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Файл:Carbohydrates. Bioenergetics. Study manual
.pdf
MINISTRY OF SCIENCE AND HIGHER EDUCATION
OF RUSSIAN FEDERATION
FEDERAL STATE BUDGETARY EDUCATIONAL
INSTITUTION OF HIGHER EDUCATION
“KABARDINO-BALKARIAN STATE UNIVERSITY
after KH.M. BERBEKOV”
.
CARBOHYDRATES. BIOENERGETICS
Study manual
Manual of biological chemistry for independent work
of students specialties "General Medicine", "Dentistry"
Nalchik
KBSU
2022
УДК 577 (075)
УДК 577 (075)
ББК 28.072 я73
Беева Д.А., Мукожева Р.А., Гринева Л.Г.,
Паштова Л.Р., Балаева С.М., 2022
ББК 28.072 я73
К21
Reviewer:
Department of Chemistry and Methods of Teaching Chemistry
of the Chechen State Pedagogical University
сandidate of Biological Sciences, Acting Head of the Department of Botany,
Zoology and Ecology of the Chechen State University
Z.I. Iriskhanova
Authors: Beeva D.A., Mukozheva R.A., Grineva L.G.,
Pashtova L.R., Balaeva S.M.
К21 Carbohydrates. Bioenergetics : study manual / D. A. Beeva, R. A. Mu-
The publication contains material on the structure and functions of carbohydrates, the main schemes of their transformations are given, the processes of energy
metabolism in the body, the structure and functions of the respiratory chain are considered, as well as questions and tasks for independent work of foreign students
It is intended for independent work of students of the specialties "General
Medicine", "Dentistry".
kozheva, L. G. Grineva, L. R. Pashtova, S. M. Balaeva ; Ministry of Science and Higher Education, Kabardino-Balkarian State University
named after H. M. Berbekov. – Nalchik : Kab.-Bulk. un-t, 2022. – 80 p. –
Bibliogr. : 78-79 p. – 50 copies. – Text : direct.
CONTENT
INTRODUCTION …………………………………………………………….
4
CHAPTER I. CARBOHYDRATES ……………………………
5
1.1. Monosaccharides …………………………………………………………
6
1.2. Oligosaccharides …………………………………………………………
16
1.3. Polysaccharides …………………………………………………………..
17
1.4. Individual members of carbohydrates ……………………………………
19
1.5. The biological role and function of carbohydrates in the body.………….
24
1.6. Digestion and absorption of carbohydrates ………………………………
25
1.7. The breakdown of glucose. Glycolysis …………………………………..
26
1.8. The pentose phosphate pathway of glucose oxidation …………………...
30
1.9. Gluconeogenesis …………………………………………………………
32
1.10. Glycogen. The breakdown and glycogen synthesis …………………….
36
1.11. Regulation of the level of glucose in the blood …………………………
39
1.12. Pathology of carbohydrate metabolism …………………………………
40
1.13. Standards of solving tasks ………………………………………………
45
Situational tasks ………………………………………………………............
50
CHAPTER II. BIOENERGETICS ……………………………………………
53
2.1. Energy metabolism ……………………………………………………….
53
2.2. Macroergic compounds …………………………………………………..
54
2.3. Biological oxidation ……………………………………………………...
55
2.4. The tricarboxylic acid cycle (Krebs cycle) ………………………………
56
2.5. Respiratory chain ………………………………………………………...
60
2.6. Free radical oxidation …………………………………………………….
69
2.7. Deactivation of xenobiotics ………………………………………………
71
Situational tasks ………………………………………………………………
73
LITERATURE ………………………………………………………………..
78
INTRODUCTION
"...the happy medic without
knowledge of chemistry is committed can not be..."
M.V. Lomonosov,
"The Word about the benefits
of chemistry", 1751 y.
This manual is intended for medical students as an auxiliary material in the
study of biochemical discipline, one of the fundamental disciplines that provide
training of a qualified physician. The manual deals with the topic of "Carbohydrates" and "Bioenergy", which are some of the key issues in biochemistry are structure, function, properties of carbohydrates and basic metabolic processes, which
they undergo in the human body, the mechanisms of metabolism and energy.
