Aminokyseliny: Podstata, druhy a funkce

Amino acids are nitrogen-containing organic compounds with a diverse yet similar structure. They are the monomers that make up peptides and proteins through peptide bonds. In the human body, amino acids are involved in the synthesis of enzymes, hormones, neurotransmitters, and tissues.

These compounds have a common molecular structure, which is why they belong to a distinct group of organic compounds.

Their structure consists of a central carbon atom (C), to which four different groups are attached: an amino group (–NH₂), a carboxyl group (–COOH), a hydrogen atom, and a side chain (R-group), which is different for each amino acid and determines its chemical properties and functions. 

It is the variety of R-groups that accounts for the differences between individual amino acids.

Amino acids play a fundamental role in the normal functioning of the body. They are the basic building blocks of proteins, which make up tissues, enzymes, hormones, and immune molecules. Without them cell division, repair, or maintaining vital processes is not possible.

Protein synthesis and tissue growth

All tissues in the body are built and maintained by proteins synthesized from amino acids. This is especially important during growth, wound healing, recovery after surgery, and muscle injuries.

Energy supply during exertion

During prolonged physical exertion, some amino acids (especially branched-chain amino acids – BCAA) are used as an energy source when glycogen stores are depleted. This helps endurance and delays fatigue, and they are often used as a means to preserve muscle mass during a calorie deficit.

Recovery after physical exertion

Amino acids accelerate muscle fiber regeneration after exercise or injury. This reduces pain, restores muscle function, and prevents muscle mass loss during stressful conditions. This is why amino acids are specifically taken for muscles.

Hormonal and enzyme synthesis

These organic compounds participate in the production of hormones like insulin, thyroxine, and adrenaline, as well as enzymes that regulate nearly all biochemical reactions in the body. These are just some of the substances they build in the body.

Support for the immune system

Glutamine and other amino acids serve as fuel for immune cells and maintain the barrier function of the intestines, which is critical in preventing infections and inflammation. They also build specific antibodies and immunological molecules and active complexes to fight pathogens.

Participation in neurotransmitter synthesis

Amino acids like tryptophan, tyrosine, and glutamate are precursors to neuromediators – substances that regulate mood, sleep, attention, and other brain functions.

Detoxification and nitrogen balance

The liver uses amino acids in the processes of detoxifying ammonia and other toxins. They also play a role in maintaining the balance of nitrogen compounds in the body.

Improvement of digestion

By building digestive enzymes and maintaining the intestinal lining, amino acids contribute to the optimal absorption of nutrients and protect the gastrointestinal barrier.

Amino acids are divided into two main groups: essential(indispensable) and non-essential (replaceable).

Essential amino acids cannot be synthesized by the human body and must therefore be obtained through food. In contrast, non-essential amino acids can be formed internally – as a result of metabolic processes from other amino acids or nitrogen-containing compounds.

In total, 21 amino acids participate in the construction of structures in the human body. Of these, 9 are essential, while the remaining 12 the body can produce on its own through endogenous synthesis from various precursors.

Essential amino acids (indispensable)

These are amino acids that the body cannot produce on its own and must be obtained through food.

There are 9 essential amino acids, each with a specific role:

• Histidine:Necessary for tissue growth and repair, involved in hemoglobin production, and crucial for maintaining the myelin sheaths of nerve cells. A precursor to histamine – an important mediator in immune response and gastric acid secretion.

• Isoleucine:A branched-chain amino acid (BCAA), involved in hemoglobin synthesis, regulates energy metabolism, and aids muscle recovery after exertion.

• Leucine: Also a BCAA, a highly anabolic amino acid, activates the mTOR pathway – a key signaling mechanism for muscle growth and protein synthesis.

• Lysine: Important for collagen synthesis, calcium absorption, and the production of enzymes and hormones. Supports immune function and tissue repair.

• Methionine: Sulfur-containing amino acid necessary for the synthesis of creatine, carnitine, and glutathione. Participates in DNA methylation and fat and toxin metabolism in the liver.

• Phenylalanine:Precursor to tyrosine, which is used for synthesizing dopamine, adrenaline, and thyroxine. Key for neurotransmitter balance and brain function.

• Threonine: Involved in the construction of structural proteins like collagen and elastin. Supports skin and digestive tract health.

• Tryptophan: Precursor to serotonin and melatonin – important for mood, sleep, and mental health. Also participates in the synthesis of niacin (vitamin B3).

• Valine:The third branched-chain amino acid, essential for muscle metabolism, tissue regeneration, and maintaining energy balance during physical exertion.

