Proteins and amino acids
In a quantitative ratio among cellular biopolymers, the first place belongs to proteins. In an animal cell, they make up about 40-50% of dry weight, in a plant cage - 20-35%. The human body contains over 5 million types of protein molecules. Proteins include carbon, oxygen, hydrogen, sulfur. They may contain phosphorus, iron and some other chemical elements. Proteins are high molecular weight substances, heteropolymers, the monomers of which are amino acids.
Amino acids
The main role of amino acids is related to the fact that proteins are formed from them. In addition, they perform some specific functions in the body. For example, in the thyroid gland of vertebrates, the hormone thyroxine is formed from the amino acid tyrosine.
The variety of proteins is provided by combinations of 20 amino acids (the number of possible variants is about 2 x 10 18). The composition of amino acids includes carboxyl groups - (- COOH) with acidic properties and amino groups - (- NH 2), which are characterized by alkaline properties, therefore they are amphoteric connections. This predetermines their ability to interact. Carboxyl and amino groups are linked to the same carbon atom. Amino acids differ among themselves by side chains — radicals, R-groups. For different amino acids, they are not the same in chemical structure, electric charge, and solubility in water. The radicals of many amino acids contain polar groups; therefore, most amino acids are soluble in water.
Almost all amino acids of proteins belong to the same type of stereoisomers L-row , that is, the plane of the polarized light is reversed to the left. Found in microorganisms D-amino acids, which turn the plane of polarized light to the right.
To distinguish twenty amino acids from other amino acids also found in organisms, but not in proteins, they are called basic. Based on the possibility of synthesis in organisms, 20 amino acids are divided into replaceable and irreplaceable ... Essential amino acids are synthesized in the human and animal body. Essential amino acids are synthesized by plants, fungi, bacteria and enter the body with food.
Essential amino acids
| Essential amino acids | Abbreviations | Essential amino acids | Abbreviations |
| Alanin | Ala | Arginine | Arg |
| Asparagine | Asn | Valine | Shaft |
| Aspartic acid | Asp | Isoleucine | Ile |
| Histidine | Gis | Leucine | Leev |
| Glycine | Gley | Lysine | Lez |
| Glutamine | Gln | Methionine | Met |
| Glutamic acid | Glu | Threonine | Rub |
| Proline | About | Tryptophan | Three |
| Serine | Ser | Phenylalanine | Hair dryer |
| Tyrosine | Shooting gallery | ||
| Cysteine | Cis |
The composition of nonessential and essential amino acids changes with age. For example, in children, alanine and histidine are also indispensable, in addition to these.
Amino acids are conventionally represented by three letters for shorthand recording of their sequence in polypeptide chains.
There are additional amino acids besides the basic ones. They are components of only certain types of proteins, and each of them is a derivative of one of the 20 basic amino acids. For example, in one of the proteins that are responsible for blood clotting, prothrombin, a derivative of glutamic acid is found, etc.
Amino acids are complex organic substances consisting of a hydrocarbon radical, which may include sulfur or phosphorus, and two functional groups —NH 2 and —COOH. Nonessential and irreplaceable amino acids are isolated on the basis of this feature.
Amino acids
Amino acids are monomers composed of hydrocarbon, nitrogen and oxygen. Some compounds contain sulfur, phosphorus and some other elements. These are derivatives of carboxylic acids with the -COOH group. One amino acid can contain several amino groups.
Figure: 1. The structure of amino acids.
Amino acids are crystalline compounds that are soluble in water. They exhibit amphoteric properties and can react with inorganic substances - oxygen, water, acids, alkalis.
Amino acids form polymers - proteins that can be composed of various monomers. For example, casein includes tyrosine, lysine, valine, proline, and other amino acids.
Replaceable and irreplaceable
In total, about 500 amino acids are known. Amino acids are classified according to different characteristics depending on their structure, composition, physical properties. Of the total number of amino acids, only 22 are used by the body for the synthesis of primarily various proteins. Amino acids important for the body are classified into three groups:
- replaceable- are synthesized inside the body;
- irreplaceable- are not synthesized in the body;
- partially replaceable - are not synthesized in the body in large quantities.
