Embed Size (px)
Citation preview
CH2OH
C=O
CHOH)n(
CH2OH
C
O
H
CHOH)n
CH2OH
(
CARBOHYDRATES-:
Functions-energetical function – source of energy for the cellular reactionsprotective and mechanical functionscoenzymatic functionhydroosmoticSome monosaccharides form part of nucleotides A lot of representatives of carbohydrates participate in-anticoagulation of blood, in the immune processes, in cell growth, biological recognition processes.
Carbohydrates are compounds which contains-: no less then 2 hydroxil
and one carbonil – Aldehyd or ketone
Classificatiion:- Mono s a cc harid s : -In depending of functional group of molecule: A-
Aldoze – glyceraldehyde, ribose, glucose, galactoseKetoze – dioxyacetone, ribulose, xilulose, fructose
Aldoses ketosesB-In depending of the number of carbon atoms in molecule:
trioze – glyceraldehyde, dioxyacetonetetrozepentoze – ribobe, ribuloze, xiluloze ,hexoze - glucoze, galactoze, manoze, fructoze,heptoze – sedoheptuloze.
Oligo s a c haride s -: are formed from 2 till 10 monosaccharides: disaccharides: sucrose, lactoze, maltoze;trisaccharides;
tetrasaccharidespentasaccharides
Poli s a cc haride s : -homopolysaccharides – are formed from the same monomeres: glycogen, starch, celuloze
D-glucose L-glucose
C H
O
C OHH
C HHO
CH2OH
C OHH
C OHH
C H
O
CH2OH
C OHH
C HHO
C HHO
C HHO
C H
O
C OHH
CH2OH
C OHH
H C OH
C HHO
C H
O
CH2OH
C OHH
H C OHC HHO
C H
O
C OHH
CH2OH
C OHH
C H
O
C H H
CH2OH
C OHH
H C OH
D-Ribose D-Xylose D-Arabinose D-Dezoxiribose
Heteropolysaccharides – from different monomeres – glucoz-aminoglicanes .
Stereoisomeria of monosaccharides-:
Monosaccharides contain one or more chiralic carbon atoms .
Stereoisomeria of glucose:- Pentoses-:
Hexoses-:
Pyranose cycle - a-D-Glucopyranose b-D- Glucopyranose
HO
CH2OH
HOH
H
H
OH
H
OO
H OH
H
OH
H
H
OH
HH
CH2OH
O
Furanose cycle -:
Oligosaccharides:- Maltose Lactose Sucrose
Maltose-
Lactose:- known as a milk sugar … consists of b-D-galactose and a-D-glucose, joined through a b-(1-4)-glycoside linkage.
Non-reducing disaccharides Sucrose:- Sucrose is a disaccharide that contains b-D-fructose and a-D-glucose, joined by a glycoside bond between carbons.
Polysaccharides-:Starch is the reserve carbohydrate that are stored by plants in roots, tubers and seeds.Glycogen is the reserve carbohydrate of animals, and a relatively small amount is stored in the liver and muscles.Starch can be:- is amylose (20%), that is water-soluble. amylopectin (80%), is water-insoluble.
O
CH2OH
HH
OH
H
H
OH
O
O
CH2OH
HH
OH
H
H
OH
H
O
O
CH2OH
HH
OH
H
H
OH
H
O
O
CH2OH
HH
OH
H
H
OH
O
O
CH2OH
HH
OH
H
H
OH
H
O
OH
H
H
OH
HH
CH2OH
O
H
O
O
CH2OH
HH
OH
H
H
OH
H
O
OH
H
H
OH
HH
CH2OH
O
H
O
Amylose-:
Amylopectin-:
Glycogen:- Glycogen is also a polymer of glucose residues linked mainly by a(1,4) glycosidic linkages.Molecule of glycogen is considerable bigger then the molecule of amylopectin.
Cellulose-:Cellulose is the structural material of plants and is the most abundant organic substance found in nature. by b-(1,4)glycosidic linkages.
Digestion
and absorption of carbohydrates -:
The digestion of starch begins with salivary amylase, but this activity is much less important than that of pancreatic amylase in the small intestine.
Amylase hydrolyzes starch, with the primary end products being maltose, maltotriose .
amylase digestion are hydrolyzed into their component monosaccharides by enzymes maltase, sucrase, isomaltase and lactase.
maltase cleaves maltose into two molecules of glucose .lactase cleaves lactose into a glucose and a galactose .sucrase cleaves sucrose into a glucose and a fructose.
Monosaccharide absorption occurs primarily in the upper small intestine.Only D-glucose and D-galactose are actively absorbed in the human small intestine. The sodium dependent glucose transporter, SGLT1.
Glucose is pumped out of the enterocyte into the intracellular space by the glucose transporter 2 (GLUT2).D-fructose is not actively absorbed, but is taken up by facilitated transport by the glucose transporter 5 (GLUT5).
Glycogen Synthesis: Synthesis of glycogen from glucose is carried out the enzyme glycogen synthase. This enzyme utilizes UDP-glucose as one substrate and the non-reducing end of glycogen as another.
Branching enzyme:- A branching enzyme transfers a segment from the end of a glycogen chain to the C6 hydroxyl of a glucose residue of glycogen to yield a branch with an a(1,6) linkage.
Glycogen catabolism (glycogenolysis) -:Degradation of glycogen, termed glycogenolysis, occurs through the action of enzyme glycogen phosphorylase.
The product of this reaction is glucose-1-phosphate .Glycogen Phosphorylase catalyzes phosphorolytic cleavage of the a(1,4).
glucose-1-phosphate as the reaction product.
Phosphoglucomutase:- The glucose-1-phosphate produced by the action of phosphorylase is converted to glucose-6-phosphate by phosphoglucomutase.
Phosphoglucomutase catalyzes the reversible reaction -:
The liver enzyme Glucose-6-phosphatase catalyzes the following reaction, essential to the liver's role in maintaining blood glucose: Glucose-6-phosphate + H2O à glucose + Pi.
