-To print this articleStudy on homogeneity of protein drugs and allocation of separate protein fractions produced by various methods, the most important of which are based on application of the ultracentrifuge, electrophoresis, chromatography, as well as on the study of the solubility of proteins.
1. Methods for separation of proteins and amino acids, based on the differences in molecular weight substances:
and) differential centrifugation. In an ultracentrifuge first deposited the heavier molecules, then less severe.
b) gel-filtration. With this method, chromatographic column filled porous granules strongly hydrated carbohydrate polymer, more often than not sefadeksa (Special processed derivatives of high molecular weight carbohydrate dextran). When filtering through the column the mixture of low-molecular and macromolecular proteins are small protein molecules, penetrating through the pores inside granules sefadeksa, will occur on the column more slowly, than whites, molecules which do not fit into the pores of pellets and therefore faster flow from speakers.
2. Methods for separation of proteins and amino acids, based on differences in their acid-base properties (or differences in their electrical charges):
and) electrophoresis method. The meaning of electrophoresis is in the Division are in solution in the electric field of substances based on differences in their electrical charges. Electrophoretic study of protein typically produced at several pH values, unnecessarily. installed, that if one product pH protein behaves like a homogeneous substance, When another pH the same drug can be mixed.
In recent years, widespread electrophoresis of proteins and peptides solutions in various media-filter paper, wood or krahmal′nom powder, polyacrylamide gel. These methods allow you to analyze extremely small quantities of proteins.
b) disc electrophoresis in polyacrylamide gel, where a mixture of proteins is subjected to the simultaneous effects of electric field and gradient of Ph. It has a particularly high resolution.
Filtering through the gel, as well as polyacrylamide gel electrophoresis, widely used for fast approximate molecular weight determination of proteins.
in) ion-exchange chromatography. In ion-exchange chromatography as a carrier used polymers, the carriers themselves charge-ion exchange resin:
· cation exchange resin (charged negatively) -Exchange cations;
· anionoobmennye resin (positively charged) -exchanging anions.
For example, often used polisteroidnaâ sul′firovannaâ cation exchange resin. If the solution of amino acidic Wednesday, When loading columns positively charged amino acids and proteins replacing sodium with sulfide anion. When you add sodium hydroxyl pH increases; When the pH reaches, equal to isoelectric point of the protein molecules, amino acids lose their charge and become neutral. Under the influence of gravity amino acid comes out of the speakers, losing charge. Different proteins (amino acids) have different meanings izoèlektričeskih points.
3. Separation methods, based on differences in substances solubility:
and) method of fractionation of proteins of salt solutions. Based on the, that each individual protein is precipitated from the mixture of shared with some varying concentrations of salt, While other proteins at a given concentration of salt remains in solution. The process of deposition of protein solution under the influence of salt is called vysalivaniem. When further saturation salt falls following individual protein and, thus, You can select one after another relatively clean individual proteins.
b) distributing chromatography on paper. This method is based on varying degrees of distribution of the components of the mixture between the two liquid phases nesmešivaûŝimisâ (Mobile and stationary) and is, that drop of protein hydrolysate put on strip packing paper, one end of which is dipped in organic solvent. The solvent under the influence of capillary forces absorbed by paper and, passing along the strip of paper, carries for an amino acid.
Travel speed amino acids on paper depends on their chemical structure and ability to dissolve in mobile and stationary solvents. As mobile use saturated solvent phenol, n-butyl alcohol, etc. Stationary solvent is water, couples which saturate the paper. The smaller the solubility of amino acids in water and the more their solubility, for example, the phenol is, the faster they move the front followed by organic solvent.
4. Determination of primary structure of protein
Most responsible procedure when establishing the primary structure of proteins is to determine the sequence of amino acid residues. Currently this work lead mostly either fenilizotiocianatnym Edman method.
Edman method is implemented in a specially created for this purpose, the device, called sequenzer (from sequence-sequence). Edman method comes down to processing protein peptide or phenyl isothiocyanate, attached via p-end amino acid to the inert media (polystyrene or porous glass) in column sekvenatora. After washing the column solvents (methanol, ethylene dichloride) the resulting expose feniltiokarbamilpeptid waterless triftoracetic acid, as a result of which released anilinotiozolinon and its N-end amino acid, a shortened one acid balance or peptide protein remains associated with carrier.