Figure: 2. Classification of amino acids.
Replaceable amino acids are formed from substances that enter the body along with food. Irreplaceable ones cannot be formed in the body, therefore they come to the cells ready-made. Their absence leads to a decrease in mental activity, memory, immunity. Partially nonessential or partially essential amino acids are synthesized in the body, but most of them enter the body ready-made along with food.
The table of nonessential and essential amino acids lists substances with molecular formulas.
|
Replaceable |
Formula |
Irreplaceable |
Formula |
Partially replaceable |
Formula |
|
Asparagine |
Isoleucine |
||||
|
Histidine |
|||||
|
Carnitine |
Phenylalanine |
C 6 H 14 N 4 O 2 |
|||
|
C 5 H 12 N 2 O 2 |
Tryptophan |
C 11 H 12 N 2 O 2 |
|||
|
C 6 H 14 N 2 O 2 |
|||||
|
Methionine |
|||||
|
Glutamine |
C 5 H 10 N 2 O 3 |
||||
|
Glutamic acid |
Essential acids are found in legumes, rice, red and white meat, fish, eggs, and dairy products. With a balanced diet, a person receives all the necessary amino acids.
All amino acids can be divided into two categories: essential and non-essential. The name speaks for itself. Indispensable (essential) amino acids are an "irreplaceable" component of the diet. In other words, our body cannot synthesize them on its own. Nonessential amino acids are those that can be metabolized from other amino acids and nutrients in the diet.
Nonessential amino acids include:
- Asparagine
- Glutamic acid
- Glycine
- Proline
- Serine
Essential amino acids cannot be synthesized by the body, and therefore, in their absence in food, the body begins to use reserve reserves of amino acids, for example, albumin. In the worst case, the need for amino acids is replenished by muscle tissue - a process that is highly undesirable for all bodybuilders and other sportsmen.
Essential amino acids:
- Histidine
Essential amino acids
Histidine
Histidine is present in all tissues of the human body. It plays an important role in the formation of red and white blood cells and takes part in the exchange of information between the central nervous system and peripheral tissues. The immune system needs histidine to prevent autoimmune and allergic reactions, and in the stomach, with the participation of this amino acid, gastric juice is formed, which is necessary for normal digestion. Histidine deficiency contributes to the development of rheumatoid arthritis. The reserves of histidine in our body are depleted quite quickly, and therefore we must regularly receive it from external sources.
Histidine is found in meat, dairy products, grains (wheat, rice, rye).
Application: improving digestion. Sources: dairy products, meat, fish, rice, wheat, rye.
One of the main bodybuilding amino acids, as isoleucine is one of the three amino acids. Isoleucine helps increase physical endurance and accelerates muscle recovery, stimulates post-workout recovery and supports continuous energy replenishment.
Good sources of isoleucine include meats, eggs, fish, nuts, seeds, peas, and soy.
Promotes muscle recovery. Sources: Chicken, cashews, fish, almonds, eggs, lentils, liver and meat.
The second amino acid from the BCAA class, which, along with isoleucine and valine, plays an important role in the recovery of muscle tissue. Leucine converts more efficiently and faster than other amino acids into glucose, thereby stopping catabolic processes in the muscles during grueling training sessions. It is also involved in muscle recovery after microdamage, regulates blood sugar levels, increases the secretion of growth hormone and promotes fat burning.
Sources of Leucine: Brown rice, beans, meat, nuts, soy flour, and whole wheat.
Application: natural anabolic agent. Sources: All protein sources, including brown rice, legumes, nuts, and whole wheat.
This amino acid is known for its antiviral properties. With the participation of lysine, antibodies are synthesized that strengthen the immune system; lysine is also needed for the formation of hormones that regulate the processes of growth and renewal of bone tissue. Due to its antiviral properties, lysine helps to treat and / or prevent colds and herpes infections. Also, this amino acid stimulates the production of collagen and muscle protein, which leads to an early recovery.
