α-amino acids can covalently bind each other with peptide connections.A carboxyl group of one amino acid is covalently associated with an amino group of another amino acid. In this case, it arises Co-Nh.-R Communication called peptide bond. In this case, the water molecule is cleaving.

Using peptide bonds from amino acids, proteins and peptides are formed. Peptides containing up to 10 amino acids call oligopeptides.Often, in the title of such molecules indicate the number of amino acids included in the oligopeptide: tripipeptide, pentapeptide, octapeptide, etc. Peptides containing more than 10 amino acids call "Polypeptides",and polypeptides consisting of more than 50 amino acid residues are usually called proteins. The monomers of amino acids that are part of the proteins are called "Amino-acid residues."Amino acid residue having a free amino group is called N-terminal and is written on the left, and having a free C-carboxyl group - C-terminal and is written on the right. Peptides are written and read from the N-terminus.

The relationship between the α-carbon atom and the α-amino group or the α-carboxyl group is capable of free rotations (although it is limited to the size and character of radicals), which allows the polypeptide chain to take various configurations.

Peptide bonds are usually located in the trans configuration, i.e. α-carbon atoms are located on different sides from peptide communication. As a result, the lateral radicals of amino acids are at the most remote distance from each other in space. Peptide ties are very durable and are covalent.

In the human body, many peptides are produced involved in the regulation of various biological processes and having high physiological activity. Such are whole line Hormones - oxytocin (9 amino acid residues), vasopressin (9), bradykinine (9) regulating tone of vessels, thyarolyberine (3), antibiotics - gramicidine, peptides with an anesthetic effect (enkephalins (5) and endorphins and other opioid peptides). The anesthetic effect of these peptides is hundreds of times greater than the analgesic effect of morphine;

The use of amino acids based on properties.

Amino acids, mainly α-amino acids, are necessary for protein synthesis in living organisms. For this amino acid, man and animals are obtained in the form of food containing various proteins. The latter are subjected in the digestive distribution path on individual amino acids, of which proteins characteristic of this body are then synthesized. Some amino acids are applied for medical purposes. Many amino acids serve for feeding animals.

Amino acid derivatives are used for fiber synthesis, such as Cappon.

Questions for self-control

· Write an electronic structure of nitrogen and hydrogen.

· Write an electronic and structural formula of ammonia.

· What is a hydrocarbon radical?

· What do you know hydrocarbon radicals?

· Replace in ammonia molecule one hydrogen per methyl radical.

· What do you think it is for the connection and what is it called?

· What substance will turn out if we replace the remaining hydrogen atoms on hydrocarbon radicals, for example, methyl?

· How will the properties of the compounds change?

· Determine the formula organicIf it is known that the density of its water vapor is 22.5, the mass fraction of carbon is 0.533, the mass fraction of hydrogen is 0.156 and the mass fraction of nitrogen is 0.311. (Answer: C 2 H 7 N.)

· Textbook G.E. Erudzitis, F.G.Feldman. Page 173, № 6, 7.

ü What is acid?

ü What is a functional group?

ü What do you remember the functional groups?

ü What is an amino group?

ü What properties have an amino group?

ü What properties are acid?

ü What do you think, what is the reaction of the medium to give a molecule containing an acidic and main group?

ü TEST

1 option.

1) The composition of amino acids include functional groups:

a) -nh2 and -on

b) -nh2 and -son

c) -nh2 and -son

d) -Oh and -son

2. Amino acids can be viewed as derivatives:

a) alkenes;

b) alcohols;

in) carboxylic acids;

d) carbohydrates.

3. Amino acids react

a) polymerization;

b) polycondestament;

c) neutralization.

4. Communication between amino acids in the polymer:

a) hydrogen;

b) ionic;

c) peptide.

5. An indispensable amino acids are ...

Option 2.

1. General formula amino acids:

a) R-CH2 (NH2) -Oson;

2. In a solution of amino acids Wednesday

a) alkaline;

b) neutral;

c) acid.

3. Amino acids can interact with each other at the same time forming:

a) carbohydrates;

b) nucleic acids;

c) polypeptides;

d) starch.

4. Amino acids - this ...

a) organic grounds;

b) acid

c) organic amphoteric compounds.

5. Amino acids apply in ...

ü What kind of inorganic substances can be obtained aminoacetic acid? Write the corresponding reaction equations.

