Glycolysis (CHEM 141: Biochemistry II) PDF

Unit III Glycolysis CHEM 141: Biochemistry II KFL ‘25 Topic Outline A. Glycolysis E. Fates of Pyruvate B. Two Phases of Glycolysis Aerobic metabolism Preparatory Phase Anaerobic metabolism...

Unit III Glycolysis CHEM 141: Biochemistry II KFL ‘25 Topic Outline A. Glycolysis E. Fates of Pyruvate B. Two Phases of Glycolysis Aerobic metabolism Preparatory Phase Anaerobic metabolism Payoff Phase F. Entry of Other Metabolites in C. Glycolysis Steps Glycolysis 10 steps of glycolysis Fructose ATP production Mannose Summary Galactose D. Regulation of Glycolysis Glycerol G. High Rate of Glycolysis in Tumors 2 Glycolysis “Living organisms, like machines, conform to the law of conservation of energy, and must pay for all their activities in the currency of catabolism.” - Ernest Baldwin Dynamic Aspects of Biochemistry (1952) 3 Glycolysis 4 Glycolysis 5 Glycolysis also known as the Embden-Meyerhof pathway: – the stepwise degradation of glucose (and other simple sugars). a series of reactions in the cytoplasm that converts glucose (C6) to two molecules of pyruvate (a C3 carboxylate), along with ATP and NADH production. An anaerobic process; each step takes place without O2, which can provide 2 molecules of ATP per glucose molecule. 6 Two Phases of Glycolysis 7 Glycolysis Steps ❶ Hexokinase traps glucose in the cell and begins glycolysis - The First Priming Reaction 8 Glycolysis Steps “priming reaction” - phosphorylation activates glucose phosphorylation keeps the substrate in the cell 9 Glycolysis Steps ❷ Phosphoglucoisomerase Catalyzes the Isomerization of Glucose-6-Phosphate 10 Glycolysis Steps ❸ ATP Drives a Second Phosphorylation by Phosphofructokinase — The Second Priming Reaction 11 Glycolysis Steps ❹ Cleavage by Fructose Bisphosphate Aldolase Creates Two 3-Carbon Intermediates 12 Glycolysis Steps ❺ Triose Phosphate Isomerase Completes the First Phase of Glycolysis 13 Glycolysis Steps ❻ Glyceraldehyde-3-Phosphate Dehydrogenase Creates a High-Energy Intermediate 14 Glycolysis Steps ❼ Phosphoglycerate Kinase Is the Break-Even Reaction 15 Glycolysis Steps ❽ Phosphoglycerate Mutase Catalyzes a Phosphoryl Transfer 16 Glycolysis Steps ❾ Dehydration by Enolase Creates PEP 17 Glycolysis Steps ❿ Pyruvate Kinase Yields More ATP 18 Glycolysis Steps ATP Production and Consumption 19 Glycolysis Steps Glucose to pyruvate (exergonic): Formation of ATP from ADP and Pi (endergonic): Overall Reaction: 20 Glycolysis Summary 21 Glycolysis Summary 22 Glycolysis Summary 23  Exercise 1 │ Glycolysis Intermediates Specify the number of carbon atoms present and the number of phosphate groups present in each of the following glycolysis intermediates. a. Glucose 6-phosphate b. Fructose 1,6-bisphosphate c. Glyceraldehyde 3-phosphate d. 3-Phosphoglycerate (a) (b) (c) Answers: a. C6-1P; b. C6-2P; c. C3-1P; d. C3-1P 24  Exercise 2 │ Glycolysis Steps Indicate at what step in the glycolysis pathway each of the following events occurs. a. Second formation of ATP occurs. b. Second “energy-rich” compound is produced. c. ATP is converted to ADP for the second time. d. A dehydration reaction occurs. (b) (a) (c) Answers: a. Step 10; b. Step 9; c. Step 3; d. Step 9 25  Exercise 3 │ Glycolysis Enzymes Relate the names and functions of the following glycolytic enzymes to steps in the process of glycolysis. a. Hexokinase b. Pyruvate kinase c. Glyceraldehyde 3-phosphate dehydrogenase d. Phosphoglycerokinase (b) (a) (c) Answers: a. Step 1; b. Step 10; c. Step 6; d. Step 7 26 Regulation of Glycolysis 27 Regulation of Glycolysis 28 Regulation of Glycolysis Enzyme Activator Inhibitor Hexokinase - Glucose-6-phosphate, ATP (Step 1) Phosphofructokinase-1 Fructose-2,6-bisphosphate, Citrate, ATP (Step 3) AMP Pyruvate kinase Fructose-1,6-bisphosphate, ATP, Acetyl-CoA, Alanine (Step 10) AMP All the above enzymes are allosteric. 29 Regulation of Glycolysis Free-Energy Changes of Glycolytic Reactions in Erythrocytes 30