Section 3. NUCLEOTIDES AND NUCLEIC ACIDS
Lecture 4. Structure and function of nucleotides
1. General characteristics of nucleotides
Nucleotides- complex organic substances, consisting of 3 required components:
1) nucleobase;
2) pâtiuglerodnogo sugar;
3) balance phosphoric acid.
Complex organic compounds, consisting only of the nucleobase and sugar-pentoses, called "nukes". Therefore, nucleotides-phosphate esters of nucleoside.
Nitrogenous bases
Nucleobase derive two heterocyclic compounds-purine and pyrimidine:
· purine nucleobase:
Adenine Guanine
· pyrimidine nucleobase:
Uracil Cytosine Thymine
Pâtiuglerodnye sugar:
β-ribose β-Deoxyribose
Phosphoric acid
The composition of the remainder belongs necessarily nucleotides phosphoric (phosphoric) acid.
In addition to the above three mandatory components, the composition of the molecules may include nucleotide and other functional groups.
In the formation of nucleosides first atom ribose (dezoksiribozy) binds to the N-1 or N-series Atom 9 Atom purine bases.
With ribozoj connect adenine, forming adenosine; guanine, form guanozin; cytosine, forming Cytidine; uracil, to form uridine.
With dezoksiribozoj connect adenine, guanine, cytosine and thymine, forming dezoksiadenozin respectively, dezoksiguanosin, deoxycytidine, Thymidine.
The most common in nature according to 5 status of sugar and it does not indicate.
In the body are nucleotides nucleic acids monomers, or operated independently. Depending on, quantity in nucleotides represented by their main components, all nucleotides are divided into mononukleotidy, dinukleotidy and polynucleotides (polinukleinovye acid).
2. Structure and function of Mono- and dinukleotidov
Mono- and dinukleotidy are not part of nucleic acids; they operate independently. The composition of independent nucleotides as the sugar ribose is always.
The mononukleotidam include ATP, ADP, CORP, Coenzyme a and the other nucleotides.
ATP- nucleic acid:
ATP is the energy equivalent of cells, She is a mediator between the reactions, going to release energy (èkzergoničeskimi) and reactions, stacked with energy absorption (èndergoničeskimi). In other words, in the form of ATP stored energy cell, which is then used for processes of vital activity.
Chemical communication between different atoms in organic compounds are divided into 2 type:
1) normal
2) makroèrgičeskie
Normal connection -connection, If you experience or decay which change the level of free energy connections is 12,5 J/mol.
Makroèrgičeskie connection -connection, If you encounter or disintegration of which the level of free energy connection is 25-50 kJ/mol of a substance.
The concept of "makroèrgičeskaâ communication" takes into account the energy effect transformed by a chemical reaction of a substance with normal properties.
Links between remnants of phosphoric acid are makroèrgičeskimi if the hydrolysis energy is allocated. Such a connection called a wavy line.
1-th energy ATP molecules can only serve for 1-St reaction. ADP and AMP is not able to be source of energy.
In living cells are 3 how education ATF:
1) Substratum Baltic Word as phosphorylation.
2) Oxidative phosphorylation.
3) Fotosintetičeskoe phosphorylation.
Coenzyme A (Forehead). COA is an agent of the acetyl groups; involved in many processes. It is composed of adenine, ribose, pyrophosphate, Pantothenic acid (Vitamin b3) and tiolamin. Simplistic Coenzyme and is represented as the following formula: HS-KoA. When interacting with acetic acid and COA is formed by acetilkoènzim and, in a molecule which appears makroèrgičeskaâ (high-energy):
Acetilkoènzim And
Acetilkoènzim and is a key metabolite, which is not only the disintegration and synthesis of various substances, but the relationship between protein metabolism, lipids and carbohydrates.
The dinukleotidam are OVER, NADP, FAD, etc.
OVER- NICOTINAMIDE adenine dinucleotide;
NADP-nikotinamidadenin dinucleotide phosphate.