Good sources of lysine include red meat, cheese, eggs, fish, milk, potatoes, and yeast.
Application: fights fatigue and overtraining. Sources: cheese, eggs, milk, meat, yeast, potatoes and beans.
Helps recycle and utilize fats. Takes part in the formation of glutathione, cysteine \u200b\u200band, contributing to the neutralization and elimination of toxic substances from the body. Methionine is needed for the synthesis of creatine, a substance that increases the endurance and performance of skeletal muscles. Essential for collagen synthesis for healthy looking skin and nails. For people with allergies or arthritis, taking this amino acid can help lower histamine levels in the body.
Sources of Methionine: Meat, eggs, fish, garlic, beans, lentils, onions, soy, seeds, and yogurt.
Application: metabolism. Sources: Meat, fish, legumes, eggs, garlic, lentils, onions, yogurt, and seeds.
An essential amino acid necessary for the normal functioning of the central nervous system. Since phenylalanine easily penetrates the blood-brain barrier, it is successfully used to treat neurological diseases. This amino acid also helps control symptoms of depression and chronic pain. Research has shown that phenylalanine can also help treat vitiligo (white patches of discoloration on the skin). Taking phenylalanine can improve memory and concentration, as well as improve mood and emotional background. This amino acid is used in the treatment of Parkinson's disease and schizophrenia, but anyone who wants to take phenylalanine as a dietary supplement should consult a doctor first. People with hypertension and / or migraine, as well as phenylketonuria, should avoid this amino acid and foods containing it in large quantities. High doses of phenylalanine can damage nerve tissue.
Application: promotes maximum muscle contraction and relaxation. Sources: Dairy, almonds, avocados, nuts, and seeds.
Vital for the formation of muscle tissue, collagen and elastin, participates in the creation of strong bones and teeth (enamel). Stimulates growth processes and normalizes protein metabolism in the body. Supports almost all body systems: central nervous, cardiovascular and immune. Prevents fatty degeneration of the liver.
With a healthy, balanced diet, threonine deficiency is unlikely as it is present in dairy products, meats, grains, mushrooms, and green vegetables.
Application: normalizes protein metabolism. Sources: meat, dairy products and eggs.
Tryptophan
Can be converted to niacin. Used in the synthesis of methionine and serotonin. Serotonin helps regulate blood pressure and respiratory function. An increase in the amount of serotonin in the body leads to calming and better sleep.
One of the branched chain amino acids (BCAAs). Along with other BCAAs, it promotes normal tissue growth and repair. Provides the body with energy, thereby preventing the breakdown of muscle tissue, regulates the level of glycemia. Valine is necessary for normal mental activity, participates in the excretion of excess nitrogenous compounds by the liver, and, if necessary, can be transported to other organs and tissues. Valine can help treat liver and brain damage from alcohol, drug, or drug abuse. This amino acid should be taken in combination with other BCAAs: leucine and isoleucine.
Natural sources of valine: meat, dairy products, mushrooms, peanuts, soy protein.
Application: promotes the recovery and growth of muscle tissue. Sources: dairy products, meat, mushrooms, soybeans, peanuts.
Essential amino acids
Alanin
It is used as a source of energy, accelerating the conversion of glucose during energy metabolism, and also helps to eliminate toxins from the liver. Prevents the breakdown of muscle tissue due to the so-called alanine cycle, which can be simplified as follows: glucose - pyruvate - alanine - pyruvate - glucose. The alanine cycle increases intracellular energy stores and thus prolongs cell life. During this cycle, excess nitrogen is removed from the body (urination). Alanine can relieve symptoms caused by an enlarged prostate.
Sources of alanine include meat, poultry, eggs, dairy products, fish, and some plant foods such as avocados.
One of the essential amino acids in the human body that is essential for maintaining healthy joints, liver, skin and muscles. Due to its regenerative properties, it can be used by people suffering from arthritis and other joint diseases. Strengthens the immune system by increasing the production of T-lymphocytes. Participates in the synthesis of creatine and in nitrogen metabolism, which is of enormous importance for every bodybuilder. It also helps to reduce the proportion of adipose tissue in the body and accelerates the healing of damaged tissues. Although arginine is produced in the body, taking the amino acid with dietary supplements should be considered for people suffering from infection or burns, as well as people looking to lose weight, strengthen the immune system, or gain muscle mass.
