Presentation on theme: "Introduction of Glucose Metabolism"— Presentation transcript:
1Introduction of Glucose Metabolism Lecture-2Glycolysis
2GlycolysisGlycolysis is the breakdown of glucose to: 1- Provide energy in the form of ATP (main function) 2- Provide intermediates for other metabolic pathways. It occurs in cytosols of all tissues All sugars can be converted to glucose & thus can be metabolized by glycolysis.
3End products of glycolysis 1- In cells with mitochondria & an adequate supply of oxygen (Aerobic glycolysis) - Pyruvate: enters the mitochondria & is converted into acetyl CoA. Acetyl CoA enters citric acid cycle (Krebs cycle) to yield energy in the form of ATP - NADH: utilizes mitochondria & oxygen to yield energy 2- In cells with no mitochondria or adequate oxygen (or Both) (Anaerobic glycolysis) Lactate: formed from pyruvate (by utilizing NADH)
5Glycolysis Glucose (6C) 2 Pyruvate (3C) 2 ATP 4 ADP 2 ADP 4 ATP 2 NAD 2 NADH+ H+2 Pyruvate (3C)
6End products of glycolysis AEROBIC GLYCOLYSISMitochondria & OxygenNADHis an end productof aerobic glycolysisANAEROBIC GLYCOLYSISNo mitochondriaNo OxygenOr BothPyruvateis the end productof aerobic glycolysisLactateis the end productof anaerobic glycolysis
8Key enzymes in glycolysis Steps catalyzedBykey enzymesONE WAY REACTIONS123
9Energy yield from glycolysis 1- Anerobic glycolysis2 molecule of ATP for each one molecule of glucose converted to 2 molecules of lactateIt is a valuable source of energy under the following conditions1- Oxygen supply is limited as in2- Tissues with no mitochondria skeletal muscles during intensive exerciseKidney medullaRBCsLeukocytesLens & cornea cellsTestes2-Aerobic glycolysis2 moles of ATP for each one mol of glucose converted to 2 moles of pyruvate2 molecules of NADH for each molecule of glucose2 or 3 ATPs for each NADH entering electric transport chain (ETC) in mitochondria.
10Energy yield from glycolysis In anaerobic glycolysis:2 ATP for one glucose moleculeIn aerobic glycolysisGlycolysis: 2 ATP2 NADH: 2 X 3 = 6 ATPNADHPyruvate Acetyl CoA2 Pyruvate produce 2 Acetyl CoA (& 2 NADH): 2 X 3 = 6 ATP2 Acetl CoA in citric acid cycle: 2 X 12 = 24 ATP
11GLUCOSE Energy yield of aerobic glycolysis Energy yield of anaerobic glycolysisGLUCOSENet = 38 ATP / glucose moleculeNet = 2 ATP/ glucose molecule2NAD+2 ATP2 NADH= 2 X 3 = 6 ATPNo OxygenNo MitochondriaOR BOTHOxygen&Mitochondria2 Lactate2 PYRUVATE2NAD+2 NADH= 2 X 3 = 6 ATP2 ACETYL CoACITRIC ACID CYCLE= 2 X 12 = 24 ATP
12ENERGY PRODUCTION Oxidative phosphorylation & Substrate-level phosphorylation The formation of high-energy phosphate bonds by phosphorylation of ADP to ATPcoupled to the the electron transport chain (ETC) that occurs in the mitochondria.Substrate-level phosphorylation: The formation of high-energy phosphate bonds by phosphorylation of ADP to ATP (or GDP to GTP)It is coupled to cleavage of a high-energy metabolic intermediate (substrate).It may occur in cytosol or mitochondriaExample: in glycolysis ATPs are produced
13Regulation of key enzyme of glycolysis The regulation of the activity of key enzyme is conducted through:1- General: (occurs in all types of enzymes in the body)increasing substrate concentration will lead to increase activity of theenzyme2-Special regulatory mechanisms:i- Allosteric effectorsii- Covalent modificationiii. Induction/Repression of enzyme synthesis( long –term regulation)
14Example of Covalent Modification (short-term regulation)
15Long-term Regulation of glycolysis Induction & Repression of enzymes synthesis Insulin: InductionGlucagon: Repression
16Genetic defects of glycolytic enzymes Pyruvate kinase deficiencyPyruvate kinase (PK) deficiency leads to a reduced rate of glycolysis with decreased ATP production.PK deficiency effect is restricted RBCs.As RBCs has no mitochondria & so get ATP only from glycolysis.RBCs needs ATP mainly for maintaining the bio- concave flexible shape of the cell.PK deficiency leads to severe deficiency of ATP for RBCs. So, RBCs fail to maintain bi-concave shape ending in liability to be lysed (hemolysis).Excessive lysis of RBCs leads to chronic hemolytic anemia.