What does protein consist of? Structure and amino acids

Protein is the foundation of life - universal building building material for cells, enzymes, hormones and support structures of tissues. Although we often associate them only with muscles and regeneration after exercise, the full image of protein shows its complex chemical structure, the variety of functions and key importance to health. That is why it is worth looking at what consist of protein molecules, which distinguish amino acids, and how the structure determines their action in the body.

This introduction introduces five areas that we will discuss in detail in subsequent sections: basic building building blocks of proteins, the division of amino acids into exogenous and endogenous, levels of the organization of protein structure, the denaturation process and its consequences, as well as the impact of structure on the absorption and use of proteins. Thanks to this, you will understand why protein is not a homogeneous component of the diet, but a set of various molecules with unique properties, as well as how to choose products and preparation methods to maximally use their nutritional potential.

Basic protein building blocks

Each protein consists of amino acids connected by peptide bonds in a polypeptide chain. The building blocks are 20 basic amino acids, differing in the R Side chain, which determines their properties - hydrophobic, hydrophilic, acidic or alkaline properties. Peptide binding arises as a result of a condensation reaction between one amino acid carboxyl group and the other amina group, releasing the water molecule.

The basic structural unit is an amino acid, consisting of a central carbon atom (α-carbon), to which amina (-nh₂), carboxyl (-cooh), hydrogen atom and a unique side chain (R) are attached. The variety of side chains determines the behavior of amino acids - e.g. glycine has the simplest chain (H), which gives it the greatest flexibility, while tryptophan or phenylalanine thanks to aromatic rings are more hydrophobic and often occur in the core of protein.

The amino acids connect into a polypeptide chain, which can have several dozen (hormones) to thousands (structural proteins) of amino acid residues. The order (sequence) is unique for each protein and genetically coded - it determines the method of folding the chain in space, and thus, its function. Already a slight change in the sequence (mutation) can change the properties of protein: enzymatic activity, ligand binding ability or thermal stability.

It is worth emphasizing that in human organisms there are not only enzymatic or structural proteins, but also regulatory (protein hormones such as insulin), transport (albumin, transferine), hardware (actin, muscle myosin) and immunological (antibodies). All of them are made of the same amino acid set, which illustrates, as the protein structure is universal and at the same time specialized.

Exogenous and endogenous amino acids

The division of amino acids into exogenous and endogenous results from whether the body can synthesize them by itself. Exogenous amino acids must be delivered with a diet, because man does not have enzymes necessary for their synthesis - including Leucine, isoleucine, valine (branched amino acids), lysine, methionine, phenylanine, treonine, tryptophan and histidine (in growth conditions). Their appropriate supply affects the full biological value of protein and effective tissue regeneration.

In contrast, endogenous amino acids can produce metabolic changes from other molecules by way. An example is Alanine, asparagin, glutamine or prolina. Although their synthesis is possible, in sickness states or intensive effort, demand can exceed the possibilities of biosynthesis, which is referred to as relatively necessary amino acids.

The correct ratio of exogenous amino acids to endogenous in the diet determines whether the protein consumed will be used efficiently. A deficiency of at least one exogenous amino acid - often called "limiting amino acid" - inhibits all protein synthesis, even if the others are abundant. Therefore, a diet based solely on a single source of protein (e.g. corn) can be defective, and the combination of various products (e.g. legumes with cereals) provides a full amino acid profile.

In clinical supplementation and nutrition, insulats or protein hydrolysates enriched with exogenous amino acids are often used in optimal proportions - an example is the amino acid profile in whey nutrients or BCAA mixtures (leucine, isoleucine, walina) supporting muscle regeneration after exercise.

Protein structure - levels

The organization of protein takes place at four levels of the structure: primary, secondary, tertiary and quuries. Each of them is responsible for the complexity of the shape and function of the molecule.

Primary This is a sequence of amino acids in a polypeptide chain. Its learning (sequence analysis) allows you to predict disulfide bonds and active regions of enzymes. Mutations in the primary structure can lead to leukemia (changes in hemoglobin) or granary diseases.

Secondary It arises as a result of hydrogen bonds between the groups -nh and -c = O in the main chain, creating characteristic elements: α-helisa and β-harmonie. α-Helisa is a spiral structure stabilized with hydrogen bonds every four amino acid residues, while β-harmonie is a simpler, zigzag form, where the neighboring chains are arranged in parallel or anti-agent.

Tertiary structure It is a spatial arrangement of the entire polypeptide chain, maintained by hydrophobic interactions, disulphide bridges, ionic and hydrogen bonds between the side chains of amino acids. They form the interior of the protein and determine the specific active pockets of enzymes or ligand binding.