Non-essential amino acids (replaceable)

These amino acids are synthesized by the body, but under certain conditions (illness, stress, growth), some of them can become "conditionally essential".

Here are the non-essential amino acids:

• Alanine:The main transporter of nitrogen between tissues. Maintains blood glucose levels through participation in gluconeogenesis.

• Asparagine:Participates in the synthesis of other amino acids and is important for the proper functioning of the nervous system.

• Asparagic acid (Aspartate): Plays a role in the Krebs cycle, supports energy production, and participates in nerve impulse transmission.

• Glutamine: Conditionally essential. The most abundant amino acid in the blood. Key for immune function, digestive health, and recovery after physical exertion or illness.

• Glutamic acid (Glutamate):The main excitatory neurotransmitter in the CNS. Plays a role in learning and memory.

• Glycine: Component of collagen. Involved in detoxification, the synthesis of hemoglobin, and neurotransmitters.

• Proline: Main component of collagen – provides strength and elasticity to connective tissues, tendons, and skin.

• Serine: Involved in the synthesis of phospholipids, sphingolipids, and other amino acids. Also important for the proper function of the nervous system and brain.

• Tyrosine: Synthesized from phenylalanine. Precursor to catecholamines (dopamine, norepinephrine, adrenaline) and thyroid hormones.

• Cysteine (conditionally essential):Sulfur-containing amino acid, precursor to the antioxidant glutathione. Supports detoxification and protection against oxidative stress.

• Arginine (conditionally essential): Necessary for the synthesis of nitric oxide (NO), which regulates blood pressure and blood flow. Plays a role in immune function and wound healing.

• Ornithine(non-proteinogenic, non-protein amino acid): Involved in the urea cycle – detoxification of ammonia. Does not build proteins but plays an important role in metabolism.

The human body requires certain amounts of amino acids for normal growth, recovery, and maintenance of metabolic functions. The required amounts vary depending on age, sex, physical activity, and health condition.

Essential amino acids

Essential amino acids cannot be synthesized in the body and must be obtained through food.

The World Health Organization (WHO) recommends daily doses for adults, expressed in mg per kilogram of body weight:

• Leucine: 39 mg/kg

• Isoleucine: 20 mg/kg

• Lysine: 30 mg/kg

• Methionine + cysteine (sulfur-containing): 15 mg/kg

• Phenylalanine + tyrosine (aromatic): 25 mg/kg

• Threonine: 15 mg/kg

• Tryptophan: 4 mg/kg

• Valine: 26 mg/kg

• Histidine (semi-essential): 10 mg/kg

Non-essential amino acids

These are synthesized in the body, but under certain conditions (illness, stress, physical activity), additional intake from food or amino acid supplements may be required. Specific recommendations have not been established, as the body produces them in sufficient quantities under normal conditions.

Summary table of recommended daily doses for essential amino acids (for adults)

These quantities are approximate and may vary depending on specific needs such as pregnancy, breastfeeding, intense physical activity, or illnesses.

Amino acids are primarily obtained through food, with the richest sources being proteins from animal products – meat, fish, eggs, and dairy products. These are called complete sources because when animal proteins are broken down, our body obtains all the necessary essential amino acids.

Legumes, nuts, and seeds are rich in proteins but contain amino acids in smaller quantities and with an incomplete profile. For this reason, they are considered incomplete sources, as they are absorbed more slowly and do not provide all the essential amino acids in sufficient quantities.

To improve the amino acid profile of plant proteins, it is recommended to combine different foods. Examples of successful combinations include beans + rice, chickpeas + lentils, seeds + nuts, and others.

These combinations provide a more balanced amino acid composition, resembling that of complete animal sources.

In some cases, it may be necessary to take individual amino acids, complex amino acids, or proteins in the form of dietary supplements.

Additional amino acid intake is required during intense training, recovery after injuries or surgeries, age-related changes with reduced protein intake, specific diseases, and for vegetarians and vegans who may not get all the essential amino acids from their food.

What are amino acids?

Amino acids are a heterogeneous group of nitrogen-containing carbon organic compounds that perform many important functions in the human body and every other living organism.

What types of amino acids are mainly distinguished?

For the human body, the main types are essential (indispensable) – which must be obtained through food, and non-essential (replaceable) amino acids – which the body can synthesize on its own.

How to obtain amino acids?

The best sources of amino acids are of animal origin – eggs, milk, meat, while plant sources – like beans, soy, legumes, nuts, and seeds are incomplete and not sufficient to provide everything we need.