An important place in publishing the issues of enzymatic and hormonal regulation of carbohydrate metabolism, hereditary and acquired pathological disorders,
oxidative processes in the human body. Tasks and examples for independent work
will help to assess the level of assimilation of the section of biochemistry.
CHAPTER 1
Carbohydrates
Carbohydrates are among the most common naturally occurring organic compounds. In the biosphere of carbohydrates contains more than all other organic matter combined. In plants, carbohydrates make up 80 % of the total weight, in animal
organisms; their share does not exceed 2 %. Among them are the relatively simple
connections to the largest macromolecules (polymers), molecular weight of which
can reach several million. The most common D-glucose and polysaccharides cellulose and starch.
Along with nucleic acids and proteins, carbohydrates are essential components
involved in almost all processes that occur in living organisms. The main functions
of carbohydrates in biological systems are energy and structural. Indeed, carbohydrates play a Central role in accumulation, storage and transport of energy in all living organisms, and the emergence in nature of the supporting structures on the basis
of polysaccharides (wood, plants or shells of arthropods) occurred long before the
advent of skeletons based on calcium phosphate. In addition to these features, complex oligosaccharides are used for specific cell-cell recognition, and
D-ribose and D-deoxyribose are part of nucleic acids (RNA and DNA) keepers
and carriers of genetic information. Some carbohydrates and their derivatives are
drugs, e.g., antibiotics.
A stocks carbohydrate in the form of glycogen in the human body is 2 % by
weight. The bulk of it (2/3) is in the muscles, 1/3 in the liver. In the blood contains
100–110 mg of glucose and its concentration depends on the osmotic pressure of
blood. A chronic shortage of carbohydrates leads to depletionof glycogen stores in
the liver and the deposition of fat in its cells. This can cause the so-called fatty degeneration of the liver and its dysfunction.
Thus, in order to understand the nature of the processes occurring in nature in
General and humans in particular, and purposefully influence on them, fighting off
infections and diseases, it is necessary to know and to develop the chemistry of carbohydrates.
Classification of carbohydrates
Carbohydrates (sugars) the common name of a broad class of natural organic
compounds containing an unbranched chain of several atoms of carbon, a carbonyl
group and several hydroxyl groups. In other words, it polyoxycarbonyl connection,
which describes the gross formula Cx(H2O)y, and their derivatives.
The simplest representatives of carbohydrates are monosaccharides (from the
Greek. monos: single; sacchar: sugar), corresponding to the formula (CH2O)
where x = 3 ÷ 9.
x
Depending on the number of monosaccharide residues in the molecule, carbo-
ALDOSES
KETOSES
C
CH2OH
O
H OH
H OH
H OH
H
C
CH2OH
O
H OH
OH H
H OH
H
CH2OH
C
CH2OH
O
H OH
H OH
CH2OH
C
CH2OH
O
OH H
H OH
ALDOPENTOSES
D-ribose
D-xylose
KETOPENTOSES
D-ribulose
D-xylulose
hydrates are divided into mono-, oligo- and polysaccharides. Polysaccharides, in turn,
are divided into the homopolisaccharides, consisting of residues of the same mono-
saccharaides, and the heteropolysaccharides, consisting of the remnants of various
monosaccharaides. Separate groups areof mixed carbohydrate-containing biopolymers. The classification of carbohydrates can be represented in the form of a diagram:
sis. The number of carbon atoms in the molecule of the monosaccharide distinguish
triose (3 carbon atoms), tetrose (4 carbon atoms), pentose (5 carbons), hexose
(6 carbon atoms), etc. Monosaccharaides are divided by type of functional groups on
polyhydroxyvalerate (aldose – containing aldehyde group) and polyhydroxyethyl
(ketosis – contain a ketone group):
1.1. Monosaccharides
Monosaccharaides are simple carbohydrates that do not undergo hydroly-
C
CH2OH
O
H OH
OH H
H OH
H OH
H
C
CH2OH
O
H OH
OH H
OH H
H OH
H
CH2OH
C
CH2OH
O
OH H
H OH
H OH
CH2OH
C
CH2OH
O
OH H
OH H
H OH
ALDOHEXOSES
D-glucose
D-galactose
KETOHEXOSES
D-fructose
D-tagatose
(hemiacetals).
