27. Heteropolysaccharides
• Heteroglycans
• Polysaccharides composed of different type of sugars or their
derivatives.
1) Mucopolysaccharides :
Repeating units of amino sugars
more commonly known as Glycosaminoglycans
(GAG).
Ground substance of collagen, elastin.
Eg. Hyaluronic acid, chondratin sulphate, heparin, keratan
sulphate.
28. 2 ) Glycoproteins :
Several proteins are covalently bonded to
carbohydrates.
The carbohydrate content varies from 1 to 90 %.
They are widely distributed, and act as enzymes,
hormones, transport proteins.
30. Glucose?????
Glucose acts as the central molecule in carbohydrate
metabolism as :
- Instant source of energy
- Easily synthesized
- Stored as glycogen in body
32. Takes place in all cells of the body but mainly in liver
and muscles.
Enzymes are present in cytosomal fraction of the cell.
Can occur in Anaerobic : lactate
Aerobic : pyruvate
Major pathway of ATP synthesis for tissues lacking
mitochondria eg. Erythrocytes, cornea.
33. Glycolysis
3 phases :
1) Energy investment phase or priming phase
2) Splitting phase
3) Energy generation phase
37. Glycolysis: Generation of ATP
Under anaerobic conditions: 2 ATP are synthesized
Under aerobic conditions : 6ATP are synthesized
38. Pyruvate to Acetyl CoA
Pyruvate is converted to acetyl CoA by oxidative
decarboxylation.
Irreversible reaction ,catalysed by multienzyme
complex pyruvate dehydrogenase complex(PDH), found
only in mitochondrion.
It requires 5 cofactors:
Thymine pyrophosphate
lipoamide
FAD
coenzyme A
NAD+
6 ATP are produced in this
step.
39. Citric Acid Cycle: ( Krebs cycle or
Tricarboxylic acid-TCA cycle)
Sir Hans Krebs (1900−1981) .
He was awarded the Nobel Prize in
Medicine in 1953.
40. Citric Acid Cycle
Malate
dehydrogenase
Citrate synthetase
Step I- Condensation
reaction
Step II isomerisation
Aconitase
fumarase
Succinate
dehydrogenase
α-ketoglutarate
dehydrogenase
Succinate
complex.
thiokinase
Isocitrate
Step IV
dehydrogenase
– oxidative
decarboxylation
Five cofactors:
Thymine
pyrophosphate
Lipoamide
NAD+
FAD
CoA
41. Reaction catalysed
by
Method of production
of ATP
No. of ATP
produced
Isocitrate
dehydrogenase
Oxidation of 2 NADH
6
α ketoglutarate
dehydrogenase
Oxidation of 2 NADH
6
Succinate thiokinase
Oxidation at substrate level
2
Succinate
dehydrogenase
Oxidation of FADH2
4
Malate dehydrogenase Oxidation of 2 NADH
TOTAL
6
24
42. Total number of ATP generated from oxidation of 1
molecule of glucose:
Glycolysis
8 ATP
Conversion of pyruvate to
Acetyl CoA
6 ATP
Citric acid cycle
24 ATP
TOTAL
38 ATP
43. Relation With Periodontium
• TCA cycle is ACTIVE in basal and parabasal
layers
• Glucose – 6- phosphatase activity is more
towards surface
• Glycogen concentration is inversily related to
degree of keratinization and inflammation
• Laminin (glycoprotien)- basal lamina
44. • The enzymes of the glycolytic cycle:
phosphohexoisomerase, aldolase,
phosphoglycerokinase and glucose-6-phosphatase
were determined in the gingiva, periosteum and
periodontium of the mandibular incisor region in the
guinea pig and compared with their activities in the
liver, kidneys, adrenals, pituitary and testes of the
same animal.
{E.H. Charreau, J.A. Kofoed, A.B. Houssay: Enzymes of
glycolytic cycle in periodontal tissues of the guinea pig.
Archives of Oral Biology}
45. Gluconeogenesis
Synthesis of glucose from non-carbohydrate
compounds is known as gluconeogenesis.
The major substrates/ precursors are:
Lactate
Pyruvate
Glucogenic aminoacids
Propionate
Glycerol.
46. 1.
Intake of high protein diet
2.
During muscular exercise, large amounts of lactic acids
is produced, liver picks up the Lactic acid and converts
into glucose & glycogen via Cori cycle.
3.
During starvation, tissue proteins are broken down and
amino acids are utilized for gluconeogenesis.
47. Regulation of Gluconeogenesis
- Glucagon by α-cells
- Availability of substrates
- Alcohol consumption interferes -
hypoglycemia
48. Hexose Monophosphate shunt
(HMP shunt)
Also known as Pentose phosphate pathway
Phosphogluconate pathway
Alternative pathway to Glycolysis and TCA cycle for
oxidation of glucose.
Enzymes located in cytosol
53. Glycogenolysis
• Degradation of stored glycogen in liver and muscle to
glucose.
• Site- cytosol.
• Glycogen is degraded by breaking α-1,4 and β-1,6
glycosidic bonds.
54.
55.
56. Glycogen Storage Diseases
Enzyme defect
Type I: von Gierke’s disease
Glucose-6-phosphate
Type II: Pompe’s disease
Lysosomal α-1,4 glucosidase
Type III: Cori’s disease or limit
dextrinosis
Amylo α-1,6 glucosidase (debranching
enzyme)
Type IV: Andersen’s disease or
amylopectinosis
Glucosyl 4-6 transferase (branching enzyme)
Type V: McArdle’s syndrome
Muscle glycogen phosphorylase
Type VI: Her’s disease
Liver glycogen phosphorylase
Type VII: Tauri’s disease
Muscle and erythrocyte phosphofructokinase 1
58. Digestion
Occurs largely in the intestine and briefly in mouth.
In mouth : During mastication, salivary amylase acts on
starch cleaves α-1,4-glycosidic bonds.
In small intestine : Pancreatic α amylase acts on starch
(specially on α-1,4-glycosidic bonds) to form
oligosaccharides and disaccharides (maltose, isomaltose)
59. Absorption
Glucose accounts for 80% of total monosaccharides
Absorption sites :
Duodenum and upper jejunum.
Rate of absorption
Galactose > glucose > fructose
60. Selective permeability :
Facilitates absorption of smaller molecules
Prevents bigger molecules from being absorbed.
Active transport:
Membrane transport system involving active absorption by
conc. gradient.
This transport is facilitated along with Na+ .(glucoseNa+ symport)
This process requires metabolic energy which is provided
by the Na+-K+ ATPase enzyme.
61.
62. Interaction Between Carbohydrates
And Dental Plaque :
Sucrose in the food causes plaque to be copiously
produced and of gelatinous nature with much
extracellular polysaccharide matrix.
Extracellular polysaccharides help plaque adhere to
smooth surfaces and prevent the buffering action of
saliva.
63. References
•
Carranza’s Clinical Periodontology 10th Edition
•
Essentials Of Biochemistry By U Satyanarayana 2nd Edition.
•
Harper’s Biochemistry 24th Edition
•
Fundamentals Of Biochemistry By Ambika Shanmugan 6th
Edition
•
Basic And Dental Applied Biochemistry 2nd Edition RAD
Williams.
•
Organic And Biochemistry For Today Spencer L. Seager /
Michael R. Slabaugh 4th Edition
64. References
•E.H. Charreau, J.A. Kofoed, A.B. Houssay: Enzymes of
glycolytic cycle in periodontal tissues of the guinea pig.
Archives of Oral Biology:Volume 11, Issue 7, July 1966, Pages
709–715.