The importance of hydrogen bonding in biology. Hydrogen bond. Importance of intermolecular hydrogen bond

Hydrogen is an element of group VII periodic table with atomic number 1. First isolated by the Flemish chemist I. Van Helmont in the 17th century. Studied by the English physicist and chemist G. Cavendish at the end of the 18th century. The name hydrogen comes from the Greek. hydro genes (generating water).

Hydrogen is one of the most abundant elements in the Universe. The energy emitted by the Sun is generated as a result of the fusion of four hydrogen nuclei into a helium nucleus. On Earth, hydrogen is found in water, minerals, coal, oil, and living things. Small amounts of hydrogen are found in free form in volcanic gases.

Hydrogen is a colorless and odorless gas, does not dissolve in water, and forms explosive mixtures with air. There are three varieties of hydrogen: protium, deuterium and tritium, differing in the number of neutrons. Hydrogen is produced by electrolysis of water, as a by-product during oil refining.

• Biological role of hydrogen

  The role of hydrogen in nature is determined not by mass, but by the number of atoms, the share of which among other elements is 17% (second place after oxygen, the share of atoms of which is ~ 52%). Therefore, the value of hydrogen in chemical processes occurring on Earth is almost as great as oxygen. Unlike oxygen, which exists on Earth in both bound and free states, almost all hydrogen on Earth is in the form of compounds. Only in very small quantities is hydrogen in the form simple substance contained in the atmosphere (0.00005% by volume).

  The main function of hydrogen is the structuring of biological space (water and hydrogen bonds) and the formation of a variety of organic (biological) molecules. Hydrogen is capable of reacting with electron-positive and electron-negative atoms, actively interacting with many elements, exhibiting both oxidative and restorative properties. In reactions with alkali and alkaline earth metals, hydrogen acts as an oxidizing agent, and in relation to oxygen, sulfur, and halogens it exhibits reducing properties.

  When an electron is lost, a hydrogen atom becomes elementary particle- proton. In an aqueous solution, the proton transforms into a hydronium cation, which is hydrated by three water molecules and forms the hydrated hydronium cation H 9 O 4+. In the form of this cation, protons are found in an aqueous solution.

  In biological processes, the proton plays an extremely important role: it determines acid properties solutions, participates in redox transformations. With the participation of hydrogen ions, metal cations are bound into biocomplexes, precipitation reactions occur (for example, the formation of the mineral basis of bone tissue), hydrolytic decomposition of lipids, polysaccharides, and peptides.

  In the human body, hydrogen, in combination with other macroelements, forms amino groups and sulfhydryl groups, which play a critical role in the functioning of various biomolecules. Hydrogen is included in the structure of proteins, carbohydrates, fats, enzymes and other bioorganic compounds that perform structural and regulatory functions. Thanks to hydrogen bonds, the DNA molecule is copied, which transmits genetic information from generation to generation.

  When hydrogen reacts with oxygen, it forms a water molecule. Water is the main substance that makes up the body. In the body of a newborn human, the water content is about 80%, in an adult it is 55-60%. Water takes part in a huge number of biochemical reactions, in all physiological and biological processes, ensures the exchange of substances between the body and the external environment, between cells and within cells. Water is the structural basis of cells; it is necessary for them to maintain their optimal volume; it determines the spatial structure and functions of biomolecules.

  In biological media, part of the water (about 40%) is in a bound state (associates with inorganic ions and biomolecules). The rest, i.e. free water is a mobile structure associated with hydrogen bonds. There is a continuous exchange of molecules between free and bound water.

  Water in the body is conventionally divided into extracellular and intracellular. Extracellular water, in turn, is the interstitial fluid surrounding cells; intravascular fluid (blood plasma) and transcellular fluid, which is found in serous cavities and hollow organs. The accumulation of water in the body (hyperhydration) may be accompanied by an increase in water content in the intercellular sector (edema), in the serous cavities (dropsy) and inside cells (swelling). A decrease in water content in the body (dehydration) is accompanied by a decrease in turgor, dry skin and mucous membranes, hemoconcentration and hypotension.

  There is a theory related to the structured nature of water, about the so-called informational role of water in living systems and the presence of aqueous solutions structural memory.

  Despite the fact that water is one of the main components human body, its role is still underestimated and little studied by both scientists and representatives of practical medicine. Meanwhile, a person’s loss of almost all glycogen and fat or half of their protein has less health consequences than the loss of just 10% of water (while the loss of 20% of water is fatal).