ü A task.Determine the formula of amino acids, if the mass fractions of carbon, hydrogen, oxygen and nitrogen are equal, respectively: 48%, 9.34%, 42.67% and 18, 67%. Write all possible structural formulas and name them.

Plan lesson number 16

Discipline:Chemistry.

Subject:Proteins.

Objective: Examine the primary, secondary, tertiary protein structures. Chemical properties Proteins: burning, denaturation, hydrolysis, color reactions. Biological functions Proteins.

Planned results

Subject: formation of ideas about the place of chemistry in modern scientific picture peace; Understanding the role of chemistry in the formation of a horizon and functional literacy of a person to solve practical tasks;

MetaPered: using different species cognitive activity and the main intellectual operations (setting the problem, formulating hypotheses, analysis and synthesis, comparisons, generalizations, systematization, identify causal relations, search for analogs, formulation of conclusions) to solve the task;

Personal: a sense of pride and respect for the history and achievements of domestic chemical science; Chemically competent behavior in professional activity and in everyday life when handling chemicals, materials and processes;

Time rate:2 hours

Type of classes:Lecture.

Plan lesson:

Equipment:Textbook.

Literature:

1. Chemistry grade 10: studies. For general education. organizations with adj. on an electron. Media (DVD) / G.E. Rudzitis, F.G. Feldman. - M.: Enlightenment, 2014. -208 C.: Il.

2. Chemistry for professions and specialties of technical profile: a textbook for the stud. media institutions. prof. Education / O.S. Gabrilyan, I.G. Outrium. - 5 - ed., Even. - M.: Publishing Center "Academy", 2017. - 272c., With color. Il.

Teacher:Tubaltseva Yu.N.

Theme 16. Proteins.

1. Proteins. Primary, secondary, tertiary protein structure.

2. Chemical properties of proteins: burning, denaturation, hydrolysis, color reactions.

3. Biological functions of proteins.

1) Proteins. Primary, secondary, tertiary protein structure.

1 – The composition of the protein: C - 54%, O - 23%, H - 7%, N - 17%, S - 2% and others: zn, p, fe, cu, mg, mn

In 1903, the German scientist E.G. Fisher offered a peptide theory, which became the key to the secret of the structure of the protein. Fisher suggested that proteins are polymers from amino acid residues connected by NH-CO peptide bond. The idea that proteins are polymeric formations, expressed in 1888 by the Russian scientist A.Ya. Danilevsky.

2 - Proteins - Navy - Proteins

"Protos" from Greek - "primary, most important." Proteins - natural polymers consisting of ak.

Mr (albumin) \u003d 36000

MR (MIOSINE) \u003d 150000

MR (hemoglobin) \u003d 68000

Mr (collagen) \u003d 350000

Mr (fibrinogen) \u003d 450000

Milk protein formula - casein C 1894 H 3021 O 576 N 468 S 21

Proteins are natural high molecular weight of natural compounds (biopolymers) constructed from alpha-amino acids connected by a special peptide bond. The protein includes 20 different amino acids, hence the huge variety of proteins with various combinations of amino acids. As from 33 letters of the alphabet, we can make an infinite number of words, so of 20 amino acids - an infinite set of proteins. In the human body there are up to 100,000 proteins.

The number of amino acid residues included in the molecules is different: insulin - 51, Mioglobin - 140. Hence the M R protein from 10,000 to several million.

Proteins are divided into proteins (simple proteins) and proteids (sophisticated proteins).

4 - 20 AK - "bricks" of a protein building, connecting them in a different order, you can build an innumerable set of substances with the most different properties. Chemists are trying to decipher the structure of protein molecules-giants. This task is very difficult: nature carefully hides the "drawings" for which these particles are built.

In 1888, Russian Biochemist A.Ya. Danilevsky pointed out that in protein molecules there are repeated peptide groups of atoms -to-n-

At the beginning of the twentieth century, the German scientist E. Fishera and other researchers managed to synthesize compounds into molecules, which included 18 residues of various ACs connected by peptide bonds.

5 - Primary protein structure is a sequential alternation of AK (PPC polypeptide chain). The spatial configuration of the protein molecule, resembling the spiral forms due to numerous hydrogen bonds between groups.

- co- and -nh-

Such a protein structure is called secondary. In the space, the spiral spiral of PPC forms the tertiary structure of the protein, which is supported by the interaction of different functional groups PPC.

