Carbohydrates and glycolytic pathway.. periodontics
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Carbohydrates and glycolytic pathway.. periodontics Carbohydrates and glycolytic pathway.. periodontics Presentation Transcript

  • Good morning…
  • Presented By Dr. Guru Ram (I Year Post Graduate) Department Of Periodontics
  • Contents • • • • Introduction Functions Classification Metabolism • Glycolysis • Krebs cycle • Gluconeogenesis • Hexose MonoPhosphate shunt (HMP shunt) • Glucogenesis and Glycogenolysis • Carbohydrates Related To Dental Plaque
  • Introduction
  • Classification Monosaccharides Disaccharides Carbohydrates oligosaccharides Hetero Polysaccharides Homo
  • Monosaccharides Monosaccharides Number of Catoms Functional group
  • Monosaccharides Physical properties
  • Stereoisomerism CHO CHO H C OH HO L-glyceraldehyde CHO H C OH CH2OH D-glyceraldehyde H CH2OH CH2OH D-glyceraldehyde C CHO HO C H CH2OH L-glyceraldehyde
  • Optical Activity
  • • Levorotatory • Dextrorotatory • Racemic mixture
  • Epimers
  • Chemical Properties
  • Furanose form of fructose
  • • β-D-Ribose • β-D-Deoxyribose • β-D- Galactose • β-D- Glucose • β-D-Fructose
  • Disaccharides
  • Disaccharides Reducing Non Reducing
  • Reducing Sugars • Maltose • Lactose
  • Non Reducing Sugars • Sucrose • Trehalose
  • Oligosaccharides
  • Raffinose
  • Polysaccharides
  • Polysaccharides Homo Hetero
  • Homopolysaccharides • Starch Amylose Amylopectin • Glycogen • Cellulose
  • Starch- amylose
  • Starch- amylopectin
  • Glycogen
  • 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.
  • 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.
  • Metabolism Of Carbohydrates • Catabolism • Anabolism
  • Glucose????? Glucose acts as the central molecule in carbohydrate metabolism as : - Instant source of energy - Easily synthesized - Stored as glycogen in body
  • Glycolysis (EmbdenMayerhof-Parnas pathway) {Glycos- sugars, lysis-dissolution}
  • 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.
  • Glycolysis 3 phases : 1) Energy investment phase or priming phase 2) Splitting phase 3) Energy generation phase
  • Energy investment phase
  • Splitting phase
  • Energy Generation Phase
  • Glycolysis: Generation of ATP  Under anaerobic conditions: 2 ATP are synthesized  Under aerobic conditions : 6ATP are synthesized
  • 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.
  • 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.
  • 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
  • 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
  • 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
  • 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
  • • 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}
  • Gluconeogenesis Synthesis of glucose from non-carbohydrate compounds is known as gluconeogenesis. The major substrates/ precursors are: Lactate Pyruvate Glucogenic aminoacids Propionate Glycerol.
  • 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.
  • Regulation of Gluconeogenesis - Glucagon by α-cells - Availability of substrates - Alcohol consumption interferes - hypoglycemia
  • 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
  • Oxidative phase
  • Non oxidative phase Ribulose- 5 - phosphate TPP and Transketolase Glyceraldehyde-3 phosphate Reversal of glycolysis Fructose- 6 phosphate
  • Glycogenesis
  • 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.
  • 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
  • Digestion and Absorption
  • 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)
  • Absorption Glucose accounts for 80% of total monosaccharides Absorption sites : Duodenum and upper jejunum. Rate of absorption Galactose > glucose > fructose
  • 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.
  • 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.
  • 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
  • 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.
  • Thank You…