Natural Sources of Arginine: Meat, Dairy, Wheat, Chocolate, Coconut, Gelatin, Oats, Peanuts, Soy, and Walnuts.
Application: helps to increase muscle mass and reduce fat accumulation. Sources: Whole wheat, nuts, seeds, rice, chocolate, raisins, and soy.
Asparagine
Closely related to aspartic acid, it is necessary for the functioning of the nervous system, in addition, our body uses this amino acid to synthesize ammonia.
Asparagine can be found in animal and plant foods: beef, poultry, whey, eggs, fish, dairy products, asparagus, potatoes, nuts, seeds, and whole grains.
Aspartic acid, also known as L-aspartate
Promotes the improvement of metabolic processes and takes part in the synthesis of other amino acids, in particular, arginine, lysine and isoleucine. Aspartic acid is of great importance for the synthesis of cellular energy, since it takes part in the formation of adenosine triphosphate (ATP) - a universal fuel that provides energy for all intracellular processes. Supports the nervous system by increasing the concentration of nicotinamide adenine dinucleotide (NADH), a substance that stimulates the production of neurotransmitters and other compounds necessary for the normal functioning of the brain.
Aspartic acid can be synthesized in the body, and its sources include poultry, dairy products, beef and sugar cane.
Contained in beta-keratin - the main structural protein of skin, nails and hair. Cysteine \u200b\u200bis best absorbed in the form of N-acetyl cysteine \u200b\u200b(NAC). Cysteine \u200b\u200bmay be effective in treating cancer, bronchitis, smoker's cough, cardiac disease, and septic shock.
This amino acid is produced in the body, but it can also be obtained from meat, eggs, broccoli, onions, garlic and red peppers.
Application: promotes faster recovery and maintaining good physical shape. Sources: Poultry, wheat, broccoli, eggs, garlic, onions and peppers.
Glutamic acid, also known as glutamate
The most important excitatory neurotransmitter of the brain and spinal cord. Plays a key role in the metabolism of fats and carbohydrates, participates in the transport of potassium to the cerebrospinal fluid and across the blood-brain barrier. The brain can use glutamic acid as fuel. Can be converted to glutamine or GABA (gamma-aminobutyric acid).
Helps build and maintain muscle and remove toxins from the liver. Can penetrate the blood-brain barrier and, once converted to glutamic acid, act as brain fuel. May also increase GABA levels. Glutamine is an essential source of energy for the nervous system. L-glutamine preparations are used mainly in bodybuilding, however, while taking glutamine, people also notice a general surge of strength and an improvement in the emotional background. Glutamine is formed by amination (attachment of the amino group) of glutamic acid, which helps to remove toxic ammonia from the liver - nitrogen does not convert to ammonia.
Glutamine also helps transport nitrogen to other organs and tissues, especially muscles, where it helps to increase glycogen stores. This is of great importance in preventing muscle breakdown. Up to 60% of the amino acids found in muscles are glutamine. Glutamine is also important for the immune system and may help treat rheumatoid arthritis, chronic fatigue, and scleroderma.
Glutamine is found in many foods, but it breaks down quickly during cooking. Raw parsley and spinach are excellent sources of this amino acid.
Application: An additional source of energy during the diet. Sources: High in all protein foods.
Glycine
This amino acid helps build muscle tissue, is involved in converting glucose into energy, and increases creatine levels to help build muscle. Collagen is approximately 30% glycine. In fact, without this amino acid, the body cannot heal wounds and other tissue damage.
High protein foods such as fish, meat, milk, beans, or cheese are excellent sources of glycine.
Proline
Proline is needed for the formation of collagen and cartilage tissue. It stimulates collagen synthesis, which in turn promotes cartilage remodeling, and therefore may be beneficial for people suffering from injuries and joint diseases. This amino acid speeds up the healing process and is successfully used during the recovery period from injuries, for example, after burns.