  A person’s need for water is 1-1.5 ml per kcal of food consumed, i.e., with an energy value of the diet of 2000 kcal, the body requires 2 to 3 liters of water per day. About 300-400 ml of water is formed daily in the human body as a result of various metabolic reactions. Oxidation of 1 g of carbohydrates leads to the formation of 0.6 g of water, 1.07 g of lipids and 0.41 g of proteins.

• Hydrogen toxicity

  Hydrogen is non-toxic. The lethal dose for humans has not been determined.

• Applications of hydrogen compounds

  Hydrogen compounds are used in the chemical industry to produce methanol, ammonia, etc.

  In medicine, one of the hydrogen isotopes (deuterium) is used as a label in pharmacokinetic studies medicines. Another isotope (tritium) is used in radioisotope diagnostics, in the study of biochemical reactions of enzyme metabolism, etc.

  Hydrogen peroxide H 2 O 2 is a means of disinfection and sterilization.

Hydrogen bonds are a specific bond that is created by the H atom, which is found in the groups OH, NH, FH, ClH and sometimes SH, and H bonds these groups with the valence-saturated atoms N2, O2 and F.

Hydrogen bonds determine the structure and properties of water, as the most important and basic solvent in biological systems. Hydrogen bonds are involved in the formation of macromolecules, biopolymers, as well as bonds with small molecules.

Uwater = 4-29 kJ/mol

The main contribution to hydrogen bonds comes from electrostatic interactions, but they are not limited to them. A proton moves along a straight line connecting electronegative atoms and experiences different influences from these atoms.

This graph is a special case, the relationship between N-H...N and N...H-N. R is the distance between interacting particles. 2 free energy minima are located near the first or second interacting N atom.

• 
  Hydrogen communications–specific connection, which is created by the H atom, which is located in the groups OH, NH, FH, ClH and sometimes SH, and H binds these groups to the valence-saturated atoms N2, O2 and F.


• 
  Hydrogen connection And her role V biological systems. Hydrogen communications–specific connection, which is created by the H atom that is in the group.


• 
  Hydrogen connection And her role V biological systems.
  She built in the form of a network of protein fibrillar molecules, among which a significant role plays alpha actinin.


• 
  Hydrogen connection And her role V biological systems. Hydrogen communications–specific connection


• 
  Hydrogen connection And her role V biological systems. Hydrogen communications–specific connection, which is created by the H atom, which is in the OH groups, ... more ».


• 
  Hydrogen connection And her role V biological systems. Hydrogen communications–specific connection, which is created by the H atom, which is in the OH groups, ... more ».


• 
  Role V biological systems.
  hydrogen connection Chemical communications


• 
  2) intermolecular, if the EA and EV atoms are in different molecules. Intramolecular hydrogen communications play the most important biological role, since they determine, for example, the helical structure of polymeric protein molecules.


• 
  Shuttle transfer mechanisms hydrogen. home role CTK - education large quantity ATP.
  In this transport system hydrogen from cytoplasmic NAD is transferred to mitochondrial NAD, therefore 3 are formed in mitochondria ATP molecules And...


• 
  Role diffusion in substance transfer processes V biological systems.
  Intermolecular and intramolecular hydrogen connection Chemical communications in molecules there is usually a very pro... more ».

Similar pages found:10

3 What chemical bond is called a hydrogen bond? What are the features of hydrogen bonding? What can be said about the strength of hydrogen bonds compared to covalent and ionic ones? What is the significance of hydrogen bonding in chemistry and biology?

Hydrogen bonding is chemical bond between hydrogen atoms and atoms of strongly electronegative elements (fluorine, oxygen, nitrogen). A hydrogen bond is usually formed between two neighboring molecules. For example, it is formed between molecules of water, alcohols, hydrogen fluoride, and ammonia.

This is a very weak bond - about 15-20 times weaker than a covalent bond. Thanks to it, some low-molecular substances form associates, which leads to an increase in the melting and boiling points of substances.

Abnormally high temperatures melting and boiling are characteristic of water (if we consider hydrogen compounds VI group). All hydrogen compounds of group VI, except water, are gases.

