Prezentacja programu PowerPoint

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The chemistry course
for medical students Lecturer Prof. dr Iwona
Katnik-Prastowska Adiunct dr Magda
Orczyk-Pawilowicz Department of Chemistry and
Immunochemistry Wroclaw, Bujwida 44a E-mail
office_at_immchem.am.wroc.pl
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• The chemistry course
• In winter semester
• Lectures
• 6, 13, 20, 27 October 2006 for Medical Students
• in November 2006 only for Dentristry Students
• The laboratory classes and seminars
• November and December 2006
• In December 2006 the final semester test
• In the 2nd semester in the 2006
• the chemistry course will be continued
• Seminars and lab
• The exam for medical students only

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• The main topics of the lectures
• for medical students
• Interaction in water solution
• Heterocyclic compounds
• Carbohydrates
• Lipids and some steroids
• Protein structures
• Globular and fiber proteins

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Carbohydrates are the most abundant class of
biological molecules ¾ of dry weight of
plants, 1 of body weight in animals
Sugars are present in all cells.
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The schedule of the lecture
Derivatives of monosaccharides with biological
activities

• Phosphate and sulphate esters
• Alditols
• Aldonic and uronic acids
• Deoxysugars
• Aminosugars
• Family of sialic acids
• N-acetylmuraminic acid
• Glycosides

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The glucose ?-D-Glucopyranose ?- D-Glucopyranose
?-D-glucose is present in blood at a relatively
constant concentration of 5.5 mM and it is
carried to all tissues
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5
4
1
3
2
It is primary source of energy for humans, the
nervous system, including brain, totally depend
on glucose.
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• Glucose
• and other monosaccharides
• carry a number of hydroxyl groups
• to which substituents
• might be attached.

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? Phosphate esters of monosaccharides mainly at
C1 and C6 Glucose-1-phoshate Galactose-1-phospha
te Glucose-6-phosphate Fructose-1,6-di-phosphates
Glyceraldehyde-3-phosphate They are important
intermediates in metabolism, which act as
activated compounds in many metabolic reactions
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?
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? Sugar phosphate esters exist under
physiological conditions as a mixture of the
mono- and di-anions
are quite acidic with pK values for the two
stages of phosphate ionization
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? Sulphate esters Sulphate groups are attached
mainly to sugar ring at carbons 6, 2 and 5.
They are commonly present in
glucosaminoglycans such as heparin, keratan
suphate and chondroitin sulphate. These
compounds exist under physiological conditions
as a mixture of the monoanions and dianions.
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?Reduction of monosaccharides
Aldehyde group reduction
hydroxyl group
Sugar
reduction Alditols
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?Reduction of D-Glucose
D-sorbitol is used as a sugar substitute for
diabetics and in manufacture of candies.
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? Alditols are mainly found in plant word
from D-mannose
from D-xylose
from erythrose
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? reduction ? D-rybitol,
Vit B2 riboflavin
D-rybitol is an component of riboflavin, and
flavin coenzymes.
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Family of inositoles, An component of some
lipids
The blood of birds contains inositol
hexaphosphate, that can bind to deoxyhemoglobin
having allostric effect
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? Oxidation of monosaccharides
At C1 in mild conditions Aldonic acid
(gluconic acid) At C6 Uronic acid
(Glucuronic, mannouronic, galactouronic acids)
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? The oxidation at C1
D-gluconic acid
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? Gluconic acid has tendency to internally
estrify, forming lactones
An example
Vit C
Gluconic acid
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Vitamin C Humans do not have the enzyme systems
required for the synthesis
Gamma lactone
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Vit.C oxidation to a biologically active
diketone. Vit C participate in a reducing
capacity in several biochemical reactions
Both forms are active
In turn, dehydroascorbinic acid (active)
is irreversible hydrolyzed to
diketogulonic acid, which is inactive.
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Vit.C prolonged deficiency in the diet results in
scurvy.
Scurve is to suspected if ascorbinic acid levels
fall bellow 1mg/ml
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? The oxidation at C6
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• The glucuronic acid is known to form
• glucosides in human organism.
• Such glucosides are named glucuronides.
• They help to remove from circulation some
  metabolites.
• Glucuronic acid present in animal cells
  participates in detoxication.

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At acid condition aspirin is hydrolysed to the
salicylic acid, which is insoluble in water
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The glucuronide of salicylic acid.
Such compond is water soluble and can be removed
with urine
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The glucuronic acid is an component of many
polysaccharides
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• At physiological pH
• the aldonic and uronic acids
• are acid compounds,
• They can dissociate H
• They can form salts
• with ions of Fe and Ca

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?Deoxy-sugars
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? Deoxy-pentose Compare the structures D-ribose
and deoxy-D-ribose
Both structures are components of nucleic acids
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? The most important deoxy-sugars
-OH group of sugar is replaced by H
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? Fucose 6-deoxy-L-galactose is the only
component of glycoconjugates of verterbrates
present in the L-configuration
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? Steric formula of L-fucose as compared to
D-galactose
6-deoxygalactose
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? Original chemical and biological properties
of L-fucose