These included dinukleotidov NICOTINAMIDE (amide Nicotinic Acid, is an important vitamin - vitamin in the5). NADP molecule is identical in structure to the ABOVE with the only difference, that NADP with-3 Atom ribose IT group replaced the remainder of the molecule of phosphoric acid.
The molecules above and are capable of NFDF reversible oxidation and restoration (due to redox ability nikotinamida), They therefore participate as hydrogen carriers; in the biological oxidation reactions OVER and NADP are the cofactors of enzymes dehydrogenases.
The Structure OVER (oxidized form)
FAD-fads and trends. It consists of riboflavin (Vitamin b2).
FEDERAL Structure (oxidized form)
FAD, like other dinukleotidy, capable of reversibly oxidized and recover, attaching to its molecule 2 hydrogen atom, He therefore participates in biological oxidation as a hydrogen carrier. Is kofactorom dehydrogenases, as well, as above and NADP.
3. Structure and function of nucleic acids
The most remarkable property of living cells is their ability to reproduce with almost the utmost precision and not once or twice, as in hundreds and thousands of generations.
Living cells have this ability due to the presence in them of nucleic acids.
DNA-deoxyribonucleic acid;
RNA-ribonucleic acid.
DNA and RNA-macromolecular compounds, which are based on nucleotides, United 3, 5 - fosfodièfirnymi links. Their molecular mass is highly variable (from 15 thousand. to 1 billion).
Nucleic acids are well dissolved in fenolah; bad-weak acid solutions.
Differences between DNA and RNA:
1. Composed of DNA-adenine, guanine, cytosine, thymine;
composed of RNA-adenine, guanine, cytosine, uracil.
2. Composed of DNA-Deoxyribose; composed of RNA-ribose.
3. DNA dvuhcepočečnye; RNA-single.
Features of the structure of DNA
· DNA consists of two pravozakručennyh polinukleotidnyh spirals, sharing a common axis.
· Two chains of DNA antiparallel′ny, ie. 3 and 5 fosfodièfirnye bridges are oriented in opposite directions.
· Flat bases, hydrophobic, located in parallel planes and perpendicular to the long axis of spirals.
· Reason 2-x chains coupled. Opposite The A-T; on the contrary, Mr. TS;
Paired bases are complementary to each other.
Complementarity -spatial complementarities surfaces interacting molecules or parts thereof, tending to cause secondary linkages between them.
Between a and t occurs 2 hydrogen bonds; between g and c- 3 hydrogen bonds.
The remains of sugars and phosphate groups remain on the surface and molecules come into contact with water. Negatively charged residues of phosphoric acid group easily interact with proteins, dominated by the histone proteins-proteins, distinguished by its basic nature.
4. Nucleic acids differ in features.
The function of DNA-storage, Replication (doubling) and the transmission of hereditary information (hereditary information is information about the primary structure of proteins).
RNA functions are determined by the type of RNA.
Types Of Rna:
and) m-RNA-RNA or matrix-information.
Messenger RNA carries out the transfer function of the hereditary information of the cell nucleus from the DNA in the cytoplasm, to the site of protein synthesis.
Implementation of hereditary information-protein synthesis.
There are hundreds of thousands of species of m-RNA in a cell.
b) t-RNA-transport.
Migrates to the site of protein synthesis necessary amino acids.
in) r-RNA-ribosomal′naâ.
Ribosomes-organelle, performing functions of protein synthesis.
5. Nucleic acids differ in localization.
The main amount of DNA is located in the cell nucleus (in the composition of chromosomes). Part of the DNA is located in the mitochondria and chloroplasts (It is referred to as cytoplasmic DNA). RNA is in the cytoplasm.
4. Basic biochemical functions of nucleotides
Thus, nucleotides are joining a group of substances, that perform a variety of functions:
1. Are the building blocks of nucleic acids, participate in molecular mechanisms, by which genetic information is stored, is replicated and transcribed.
2. Play an important role in energy (phosphoric) Exchange, accumulation and transfer of energy.
3. Serve as cofactors of enzymes, belonging to different classes.
4. Play an important role in the synthesis and disintegration of carbohydrates, fatty acids and lipids.
5. Some of the nucleotides are the intermediaries in the complex processes of signal transduction (signal transmission in living cells).