Good sources of proline are meat, dairy products, and eggs. Vegetarians should consider taking this amino acid with dietary supplements.
Serine
Serine's main function is to maintain the normal functioning of the brain and central nervous system. Proteins of the nervous tissue and its protective cells contain this amino acid. She is also involved in the synthesis of serotonin, a chemical compound that has a significant effect on mood. In addition, serine is involved in the metabolism of fats and fatty acids and promotes the absorption of creatine.
Meat, dairy, wheat (gluten), soy, and peanuts are examples of good sources of this amino acid.
Tyrosine
This amino acid contributes to the normal functioning of the entire body. Tyrosine helps control appetite, and its deficiency is fraught with a decrease in blood pressure, a slowdown in metabolic processes and increased fatigue. In addition, tyrosine promotes the formation of neurotransmitters, which has a great influence on the interaction of the human body with the environment.
Conclusion
Amino acids are essential for the body to function. Supplements can be helpful, but sometimes they lead to side effects, so be sure to consult with a qualified professional before taking amino acid preparations. This is very important, since hidden health problems can be exacerbated by the intake of amino acids. In addition, some of these amino acids are produced in the body, and many amino acids come from food, and therefore it is important to determine whether additional influx of these nutrients is really necessary. It should be noted that amino acids are sold over the counter and are generally considered safe.
Organic matter. The concept of biopolymers. As already noted, the composition of living organisms, in addition to inorganic ones, includes various organic substances: proteins, lipids, carbohydrates, nucleic acids, etc. They are formed, first of all, by four chemical elements: carbon, hydrogen, oxygen and nitrogen. In the composition of proteins, sulfur is added to these elements, and in nucleic acids, phosphorus.
In living organisms, organic matter is represented by both small molecules with a relatively low molecular weight and macromolecules. TO low molecular weightcompounds include amino acids, monosaccharides, nucleotides, carboxylic acids, alcohols and some others. Macromolecules(from the Greek. macro - large) are represented by proteins, polysaccharides and nucleic acids. These are compounds with a complex structure with a large molecular weight. Thus, the relative molecular weight of most proteins ranges from 5,000 to 1,000,000. As you know from the course of chemistry, the relative molecular weight (L4 G) is equal to the ratio of the mass of one molecule of a substance to a fraction of the mass of a carbon atom and, therefore, is a dimensionless quantity. The A4 G value shows how many times the mass of a molecule of a given substance is greater than an atomic mass unit.
Molecules of proteins, polysaccharides and nucleic acids consist of a large number of repeating units of the same or different composition. As you know from the chemistry course, such compounds are called polymers.Simple molecules, of the residues of which polymers are composed, are called monomers.Monomers of proteins are amino acids, monomers of polysaccharides are monosaccharides, nucleic acid molecules are built from nucleotides. Proteins, polysaccharides and nucleic acids are found in the cells of all living organisms and perform extremely important biological functions, therefore they are called biological polymers (biopolymers).
In the cells of various living organisms, the content of certain organic compounds is different. For example, proteins and lipids predominate in animal cells, and carbohydrates in plant cells. However, in different cells, certain organic compounds perform similar functions.
In living organisms, proteins play the leading role among macromolecules in terms of their functional significance. Proteins in many organisms also predominate quantitatively. So, in the organism of animals they make up 40-50%, in the organism of plants - 20-35% of dry mass. Proteins are polymers whose monomers are amino acids.
Amino acids — "Building blocks" of protein molecules. Amino acids are organic compounds containing both an amino group (—NH 2), which is characterized by basic properties, and a carboxyl group (—COOH) with acidic properties. About 200 amino acids are known, but only 20 are involved in the formation of natural proteins. Such amino acids are called protein-forming. Table 2 shows the full and abbreviated names of these amino acids (not for memorization).