1)orientation(polar molecules, due to the electrostatic interaction of the opposite ends of the dipoles, are oriented in space so that the negative ends of the dipoles of some molecules are turned to the positive ends of the dipoles of other molecules)

2)induction(also observed in substances with polar molecules, but it is usually much weaker than the orientational one. A polar molecule can increase the polarity of a neighboring molecule. In other words, under the influence of the dipole of one molecule, the dipole of another molecule can increase, and a non-polar molecule can become polar)

3)dispersive(these forces interact between any atoms and molecules, regardless of their structure. They are caused by instantaneous dipole moments that occur in concert in a large group of atoms)

35. Hydrogen bond, its biological role.

36. Complex compounds. Werner's theory. Role in a living organism.

37. Dissociation of complex compounds. Instability constant of complex ions.

38. Chemical bonding in complex compounds (examples).

In crystalline complex compounds with charged complexes the connection between the complex and outer-sphere ions ionic, connections between the remaining particles of the outer sphere – intermolecular(including hydrogen ones). In most complex particles there are bonds between the central atom and the ligands covalent. All of them or part of them are formed according to the donor-acceptor mechanism (as a consequence - with a change in formal charges). In the least stable complexes (for example, in aqua complexes of alkali and alkaline earth elements, as well as ammonium), the ligands are held by electrostatic attraction. Bonding in complex particles is often called donor-acceptor or coordination bonding.

39. Redox reactions. Types of redox reactions.

Types of redox reactions:

1) Intermolecular- reactions in which oxidizing and reducing atoms are found in molecules of different substances, for example:

H 2 S + Cl 2 → S + 2HCl

2) Intramolecular- reactions in which oxidizing and reducing atoms are found in molecules of the same substance, for example:

2H 2 O → 2H 2 + O 2

3) Disproportionation (auto-oxidation-self-healing) - reactions in which the same element acts both as an oxidizing agent and as a reducing agent, for example:

Cl 2 + H 2 O → HClO + HCl

4)Reproportionation- reactions in which one oxidation state is obtained from two different oxidation states of the same element, for example:

NH 4 NO 3 → N 2 O + 2H 2 O

40. The most important oxidizing agents and reducing agents. Redox duality.

One molecule and the hydrogen atoms of another, type N-X(X is F, O, N, Cl, Br, I) due to the forces of electrostatic attraction.

The bond between hydrogen and one of these atoms is characterized by sufficient polarity, since the binder electron cloud shifted towards the more electronegative atom. Hydrogen in this case is located at the positive end of the dipole. Two or more such dipoles interact with each other so that the nucleus of the hydrogen atom of one molecule (the positive end of the dipole) is attracted by the lone electron pair of the second molecule. This relationship manifests itself in gases, liquids and solids.

It is relatively durable. The presence of a hydrogen bond causes an increase in the stability of the molecules of a substance, as well as an increase in their boiling and melting points. The formation of hydrogen bonds plays an important role in both chemical and biological systems.

Hydrogen bonding can be intra- and intermolecular (Fig. 14), molecules carboxylic acids in nonpolar solvents they dimerize due to two intermolecular hydrogen bonds.

Rice. 14. Formation of hydrogen bond: A- intramolecular; b- intermolecular.

The existence of substances in different states of aggregation indicates that there is interaction between particles (atoms, ions, molecules) due to van der Waals attractive forces. The most important and distinctive feature These forces are their universality, since they act without exception between all atoms and molecules.

Hydrogen bonds affect the physical (boiling point, melting point, volatility, viscosity, spectral characteristics) and chemical (acid-base) properties of compounds.

Intermolecular hydrogen bonds cause the association of molecules, which leads to an increase in the boiling and melting temperatures of the substance. For example, ethyl alcohol C 2 H 5 OH, capable of association, boils at +78.3°C, and dimethyl ether CH 3 OCH 3, which does not form hydrogen bonds, boils only at 24°C ( molecular formula both substances C 2 H 6 O).

The formation of H-bonds with solvent molecules improves solubility. So, methyl and ethyl alcohols(CH 3 OH, C 2 H 5 OH), forming H-bonds with water molecules, dissolve indefinitely in it.

Intramolecular hydrogen bond is formed with a favorable spatial arrangement of the corresponding groups of atoms in the molecule and specifically affects the properties. For example, the H-bond within salicylic acid molecules increases its acidity.

Hydrogen bonds and their influence on the properties of matter

It is also currently believed that hydrogen chemical bonds can be weak and strong.

They differ from each other in energy and bond length (distance between atoms):

1. Hydrogen bonds are weak. Energy - 10-30 kJ/mol, bond length - 30. All substances listed above are examples of normal or weak hydrogen bonds.

2. Hydrogen bonds are strong. Energy - 400 kJ/mol, length - 23-24.