Section 4. ENZYMES
Lecture 5. Structure, the action mechanism and classification of enzymes
1. Structure and basic properties of the enzymes
Enzymes (enzymes) -protein substance nature, present in all living cells and serve as catalysts for biochemical processes.
The composition of the enzymes are divided into:
1) simple-composed only of amino acids;
2) the complex is composed of 2-piece:
- of protein, which is called apofermentom and
- nebelkova part-cofactor.
Apofermenta complex and cofactor is called holofermentom.
No apoferment, Neither cofactor individually are not capable of catalyzing reaction. Functionally active only their complex.
Types of cofactors:
By its chemical nature cofactors can be represented as organic, and inorganic.
Organic cofactors can be divided into two groups:
1) prostetičeskie group-cofactors, which are strongly connected with apofermentom and, when selected from the body not detached from protein parts.
For example, FAD in the composition of the enzyme succinate dehydrogenase of Krebs cycle.
2) coenzymes are cofactors, connected to the apofermentami weak links and easily from him tiny: for example, OVER, NADP, and sometimes the FAD.
Inorganic cofactors represented by metal ions (most often iron ions, copper, manganese, zinc, etc.). Metal ions as cofactors or are directly involved in catalysis, either form bridges, bind to the enzyme with the substrate.
Substrate (S) -substance, chemical transformations which enzyme catalyzes.
The structure of the enzyme, or enzyme (E):
Because the substrate molecule usually smaller molecules of enzymes, then in direct contact with the substrate enters the only part of the molecules of the enzyme-active Center. And, the geometry of the surface of the substrate molecule is complementary surface active Center.
Active Center of enzymes-a unique combination of amino acid residues, provides interaction with the substrate molecule and participating in catalysis. Complex enzymes in the composition of the active site necessarily includes cofactor.
Active Center may have 2 plot:
· anchor (substrate);
· catalytic.
Anchor plot has a geometric similarity (compliance) the substrate molecule and provides the enzyme specificity.
Similarities between enzymes and catalysts by abiotic
1. Any catalyst (inorganic and organic) decreases the activation energy of molecules. Activation energy is the amount of energy in calories, required to translate all the molecules 1 mole substance 5th in activated status, ie. the State of the, in which they can engage in a chemical reaction.
2. Any catalyst can accelerate chemical reactions only, possible from the perspective of thermodynamics.
3. Catalysts do not change the direction of a chemical reaction.
4. Catalysts are not spent during the reaction.
Differences between the enzymes from inorganic catalysts
1. Catalysis proceeds in very mild conditions (T, Ph)
2. High efficiency: enzymes increase the rate of reaction
in 1010 - 1012 time.
Example: in the body there is the enzyme catalase (cofactor - Fe).
1 mg of iron in katalaze acts as a 10 t of inorganic iron.
3. The specificity of the action. Each enzyme speeds up only 1 reaction. Species specificity:
- absolute (1 the enzyme acts only on 1 substrate, for example, urease enzyme catalyzes the hydrolysis of urea);
- relative (1 enzyme can operate on a group of similar structure substrates).
4. The possibility of a fine and accurate regulation of speed of reaction conditions have changed Wednesday (due to the nature of the protein enzyme)
For each enzyme has its temperature optimum.
Example: body temperature- 36,6 Grad.; at t = 40-41grad. may be irreversible denaturation. At low temperatures, there has been a slowdown in the rate of enzymatic catalysis (due to Brownian motion of molecules).
Enzymes are very sensitive to changes in acidity Wednesday, in which they operate. Enzyme activity is manifested within rather narrow pH zone, called an optimum pH. Can be considered, each enzyme has a certain optimum concentration of protons, where it is most active.
PH change leads to a change in charges on the active Centre and the molecule as a whole; as a result, changes the conformation of the protein molecule, as a result of which disturbed the spatial conformity to the active site and substrate, so, the reaction rate is reduced.
5. Possibility of saturation of enzyme substrate (especially the kinetics).
6. Enzymatic catalysis is strictly programmed process (1 reaction; 1 substrate; 1 enzyme) -a series of elementary transformations of substances, strictly organized in space and time.
2. The mechanism of action of enzymes
The action of the enzyme is based on the formation of an enzyme-substrate complex. Under the influence of substrate changes the conformation of the enzyme, then change the substrate.