Table 2. Protein-forming amino acids and their abbreviations
|
Amino acid name |
Designation |
Amino acid name |
Designation |
|
Asparagine |
Methionine |
||
|
Aspartic acid |
|||
|
Histidine |
|||
|
Glutamine |
Tryptophan |
||
|
Glutamic acid |
Phenylalanine |
||
|
Isoleucine |
In the molecules of protein-forming amino acids, the carboxyl group and the amino group are linked to the same carbon atom. On this basis, 20 amino acids are similar to each other. Another part of the molecule, called the radical (R), has a different structure for different amino acids (Fig. 6). The radical can be non-polar or polar, hydrophobic or hydrophilic, which gives different amino acids special properties.
Most of the protein-forming amino acids have one carboxyl group and one amino group - these amino acids are called neutral (see Fig. 6). There are also basic amino acids, with more than one amino group, and acidic amino acids, with more than one carboxyl group. The presence of an additional amino or carboxyl group affects the properties of the amino acid, which play a decisive role in the formation of the spatial structure of the protein. The radical of some amino acids (for example, cysteine) contains sulfur atoms.
Autotrophic organisms synthesize all the amino acids they need from the primary products of photosynthesis and nitrogen-containing inorganic compounds. For heterotrophic organisms, food is the source of amino acids. In humans and animals, some amino acids can be synthesized from metabolic products (primarily from other amino acids). These amino acids are called nonessential. Others, the so-called essential amino acids, cannot be synthesized in the body and therefore must constantly enter it as part of food proteins. Food proteins containing residues of all essential amino acids are called complete, in contrast to defective ones, which do not contain residues of certain essential amino acids.
Indispensable amino acids for humans are: tryptophan, lysine, valine, isoleucine, threonine, phenylalanine, methionine and leucine. Arginine and histidine are also indispensable for children.
The presence of both basic and acidic groups determines the amphotericity and high reactivity of amino acids. The amino group (—NH 2) of one amino acid is capable of interacting with the carboxyl group (—COOH) of another amino acid. In this case, a water molecule is released, and a covalent bond appears between the nitrogen atom of the amino group and the carbon atom of the carboxyl group, which is called peptide bond.The resulting molecule is dipeptide(fig. 7). There is a free amino group at one end of the dipeptide molecule, and a free carboxyl group at the other. Thanks to this, the dipeptide can bind other amino acids to itself, forming oligopeptides.If more than 10 amino acid residues, then polypeptide.
Peptides play an important role in the human body. Many hormones (glucagon, vasopressin, o x and tots and others), antibiotics (for example, gramicidin), toxins (for example, diphtheria toxin) are oligo- and polypeptides by chemical nature.
Proteins. The levels of organization of a protein molecule. Polypeptide chains can be very long and include a wide variety of combinations of amino acid residues. Polypeptides, whose molecules contain from 50 to several thousand amino acid residues, are called proteins.Each specific protein is characterized by a strictly constant composition and sequence of amino acid residues.
Proteins formed only by amino acid residues are called simple proteins. Complex proteins are proteins that have a non-amino acid component in their composition. These can be metal ions (Fe 2+, Zn 2+, Mg 2 ^ Mn 2+), lipids, nucleotides, sugars, etc. Simple proteins are blood albumin, fibrin, some enzymes (trypsin), etc. Complex proteins are most enzymes are immunoglobulins (antibodies).
Protein molecules can take different spatial forms, which represent four levels of their structural organization (Fig. 8).
A chain of many amino acid residues connected by peptide bonds is primary structureprotein molecule. It is the most important structure as it determines the shape, properties and function of the protein. Other types of structures are created based on the primary structure. Each protein in the body has a unique primary structure.
Secondary structureprotein arises as a result of the formation of hydrogen bonds between the hydrogen atoms of the NH-groups and the oxygen atoms of the CO-groups of different amino acid residues of the polypeptide chain. In this case, the polypeptide chain is twisted into a spiral. Hydrogen bonds are weak, but due to their significant amount, they ensure the stability of this structure. For example, keratin molecules, the main protein of human hair and nails, have a completely spiral configuration. A helical secondary structure is characteristic of some other proteins, for example, for myosin
The secondary structure of the protein, in addition to the helix, can be represented by a folded layer. In this case, several polypeptide chains (or sections of one polypeptide chain) are arranged in parallel, forming a structure folded like an accordion (see Fig. 8). This configuration has, for example, the protein fibroin, which is the basis of natural silk fibers.
