Glycolysis and Gluconeogenesis Student Notes PDF

Overview – phases • Glycolysis can be divided into two main phases: Glucose Phase I: Preparative Phase ATP ATP Fructose 1,6-bisphosphate DHAP Phase II: ATP - generating phase Glyceraldehyde-3-P 2 NADH + 2 H+ 2 ATP 2 ATP 2 Pyruvate Glycolysis Overview Overview – Reactions 1 à 3 Glycolysis –...

Overview – phases • Glycolysis can be divided into two main phases: Glucose Phase I: Preparative Phase ATP ATP Fructose 1,6-bisphosphate DHAP Phase II: ATP - generating phase Glyceraldehyde-3-P 2 NADH + 2 H+ 2 ATP 2 ATP 2 Pyruvate Glycolysis Overview Overview – Reactions 1 à 3 Glycolysis – Reaction 1 • Enzyme: Hexokinase/ Glucokinase !G0’ = -16.7 kJ/mol • Q: Glucose is now trapped in the cell, why? What is the role of Mg2+ cofactor? Glycolysis – Reaction 2 • Enzyme: Phosphoglucose isomerase H2C - OH 1 !G0’ = +1.67 kJ/mol • Since the !G0’ is positive, how does the reaction proceed in the forward direction? Glycolysis – Reaction 3 • Enzyme: Phosphofructokinase 1 (PFK-1) !G0’ = -14.2 kJ/mol • Rate-limiting & committing step of glycolysis • Most important regulated reaction § More to come later Glycolysis – Reaction 3 continued • After the addition of the second phosphoryl group the straight chain form is favoured Overview – Reactions 4 & 5 Glycolysis – Reaction 4 • Enzyme: Aldolase + !G0’ = +23.9 kJ/mol Glycolysis – Reaction 5 • Enzyme: Triose phosphate isomerase !G0’ = +7.56 kJ/mol • What would be the effect on glycolysis if triose phosphate isomerase was not present/ able to function? Overview – Reactions 6 & 7 Glycolysis – Reaction 6 • Enzyme: Glyceraldehyde-3-phosphate dehydrogenase Glycolysis - Reaction 7 • Enzyme: Phosphoglycerate kinase !G0 = -18.8 kJ/mol Overview – Reactions 8 à 10 Glycolysis – Reaction 8 • Enzyme: Phosphoglycerate mutase !G0 = 4.4 kJ/mol Glycolysis – Reaction 9 • Enzyme: Enolase !G0 = +7.5 kJ/mol Glycolysis – Reaction 10 • Enzyme: Pyruvate kinase !G0 = -31.4 kJ/mol Review – phases • Glycolysis can be divided into two main phases: Glucose Phase I: Preparative Phase ATP ATP Fructose 1,6-bisphosphate DHAP Phase II: ATP - generating phase Glyceraldehyde-3-P 2 NADH + 2 H+ 2 ATP 2 ATP 2 Pyruvate Review – direct energy • 2 ATP are required during the preparatory phase of glycolysis • 4 ATP are created during the generating phase of glycolysis § Substrate level phosphorylation • Net of 2 ATP/ glucose molecule Glucose ATP ATP Fructose 1,6-bisphosphate DHAP Glyceraldehyde-3-P 2 NADH + 2 H+ 2 ATP 2 ATP 2 Pyruvate Review – indirect energy • 2 NADH is generated per glucose molecule § Where does the NADH go? Glucose ATP ATP Fructose 1,6-bisphosphate DHAP • Under aerobic conditions, where does pyruvate go next? Glyceraldehyde-3-P 2 NADH + 2 H+ 2 ATP 2 ATP 2 Pyruvate Summary – irreversible reactions • There were three irreversible reactions: § 1) Glucose à Glucose-6-phosphate § 3) Fructose-6-phosphate à Fructose 1,6-bisphosphate § 10) Phosphoenolpyruvate à pyruvate • Preview: § These reactions are the three main regulated steps of glycolysis • Much more to come later in the term