The mechanism of action of enzymes can be represented as the following scheme:
E + S → ES → EZ → EP → E + P
It is possible to allocate 4 phase:
1. Between substrate and enzyme originate connection (ES), in which connection connected ion, Covalent or other communication.
2. The substrate under the action of a bound enzyme undergoes changes (S→Z), making it more affordable for the corresponding reaction.
3. A chemical reaction occurs with formation of enzyme-produktnogo complex (EP).
4. The reaction products are released from the enzyme-produktnogo complex.
3. Nomenclature and classification of enzymes
Nomenclature of enzymes (rules education titles)
1. Random (random featured) -trivial
Example: papain (Carica papaja-wood).
2. Rational: substrate + "AZA" (lipids-lipase)
3. Systematic: substrate + type-catalyzed reaction + "AZA" (lactate dehydrogenase), or substrate + the name of the class, This enzyme belongs to + AZA» (lactate-oksidoreduktaza).
Classification of enzymes
Adopted in 1961 year.
The classification was based on type-catalyzed reaction:
1. Oxidoreductase (complex enzymes, catalytic redox reactions). Example: izocitratdegidrogenaza of the Krebs cycle.
2. Transferase (catalyze transfer reactions of functional groups or molecular residues between molecules). Example: kinase transferase-1-th stage of Glycolysis.
3. Hydrolase (simple enzymes, to catalyze the reaction of hydrolysis of starch, oligosaccharides, fat). Examples: lipase, Invertase, maltase, etc.
4. Lyase (catalyze negidrolitičeskoe chip away from the substrata of certain groups of atoms with the formation of double bonds, or accession on the double bond). Example: fructose-bisphosphate aldolase from Glycolysis.
5. Isomerase (catalyze isomerization-the spatial or restructuring within the 1-th molecules). Example: triozofosfatizomeraza of Glycolysis.
6. Ligase activity (often referred to as sintetazami) -catalyze reactions of synthesis, associated with the collapse of the energy-rich links (ATF).
Each enzyme has a 4-digit code: class-subclass-podpodklass- the individual number of the enzyme.
4. Kinetics of enzymatic reactions
The peculiarity of the kinetics of enzyme reactions is to saturate the enzyme substrate, where a further increase [S] does not increase the rate of reaction. Empirically found, that the kinetics of enzymatic reactions can be expressed as follows:
Concentration of substrate, which enzyme reaches saturation, is a constant characteristic for each particular enzyme.
Kinetics of enzymatic reactions can be described by the equation, that was output by the theoretical scientists Making and Menten kinetics, and in honor of them was named.
Michaelis Equation - Menten kinetics
Tom Michaelis constant. It is this concentration of substrate, where the reaction rate is half of the maximum.
Michaelis constant characterizes the affinity of the enzyme to substrate: the smaller this constant, the greater the affinity of the enzyme to substrate, the better reaction.
5. Regulation of enzymatic processes in the cell
Numerous ways of regulation of enzymatic processes can be divided into two groups:
1. Regulation of enzyme content by changing the speed of its synthesis and decay. It should be noted the following processes:
repression is repression (or reduce) enzyme synthesis speed;
induction is the process of speeding up synthesis enzymes under the influence of specific low-molecular compounds-inductors.
2. Regulation of activity available in the cell enzymes.
and) by temperature changes, pH values, the amount of substrate, cofactors, etc.;
b) allosteričeskaâ regulation (characteristic only for allosteričeskih enzymes). Enzymes called Allosteričeskimi, but the Active Center with an additional Center associate (allosteric Center). Activity of allosteričeskih enzymes is regulated by changing the conformation of molecules of enzymes, caused by accession of the special allosteričeskomu cent to metabolite. Metabolite-regulator (allosteric effector) performs the functions of either the Activator, or inhibitor;
in) Covalent modification of enzymes-regulation of catalytic activity of enzymes can be due to Covalent phosphate group of nucleotide or accession. For example, that form of glycogen phosphorylase has higher catalytic activity;
g) changes in the activity of enzymes using activators-chemical compounds, increasing the activity of enzymes (for example, the amino acid cysteine and Glutathione is a tripeptide activate many proteases).
d) changes in the activity of enzymes using inhibitors-compounds, suppressing the activity of enzymes.