Tertiary structureis formed due to the formation of hydrogen, ionic and other bonds that arise between different groups of atoms of a protein molecule in an aqueous medium. In some proteins, S - S bonds (disulfide bonds) between cysteine \u200b\u200bresidues (an amino acid containing sulfur) play an important role in the formation of the tertiary structure. In this case, the polypeptide helix folds into a kind of coil (globule) in such a way that hydrophobic amino acid radicals are immersed inside the globule, and hydrophilic ones are located on the surface and interact with water molecules. The tertiary structure determines the specificity of protein molecules, their biological activity. Many proteins have a tertiary structure, such as myoglobin (a protein that is involved in creating oxygen in muscles) and trypsin (an enzyme that breaks down food proteins in the intestine).
The molecules of some proteins include not one, but several polypeptides that form a single complex. This is how quaternary structure.Polypeptides (they can have the same or different structure) are not bound by covalent bonds. The strength of the quaternary structure is provided by the interaction of weak intermolecular forces. For example, a quaternary structure is characteristic of the hemoglobin protein. Its molecule consists of four structural elements - subunits, each subunit includes a polypeptide chain and a non-protein component - heme.
1. What substances are biological polymers? What substances are monomers for building biopolymer molecules?
a) Amino acids; d) nucleotides;
b) nucleic acids; e) proteins;
c) polysaccharides; f) monosaccharides.
2. What functional groups are characteristic of all amino acids? What properties do these groups possess?
3. How many amino acids are involved in the formation of natural proteins? What are the common structural features of these amino acids? How do they differ?
4. How are amino acids linked to form a polypeptide chain? Build dipeptide and tripeptide. To complete the task, use the structural formulas of amino acids shown in Figure 6.
5. Describe the levels of the structural organization of proteins. What chemical bonds cause different levels of structural organization of protein molecules?
6. Humans and animals get amino acids from food. What can amino acids be synthesized in plants?
7. How many different tripeptides can be built from three amino acid molecules (eg, alanine, lysine and glutamic acid) if each amino acid can only be used once? Will these peptides have the same properties?
8. To separate a mixture of proteins into components, the method of electrophoresis is used: in an electric field, individual protein molecules move at a certain speed to one of the electrodes. In this case, some proteins move towards the cathode, others move towards the anode. How is the structure of a protein molecule related to its ability to move in an electric field? What determines the direction of movement of protein molecules? What determines their speed?
- § 1. The content of chemical elements in the body. Macro and microelements
- § 2. Chemical compounds in living organisms. Inorganic substances
- § 10. History of the discovery of the cell. Creation of cell theory
- § 15. Endoplasmic reticulum. Golgi complex. Lysosomes
Chapter 1. Chemical components of living organisms
Chapter 2. Cell - structural and functional unit of living organisms
Chapter 3. Metabolism and energy conversion in the body
AMINO ACIDS
Low molecular weight organic compounds containing one or two carboxyl groups (—COOH) and one or two amino groups (—NH2). Amino acids are widely found in cells and tissues of living organisms. General formula of the most important natural amino acids
where the R radical can be hydrogen (as in the case of the simplest amino acid glycine), a methyl group - CH3 (as in alanine), or have a more complex structure.
Since amino acids are amphoteric, that is, they have the properties of both acids and bases, they react with each other. The carbon atom of the carboxyl group of one amino acid combines with the nitrogen atom of the amino group of the other to form the so-called. peptide bond, while water is split off.
If two amino acids are combined, a dipeptide is formed, if three - a tripeptide, if 20 or more amino acids - a polypeptide (see peptides). In living organisms, approx. 150 amino acids, but only 20 of them are involved in the construction of protein polypeptide chains - translation. The sequence of amino acids in the synthesized polypeptide chain is determined by the genetic code.
