Presentation on theme: "Introduction of Glucose Metabolism"— Presentation transcript:
1 Introduction of Glucose Metabolism Lecture-2Glycolysis
2 GlycolysisGlycolysis 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.
3 End 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)
5 Glycolysis Glucose (6C) 2 Pyruvate (3C) 2 ATP 4 ADP 2 ADP 4 ATP 2 NAD 2 NADH+ H+2 Pyruvate (3C)
6 End 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
8 Key enzymes in glycolysis Steps catalyzedBykey enzymesONE WAY REACTIONS123
9 Energy 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.
10 Energy 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
11 GLUCOSE 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
12 ENERGY 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
13 Regulation 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)
14 Example of Covalent Modification (short-term regulation)
15 Long-term Regulation of glycolysis Induction & Repression of enzymes synthesis Insulin: InductionGlucagon: Repression
16 Genetic 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.