-S-S- (disulfide bridge)

-Oson and -One (ester bridge)

-Son and -NH 2 (salt bridge)

Some protein macromolecules can be connected to each other and form large molecules. Polymer formations of proteins are called quaternary structures (hemoglobin only with such a structure is able to attach and transport about 2 to the body)

2) Chemical properties of proteins: burning, denaturation, hydrolysis, color reactions.

1. The proteins are characterized by reaction, as a result of which falls precipitate. But in some cases, the resulting precipitate is dissolved during an excess of water, and in others - irreversible coagulation of proteins occurs, i.e. denaturation.

Denaturation is a change in the tertiary and quaternary structures of protein macromolecules under the influence of external factors (increase or decrease in temperature, pressure, mechanical effects, the actions of chemical reagents, UV radiation, radiation, poisons, salts of heavy metals (lead, mercury, etc.))

Polypeptides are proteins that have an increased condensation degree. They have widespread among the organisms of both vegetable and animal origin. That is, here we are talking about the components that are mandatory. They differ in extreme diversity, and there is no edge of a clear nature between such substances and ordinary proteins. If we talk about the variety of such substances, then it should be noted that when they are formed, at least 20 amino acids of the protnogenic type are involved in this process, and if we talk about the number of isomers, then they can be infinity.

That is why protein type molecules have so many opportunities that are practically endless when it comes to their polyfunctionality. So, it is clear why proteins call the main all living things that are on earth. Proteins are also called one of the most difficult substances that have ever been formed by nature, they are also very unique. Just like protein, proteins contribute to the active development of living organisms.

If we say the most specifically, then we are talking about substances that are biopolymers based on amino acids containing no less than hundreds of amino acid residues. Moreover, there is also a division - there are substances that relate to a low molecular weight group, they include only a few dozen amino acid residues, there are also substances that relate to high molecular weight groups, there are significantly more residuals in them. The polypeptide is such a substance that is distinguished by a really big variety in its structure and organization.

Polypeptide groups

All these substances are in conjunction are divided into two groups, with this division, the features of their structure are taken into account, which have a direct impact on their functionality:

• The first group includes substances that are distinguished by a typical protein structure, that is, a linear type chain and amino acids are directly included. They are found in all living organisms, moreover, the greatest interest here have substances with increased hormone type activity.
• As for the second group, there are those compounds here, the structure of which has not the most typical protein features.

What is a polypeptide chain

The polypeptide chain represents the protein structure in which amino acids include, all of this has a solid connection with peptide type connections. If we talk about the primary structure, we are talking about the simplest level of the structure of a protein type molecule. Such an organizational form is highly stable.

When peptide bonds begin to form in the cells, then the activation of the carboxyl type of one amino acid begins the activation, and then it starts an active connection with another similar group. That is, polypeptide chains are characterized by constantly alternating fragments of such connections. There is a number of certain factors that have a significant effect on the form of the primary type structure, but this is not limited to. There is an active impact on the organizations of such a chain that have the highest level.

If we talk about the peculiarities of such an organizational form, then they are as follows:

• there is a regular alternation of structures related to hard type;
• there are sites that have relative mobility, they have the ability to rotate around the connections. It is the features of this kind that affect how the polypeptide chain is stacked in space. And with peptide chains can be carried out by different kind organizational moments Under the influence of many factors. It may be disconnected by one of the structures when the peptides are formed into a separate group and separated from one chain.

Stellic structure of secondary type

Here we are talking about the version of the chain styling in such a way that an ordered structure is organized, it becomes possible, due to hydrogen bonds between the peptide groups of one chain with the same groups of another chain. If you take into account the configuration of such a structure, then it can be:

1. Spiral type, such a name happened due to a peculiar form.
2. Layer-fold type.

If we talk about a spiral group, then this is such protein structurewhich is formed in the form of a helix, which is formed, without going beyond the limits of the polypeptide type chain. If speak about appearance, It is largely similar to the usual electric spiral, which is in the tile operating on electricity.

As for the layered-folded structure, the chain is distinguished by a curved configuration, its formation is carried out on the basis of hydrogen-type bonds, and here everything is limited to the limits of one section of a particular chain.

Amino acid monomers included in the polypeptides are called amino acid residues. Amino acid residue having a free amino group is called N-terminal and recorded on the left peptide chain, and having a free α-carbo-xyl group - C-terminal, and recorded on the right. The chain of repeating atoms -CH - NH- in the polyptate chain is called peptide casual.