Inhibition of
Inhibition of -the reduction or complete inhibition of enzyme activity under the influence of certain substances (inhibitors).
The inhibition can be two main types: nebratimoe and reversible.
When the irreversible inhibition of the enzyme and inhibitor form nedissociiruûŝij complex. Irreversible inhibition in the body is rare, and if it is, due to substances, coming from outside.
When reversible inhibition of the enzyme and inhibitor form complex dissociative.
Reversible inhibition, in turn, divided into competitive and non-competitive.
Competitive inhibition -inhibition, in which the substrate and inhibitor have similar structure and compete for the active enzyme cent. Competitive inhibition in the body occurs frequently and is a way of regulating the activity of the enzyme.
The reaction speed when competitive inhibition depends on the ratio of the concentrations of the substrate and inhibitor. The higher the concentration of substrate, the higher the probability of formation of complex, the higher the rate of reaction. Thus, competitive inhibition can be suppressed by increasing the concentration of substrate.
Uncompetitive inhibition -inhibition, in which the substrate and inhibitor interact with different parts of the molecule of the enzyme. When the inhibitor, connecting with the enzyme molecule, so modifies its structure, that the maximum rate of reaction is impossible.
With the increase in the concentration of substrate inhibition of nekonkurentnom does not resolve inhibitor. Uncompetitive inhibition in the body, as a rule, associated with the arrival of the body of heavy metals.
Section 5. CARBOHYDRATES AND THEIR EXCHANGE
Lecture 6. Chemical structure and properties of carbohydrates
1. General characteristics and classification of carbohydrates
The carbohydrates are compounds, with a variety and often totally opposite properties. Among them are substances with a low molecular weight and high molecular weight, crystalline and amorphous, water soluble and insoluble it completely, capable to oxidize and relatively resistant to the effects of oxidants.
General formula, characteristic for the vast number of carbohydrates, Withn(N2In)m
On the chemical nature of carbohydrates are divided into:
· Monosaccharides (simple sugars);
· oligosaccharides;
· polysaccharides.
Monosaccharides contain 3-8 carbon atoms and are not subjected to hydrolysis with the formation of simple hydrocarbons.
Oligosaccharides are polymers of Monosaccharides, that contain 2-10 the remainder of the Monosaccharides.
Polysaccharides are polymers of Monosaccharides, that contain more than 10 remnants of Monosaccharides.
2. Structure, properties and functions of Monosaccharides
Monosaccharides are divided into the following groups:
1. By number of carbon atoms:
· Triose (3)
· Tetrose (4)
· Pentose (5)
· Hexose (6)
· Heptose (7)
· Octose (8)
2. Chemical structure:
· Aldose
· Ketozy
All Monosaccharides are alcohols, or al′degidospirtami, or ketospirtami. In their molecules, as a rule, the number of carbon atoms is equal to the number of molecules of water (ie. m = n).
D-glucose (al′doza) D-fructose (ketosis)
Aldose and ketozy are isomers.
Basic chemical properties of Monosaccharides:
1.Mutarotation-anomera transition from one form to another (for example, α-glucose →β-glucose). Anomerami purposes enantiomeric forms of monosaccharides called, the distinguished position of hydroxyl poluacetal′nogo.
2. Restore to polyatomic alcohol (for example, glucose is restored to electricity, ribose-up to ribita).
3. Oxidation with formation of the corresponding acids (for example, Depending on the okislâemoj group of glucose can form glûkonovuû, glûkuronovuû and glûkarovuû acid).
4. Èpimerizaciâ (for example, in alkalescent Wednesday D-glucose is in equilibrium with the ketogeksozoj (D-fructose) and al′dogeksozoj (D-mannozoj).
5. Formation of glycosides. Condensation anomernoj HE band with alcohol grouping molecules leads to the formation of o-glycosides. It is through these relationships built oligo- and polysaccharides. When communicating with groups he anomernoj NH2-the group formed N-glycosides.
6. Èterifikaciâ. Hydroxyl group of monosaccharides to form esters with different acids. In particular metabolism plays an important role in phosphorylation of sugars.