Quaternary structure It occurs in proteins made of more than one polypeptide chain (subunits). For example, hemoglobin consists of four subunits - two α and two β - whose precise arrangement allows you to bind and transport oxygen. The breakdown of the Quaternary structures leads to the loss of functions, which is observed in the denaturation or mutations of oligomeric proteins.

Denaturation and protein functions

Denaturation is the process of irreversible (or partially reversible) distribution of higher protein structures (secondary, tertiary, quaternary) under the influence of physical factors (high temperature, UV radiation), chemical (acids, principles, principles, detergents) or biological (proteolithic ferments). Denaturation leads to the loss of biological function - softening, protein precision and lack of enzymatic activity.

In the kitchen, protein denaturation is a desirable phenomenon - when cooking eggs or meat, the protein is coagulated, which improves digestibility and destroys potential pathogens. However, in powdered protein supplementation (isolates, concentrates), minimal denaturation is taken care of to maintain biological activity of bioactive peptides. In industrial conditions, gentle spray drying and low -temperature ultrafiltration processes are used.

Denaturation is also used in laboratories-SDS-PAGE uses SDS detergent to break up protein structures, which allows you to analyze the molecular weight of individual subunits. In medicine, however, abnormal denaturation (misfolding) is the cause of prion or amyloidose diseases, where proteins accumulate in abnormal aggregates.

The impact of the structure on the absorption

The bioavailability of protein (bioavailability) depends on the ease of the distribution of peptide bonds and the availability of amino acid side chains for digestive enzymes. Proteins with a compact structure, such as collagen or keratin, are less digestible than relaxed proteins (whey, eggs), which is why collagen supplements often occur in the form of hydrolyzates - short peptides, which the body absorbs quickly.

Also, culinary processes affect the structure - cooking or fermentation improve digestibility, while highly processed proteins (hydrolysates too much processed) can lose bioactive effect. In products like a full -fledged meal of Smart Meal powder, enzymatic pretrability of protein is used to provide easily absorbable peptides with a diverse amino acid profile.

Studies on protein bioavailability are used by PDCAAS (Protein Digestibility Corrected Amino Acid Score) and Diaias (Digestible Indispensable Amino Acid Score). Higher values ​​indicate better digestibility and the use of exogenous amino acids. Whey and dairy products get the highest grades, while plant proteins, e.g. from peas or soy, require combining with other sources or processing to raise the result of the PDCAS.

Sources

• Harvard T.H. Chan School of Public Health - The Nutrition Source: Protein
• World Health Organization (WHO)/FAO - Protein and Amino Acid Requirements in Human Nutrition
• European Food Safety Authority (EFSA) - Scientific Opinion on Protein and Amino Acid Requirents
• Journal of the International Society of Sports Nutrition - "Protein Timing and Its Efists on Muscle Strength and Hyperrophy"
• Food Chemistry - "Effects of Processing on Protein Digestibility"
• National Institutes of Health (Nih) - Office of Dietary Supplements: Protein
• United States Department of Agriculture (USDA) - Fooddata Central

FAQ

How does protein denaturation during cooking affect their biological functions?

Denaturation during cooking leads to relaxation of the structures of secondary and tertiary protein, which facilitates digestive enzymes access to peptide chains. Thanks to this, digestibility increases, and the protein becomes more accessible to the body. However, excessive cooking can lead to oxidation and loss of some amino acids, which reduces nutritional value.

Can amino acid supplements improve the biological value of proteins in the diet?

Yes. The addition of exogenous amino acids (e.g. leucine, lysine) to meals poor in these ingredients increases their biological value and supports protein synthesis. In sports supplements, BCAA mixtures or amino acid profiles modeled on whey proteins are often used to optimize muscle regeneration.

What vitamins and minerals support protein synthesis in the body?

B vitamins (B₆, B₁₂, niacin) are cofactors of enzymes involved in the metabolism of amino acids. Zinc and magnesium support the functioning of ribosomes and the MRNA translation process into polypeptide chain. Deficiencies of these microelements can inhibit effective protein synthesis.

What is the different collagen and whey protein differently?

Collagen proteins have a triple Helisa built mainly of glycine, prol and hydroxyprol, which gives them mechanical strength, but makes them less digestible. Seering globular proteins are loosely rolled up, they are more easily denatured in the stomach and have a higher PDCaas indicator, which is why they provide exogenous amino acids faster.

Can probiotics support the digestion and absorption of amino acids?

Probiotics, especially Lactobacillus and Bifidobacterium strains, improve intestinal microflora, which may increase the activity of proteolytic enzymes and support the degradation of proteins to the amino acids. Studies indicate that probiotic supplementation can improve plant protein digestibility.