group of the monosaccharide with one of its hydroxyl groups:
In aqueous solutions of monosacharaides exist in two forms: open and cyclic
The formation of cyclic forms occurs due to the engagement of the carbonyl
Cyclic forms of monosaccharaides are represented by Haworths projections.
Carbohydrates with six-membered cycles are called pyranose; five-membered
cycles furanose.
In a number of aldohexose pyranose cycle is formed by the interaction of carbonyl group with the hydroxyl at C-5; furanose cycle is formed with the participation in the reaction of the hydroxyl at C-4.
The symmetric structure of the molecule pyranose form of the carbohydrate
imparts a higher thermodynamic stability; therefore, in solution the content of the
pyranose form of the carbohydrate is higher than furanoses.
The interaction of carbonyl and hydroxyl groups of aldose a new asymmetric
(chiral) centre in s-1 is formed, which leads to the formation of another pair of
stereoisomers which are called the anomers (and an omers). Formation of and
-anomers are typical for pyranose and furanose forms:
The nature of the anomer depends on which solvent was recrystallized.So, due the
recrystallization of D-glucose from the alcohol or water formed -D-glucopyranose.
Upon recrystallization from pyridine formed -D-glucopyranose. They markedly
differ in the value of the specific rotation: for and -anomers, these values are re-
spectively +1120and +190.
In the solution of each anomers over time, there is a gradual change in specific
rotation to achieve a constant value (the same for solutions of both anomers) is equal
to +52,50.
The time variation of the rotation angle of the plane of polarization of light by
solutions of carbohydrates is called mutarotation. The chemical essence of the phenomenon consists in the ability of monosaccharaides (monosaccharide or links in the
structure of oligo - and polysaccharides) to exist in solution as equilibrium mixtures
of tautomers of various forms cyclic (in the form of pyranose and furanose cycles)
and open.
This kind of tautomerism is called cyclo-oxo-tautomerism.
In solutions the equilibrium between the four cyclic tautomers of monosaccharaides
is established through an open form (oxo-form). Interconversion of and -anomers
of each other through the intermediate oxo-form called anomerisation.
Thus, in the solution D-glucose exists in the form of tautomers 5: and anomers of pyranose and furanose ciclyc forms and oxo-forms.
In a mixture of tautomers dominate pyranose form. Oxo-form and tautomers
with furanose cycles are contained in small quantities due to their lower thermodynamic stability.
However, despite the low content of oxo-form, glucose enters into reactions
typical for aldehyde groups.
Conformation of monosaccharides
Using X-ray diffraction analysis, it was found that and -anomers of monosaccharaides have different chairs conformation of pyranose cycle.So, in - anomer
of D-glucopyranose the aldehyde group is in equatorial position (location semi-acetic
group coincides with the cycle axis of symmetry), and in -anomer in the axial posi-
tion (location of semi-acetic group does not coincide with the axis of symmetry):
The predominant formation, as well as the higher prevalence of -anomers in
nature, is explained by its greater thermodynamic stability than -anomeric one.
The same ratio of anomers is observed in D-galactopyranose. In D-mannopyranose in a mixture of tautomers predominates anomer that is associated with
the axial location of the OH-group at C-2. Conformational structure of monosaccharaides largely determines the spatial structure of chains of polysaccharides.
Derivatives of monosaccharides
When one or more OH-groups are replaced by a hydrogen atom or other functional groups, monosaccharide derivatives, called deoxysaccharose, are formed.
Important cases where one or more hydroxyl groups replaced by a hydrogen
atom. It relates to a structural component of nucleic acids 2-deoxy-D-ribose. 6-
deoxygalactose (fucose) is a part of many oligosaccharides of animal origin:
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