The polypeptide chain has the following general view:

where R 1, R 2, R 3, ... R n is the amino acid radicals that form the side chain.

In the manifestation of biological functions of peptides and proteins, the electronic and spatial structure of the peptide group plays a major role:

The presence of a p-π-conjugation in the peptide group leads to a partial two-way communication of C - N connection. The length of the peptide bondage of C - n is 0.132 nm, and the length of the bond N - C α is 0.147 nm. The single connection of C - N in peptides by about 40% has the character of the double bond, and the double bond with \u003d O approximately 40% is single. This circumstance leads to two important consequences:

1) the imino group (- NH -) peptide communications does not have a markedly expressed ability to split or attach a proton;

2) Free rotation around the connection C - N is absent.

Partizing the boselity of communication C - n means that the peptide group is a flat section of the peptide chain. The planes of peptide groups are located at an angle to each other:

Around the bonds of C - with α and n - with α is possible rotation, although limited by the size and character of the radicals, which allows the polypeptide chain to take various configurations.

The peptide bond is the only covalent bond, with which the amino acid residues are connected to each other, forming the protein molecule.

Peptide bonds are usually located in the trans configuration, i.e. α-carbon atoms are located in different directions from peptide communications. As a result, the lateral radicals of amino acids are in the space at the most remote distance from each other.

Annclature peptide

With the name of the polypeptide to the name of all amino acid residues, besides the latter, suffix is \u200b\u200badded - il., the end of the amino acid has the end - iN.. For example, the peptide met-asp-tree-pro has the full name of the methone il. asparag il. shaft il. prol. in.

Acid-basic properties of peptides

Many short peptides were obtained in a pure crystalline form. The high temperatures of their melting indicate that the peptides are crystallized from the neutral solutions in the form of dipolar ions. Since none of the α-carboxyl groups and none of the α-amino groups involved in the formation of peptide bonds cannot be ionized in the pH range from 0 to 14, the acid-main properties of peptides are determined by the free NH 2 group of N-terminal residue and free carboxyl A group of the C-terminal residue of the peptide and those R-groups that are capable of ionization. In long peptide circuits, the number of ionized R-groups is usually large compared to two ionized groups of cross-residues of the peptide. Therefore, for the characteristics of the acid-main properties of peptides, we will consider short peptides.

The free α-amino group and the free end carboxyl group in peptides are separated by a much larger distance than in simple amino acids, and therefore electrostatic mutual-actions are weakened between them. PK values \u200b\u200bfor end carboxyl groups in peptides are slightly higher, and for terminal α-amino groups is slightly lower than in the corresponding free amino acids. In the R-groups in short peptides and in the respective free amino acids, the values \u200b\u200bof PK are not noticeably vary.

To determine the pH area in which the isoelectric point of the short peptide under study may be sufficiently compare the number of free amino groups and the number of free carboxyl groups, including N-and C-terminal groups. If the number of amino groups exceeds the number of carboxyl groups, the isoelectric peptide point will lie in an alkaline area of \u200b\u200bthe pH, as it is necessary to prevent the amino group to prevent protonation. If the number of carboxyl groups exceeds the number of amino groups, the isoelectric point will be located in an acidic pH region, since the acidic medium suppresses the dissociation of carboxyl groups.

The peptide bond is formed in the reaction of the amino group of one amino acid and the carboxyl group of the other with the release of the water molecule:

CH 3 -CH (NH 2) -COOH + CH 3 - CH (NH 2) -COOH → CH 3 -CH (NH 2) -CO-NH- (CH 3) CH-COOH + H 2 O

Amino acid associated with peptide bonds form a polypeptide chain. Peptide bond has a plane structure: atoms C, O and N are in SP 2-hybridization; at the n atom has a p-orbital with a different pair of electrons; A p-p-conjugate system is formed, leading to shortening C-N (0.132 nm) communication and rotation limit (the rotation barrier is ~ 63 kJ / mol). Peptide connection has mainly trance- Configuration relative to the plane of the peptide communication. A similar structure of the peptide communication affects the formation of the secondary and tertiary protein structure. Peptide communication - rigid, covalent, genetically deterministic. IN structural formulas It is depicted in the form of a single connection, but in fact, this connection between carbon and nitrogen is partially the dual connection:

This is caused by various electronegability of atoms C, N and O. Around the peptide bonding is not possible, all four atoms lie in the same plane, i.e. Compliannas. The rotation of other connections around the polypeptide island is fairly free.