7. The ability to react with nitrogen-containing compounds at high temperature with the formation of specific substances stained-melanoidinov.
8. The ability of glucose (and other water) be subject to splitting (by Glycolysis) and sbraživaniû microorganisms.
The main functions of Monosaccharides:
1. Energy (Monosaccharides are easily split, emitting energy, which is spent on education ATF).
2. Plastic (metabolic). Monosaccharides are the precursors for the formation of many important substances: stand and structural polysaccharides, amino acids, fatty acids, Glycerin, etc.
3. Structure, properties and functions of oligosaccharides
Oligosaccharides are distinguished by the following indicators:
1. The number of monosaccharide.
2. Qualitative composition.
3. Nature of Glycoside linkage between Monosaccharides.
In solutions of monosaccharides are always present in the circular form; the composition of oligo- and they are also polysaccharides in circular form.
The first carbon atom, coupled with oxygen, is the most reactive. As a rule, the link is formed by glikozidnogo (poluacetal′nogo) hydroxyl.
For some properties are characteristic of oligosaccharides, marked for Monosaccharides. It should also be noted, that oligosaccharides, entering the human body with food, in the gastrointestinal tract are subjected to hydrolysis to their structural blocks-monosaccharide. Therefore the cells they are already in the form of simple sugars and, accordingly, perform the same functions, that and Monosaccharides.
The most popular are oligosaccharides of disaccharides. Consider the chemical composition of the most important of them.
Sucrose consists of residues α-glucose and β-fructose, United β-Glycoside (or fruktozidnoj) communication. Hydrolysis of sucrose occurs when the enzyme Invertase participation (sucrase):
sucrose α-glucose β-fructose
Invertase in large quantities contained in yeast and in the gut organisms. A mixture of glucose and fructose in equal quantities, which is formed during the hydrolysis of sucrose, called recurrences of sugar.
Maltose -disaccharide, consisting of 2-x residues α-glucose. This is the basic product of starch hydrolysis.
Maltose → α-glucose + α-glucose
Maltose hydrolysis takes place with the participation of the enzyme mal′tazy.
Is maltase in saliva and pancreatic juice.
Lactose is milk sugar, formed in an organism of animals.
Lactose = β-Galactose + α-glucose is catalyzed by the enzyme lactose-hydrolysed lactaza.
Lactase is very active in infants; Some adult lactase is not saved, that entails intolerance of milk.
4. Structure, properties and function of polysaccharides
Polysaccharides are divided into gomosaharidy and geterosaharidy.
In composition gomosaharidov includes one type of monosaccharide. If monomer-fructose, the fructan nzyvaetsâ polysaccharide; Galactose-galaktan; glucose-glucan.
Monomers geteropolisaharidov are Monosaccharides 2 or more types. For example, arabinose and glucose are part arabinoglûkanov; arabinose and Xylose-of arabinoxylans.
Starch (gomosaharid) -replacement of plant polysaccharide; существует в 2-х формах: амилоза и амилопектин.
Амилоза – линейный полисахарид, consists of residues α-glucose, United α -1, 4 communication.
Амилопектин – разветвленный полисахарид, в котором на каждые 12 остатков глюкозы, United α -1, 4 communication, have α -1, 6 link.
Эти вещества сильно различаются по своим физическим и химическим свойствам. So, for example, от йода амилоза окрашивается в синий цвет, а амилопектин – в красно-фиолетовый. Они различаются и по растворимости: амилоза легко растворяется в теплой воде и дает растворы со сравнительно невысокой вязкостью, в то время как амилопектин растворяется в воде лишь при нагревании под давлением и дает очень вязкие растворы.
Гликоген(«животный крахмал») – по строению сходен с крахмалом, но характеризуется большей разветвленностью.
Is a reserve nutrient (formed mainly in the liver and muscles).
Cellulose (fiber) -polysaccharide, consisting of a large number of residues β-glûkopiranozy.
Function of polysaccharides:
1. Supply of nutrients (starch, glycogen is the most common substances).
2. Sources of energy (If you are using them as sources of energy, they must first undergo breakdown to Monosaccharides).
3. Structural (cellulose-forms the cell walls in plants, chitin-animals, murein-bacteria).