristics of work determine a person's physiological need for quantity proteins. Energy intake of dietary proteins should make up 10-15% of the total dietary energy for the day. Dietary sources of protein are of animal and plant origin. With the highest biological value are foods of animal origin - eggs, milk, fish, meat. They contain proteins with balanced ratios of essential amino acids.