The primary structure was opened by Professor of Kazan University A.Ya. Danilevsky in 1989 In 1913, E. Fisher was synthesized the first peptides. The sequence of amino acids for each protein is unique and enshrined genetically.

Tripeptide: Glycylalanillinyllizin

To determine the primary structure of a separate, chemically homogeneous polypeptide chain by hydrolysis, the amino acid composition is found: the ratio of each of the twenty amino acids in the sample of a homogeneous polypeptide. Then proceed to determine the chemical nature of the terminal amino acids of the polypeptide chain containing one free NH 2-group and one free coxy group.

To determine nature N-terminal amino acid A number of methods are proposed, in particular, the Saler method (for its development F. Sagnger was awarded Nobel Prize In 1958). This method is based on a 2,4-dinitrophluorbenzene polypeptide arylation reaction. The polypeptide solution is treated with 2,4-dinitrophluorbenzene, which interacts with a free α-amino group of peptide. After acid hydrolysis of the reaction product, only one amino acid turns to the reagent in the form of 2,4-dinitrophenylamino acid. Unlike other amino acids it has a yellow color. It is isolated from hydrolyzate and identified by chromatography.

For determining C-terminal amino acid Frequently use enzyme methods. Treatment of carboxypeptidase polypeptide, which breaks a peptide connection from the end of the peptide, which contains a free coxy group, leads to the release of C-terminal amino acid, the nature of which can be identified by chromatography. There are other methods for determining the C-terminal amino acid, in particular, the chemical method of akabori, based on the hydrazinolysis of the polypeptide.

The next stage of work is associated with the determination of the sequence of amino acids in the polypeptide. To do this, initially conduct partial (chemical and enzymant) hydrolysis of the polypeptide chain to short peptide fragments, the sequence of which can be accurately defined. After hydrolysis, with electrophoresis and chromatography, peptide cards are made. Then the sequence of amino acids in the selected peptides and the primary structure of the entire molecule are installed.

Capable of interconnect peptide sv. (Polymer molecule is formed).

Peptide communication - between the α-carboxyl group of one amino. andα-aminographer. Drug Amino ..

At the name, the suffix is \u200b\u200badded "-il", the last amino is added. Not change. Your name.

(Alanil-Seril-tryptophan)

Properties of peptide communications

1. Location of amino acid radicals in relation to C-N connection

2. Coplanarity - all atoms included in the peptide group are in the same plane, while "H" and "O" are located on different sides of the peptide bond.

3. The presence of ketforms (O-C \u003d N) and enol (O \u003d S-T-H) forms

4. Ability to form two hydrogen ties with other peptides

5. Peptide bond is partially the character of the double bond, the length is less than the single bond, is a rigid structure, rotation around it is difficult.

To detect proteins and peptide - buret reactions (from blue in purple)

4) Protein functions:

Structural proteins (collagen, keratin),

Fermented (pepsin, amylase),

Transport (transferin, albumin, hemoglobin),

Food (eggs eggs, cereals),

Contractile and motors (Aktin, Miosin, Tubulin),

Protective (immunoglobulins, thrombin, fibrinogen),

Regulatory (somatotropic hormone, adrenocorticotropic hormone, insulin).

Levels of the organization of the protein structure

Protein - sequence of amino. Related to each other peptide connections.

Peptide - amino. Not more than 10.

Polypeptide - from 10 to

The protein is more than 40 amino.

Primary structure -linear protein molecule, image. When connecting amino. in a chain.

polymorphism of protein- may pass inheritance and stay in the population

The sequence and ratio of amino acids in the primary structure determines the formation of secondary, tertiary and quaternary structures.

Secondary structure-fortune. pept. Groups with arr. water connections. There are 2 types of structure-laying in the form of a rope and a hormone machine.

Two variants of the secondary structure: α-helix (α-structure or paraleas.) And β-folded layer (β-structure or antipar.).

In one protein, as a rule, both structures are present, but in a different share ratio.

In globular proteins, the α-helix prevails, in the fibrillar - β-structure.

The secondary structure is formed only with the participation of hydrogen bonds between peptide groups: an oxygen atom of one group reacts with a second hydrogen atom, at the same time the oxygen of the second peptide group is associated with the third and so on.