Of the 20 amino acids necessary for the construction of proteins in the body of animals and humans, only the so-called. nonessential amino acids. The rest - essential amino acids - must come from food. The set of essential amino acids is different for different animals. For humans, these are 8 amino acids - valine, leucine, lysine, methionine, etc. The absence or deficiency of one or more essential amino acids in the human body leads to metabolic disorders and various diseases. Plants and chemosynthetic microorganisms synthesize all essential amino acids themselves.
In addition to building proteins, amino acids (including those not included in proteins) serve as starting materials for the synthesis of vitamins, nitrogenous bases, mediators and other biologically active compounds in cells.
Amino acids are used in medicine, as food additives, for fortification of feed and for other purposes. On an industrial scale, they are obtained by microbiological synthesis (see biotechnology).
When studying the possible pathways for the origin of life, a number of amino acids were obtained by passing electrical discharges through a mixture of gases that recreate the primary atmosphere of the Earth. Thus, the possibility of abiogenic (without the participation of organisms) synthesis of the most important organic compounds was shown.
Encyclopedia Biology. 2012
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(syn. aminocarboxylic acids) organic (carboxylic) acids containing one or more amino groups; are the main structural units of protein molecules, determine their biological ... - AMINO ACIDS in the Big Encyclopedic Dictionary:
- AMINO ACIDS in the Great Soviet Encyclopedia, TSB:
a class of organic compounds that combine the properties of acids and amines, that is, they contain, along with the carboxyl group -COOH, the amino group -NH2. ... - AMINO ACIDS in the Encyclopedic Dictionary of Brockhaus and Euphron:
the name recently used in some manuals of organic chemistry instead of the name "amido acids", which is more correct, because in these compounds ... - AMINO ACIDS in the Modern Encyclopedic Dictionary:
- AMINO ACIDS in the Encyclopedic Dictionary:
a class of organic compounds containing carboxyl (- COOH) and amino groups (- NH2) have the properties of both acids and bases. Participate in the exchange ... - AMINO ACIDS in the Encyclopedic Dictionary:
, -from, units. amino acid, s, g. (specialist.). A class of organic compounds with properties of both acids and bases. II app. amino acid, th, ... - AMINO ACIDS in the Big Russian Encyclopedic Dictionary:
AMINO ACIDS, organic class comp. containing carboxyl (-COOH) and amino groups (-NH 2); possess the properties of both acids and bases. Participate in ... - AMINO ACIDS in the Encyclopedia of Brockhaus and Efron:
? the name used recently in some manuals of organic chemistry instead of the name "amido acid", which is more correct, because in these ... - AMINO ACIDS in the New Dictionary of Foreign Words:
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a class of organic compounds that are characterized by the properties of both carboxylic acids and amines; and. play a big role in the life of organisms, ... - AMINO ACIDS in the New Explanatory Dictionary of the Russian Language by Efremova:
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amino acids, - from, units. -ta, ... - AMINO ACIDS in the Spelling Dictionary:
amino acids, - from, units. -a, ... - AMINO ACIDS in the Ozhegov Russian Language Dictionary:
a class of organic compounds with properties and acids, and ... - AMINO ACIDS in the Modern Explanatory Dictionary, TSB:
a class of organic compounds containing carboxyl (-COOH) and amino groups (-NH2); possess the properties of both acids and bases. Participate in the exchange of nitrogenous substances ... - AMINO ACIDS in the Explanatory Dictionary of Efremova:
amino acids pl. Organic compounds with the properties of acids and alkalis and are the main element of plants and animals ... - AMINO ACIDS in the New Dictionary of the Russian Language by Efremova:
pl. Organic compounds with the properties of acids and alkalis and are the main element of plants and animals ... - AMINO ACIDS in the Big Modern Explanatory Dictionary of the Russian Language:
pl. Organic compounds with the properties of acids and alkalis and are the main element of plants and animals ... - Broadcast in Encyclopedia Biology:
, synthesis of proteins (polypeptides) on ribosomes using informational ribonucleic acid (i-RNA) as a matrix; the final stage of implementation ...