• hydrophylic-hydrophobic nature due to the
  presence of hydroxyl group on carbon 2,3,4, and a
  methyl group on carbon 5
• is a part of the Lewis and ABO blood group
  substances

H
OH
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Oligosaccharide part

• Fucose is present in blood in very low
  concentration,
• It is bound to macromolecules named
  glycoproteins, exclusively at a terminal
  position,
• and fucose is not inserted into oligosaccharide
  chains,

Fuc
Fuc
Protein part
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? Amino sugars -OH group is replaced by an
often acetylated amino group.
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? The most common aminohexoses
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?? ABO blood group substances are glycans and
sugar derivatives play essential role
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??? Neuraminic acid (Neu) 5 amino-3,5-dideoxy-2-no
nolosonic acid.
The acidic nine carbons monosaccharide (N-acetylma
nnosamine pyruvic acid)
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??? N-acetyl-neuraminic acid (Neu5-Ac) 5
amino-acetylo-3,5-dideoxy-2-nonolosonic acid.
named sialic acid (SA).
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SA
Occurrence of sialic acid almost in all cells
(except some bacteria), mainly in bound
forms in N- and O-glycoproteins, in sialo-Lewis
antigens, in mucins, in glycolipids.
Protein part
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Sialic acid (SA).

• SA is attached to glycans of glycoproteins at
  terminal position by different ind of isomeric
  linkages
• The distribution of SA variants
• is species specific and depends on
• the cell type and its developmental stage
• They participate
• in reactions of biological recognitions.

SA
Protein part
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• Properties of sialic acid
• is relatively large molecule comparing with
  other monosaccharides have an influence on the
  structure of molecule to which it belong,
• carboxylic group is hydrophilic,
• can form hydrogen bonds,
• is charged negatively and the compounds to which
  sialic acid is attached has acidic character,
• it can protect molecule against proteolytic
  attack.

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??? N-acetylmuramic acid is a prominent
component of bacterial walls.
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• ??? Properties of NAM
• It has acidic character,
• it is polar substance,
• carboxylic group can form hydrogen bonds,
• protect the bacteria against proteolysis and
  denaturation

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??? In bacteria wall N-acetylmuraminic acid
(NAM) and N-acetylglucosamine (NAG) forms
copolymer with cross-linked short peptides
named peptidoglycan.
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The chemical structure of peptidoglycan
More information during seminars
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Monosaccharides and its derivatives
Resume
?Phosphate esters ? Sulphate esters ? Alditols ?
Aldonic and uronic acids ? Deoxysugars ?
Aminosugars
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Glycosidesand glycosidic bonds
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-OH group at C1 of saccharides is the most
reactive
C1
C1
-OH group at C1 of sugar can form compounds with
other molecules having free OH or -NH2 groups
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Both glycosides and oligo-/polysacharides are
built of compounds linked by glycoside bond
Glycosides
Molecule (non-sugar) with free OH or -NH2
groups (aglycone)
Monosaccharide with free -OH at C1
Oligosaccharide Polysaccharide
Monosaccharide
Monosaccharide
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• Glycosides
• A complex carbohydrate,
• which the OH on the anomeric carbon
• is replaced by other compound .
• So, it consists from two parts linked by
• glycoside bond
• Sugar
• Aglicon , which contains OH group
• These compounds are widely distributed
• in plants, but are also present in animal tissues
  as glucuronides.

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Glycoside bonds are formed between C1-OH of
sugar and OH and -NH2 groups of other compounds
Water is liberated
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Compare
A disaccharide
A glycoside
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Formation of glycosides An example
methyl-glucopyranoside
Glycoside bond can be a or ß form the anomeric
carbon of glycoside to an OR group
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The most of plant glycosides are toxic substances
in almond
They act as inhibitors of enzymes
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Properties The glycoside bonding is labile
Glycosides could be hydrolysed to sugar and
aglycone. In the case of glycosides the
mutarotation is not possible.
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Glycosides are widely distributed in plant
word. The most important glycosides Non-toxic F
lavonoids Anthocyans Tannins Toxic Cyanogennic
glycosides Digitoxin -A highly active glycoside
derived from digitalis and prescribed in the
treatment of certain cardiac conditions. Saponin
that form soapy lathers when mixed and agitated
with water, used in detergents, foaming agents,
and emulsifiers. Coumarins produced synthetically
and widely used in perfumes.
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Some of plant glycosides have a pharmacologic
effect. Synthetic glycosides were/are used as
medicines.
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These glycosides were indicated in treatment of
patients with heart failure
Digitalis purpurea Purple foxglove.
Canavalia ensiformis
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Some of plant glycosides have been used as
ingredients for food preparation.
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White and black mustards
Vanilla
Brassica nigra
The strong smelling glycoside derived from
tropical plant, - is used for improving the taste
of sweets.
The seeds contain glycoside, hot tasted, is used
for mustard preparation.
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• Before you start the chemistry course
• Be familar with chemistry and stereochemistry of
  mono-, di-, and poly-saccharides, and know the
  terminology used to designate them,
• Know its structures including derivatives of
  monosaccharides,
• Know linkages involved
• in di-, and poly-saccharides binding,
• Before you start laboratory classes
• You should be familiar with given lectures.

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