Glycolysis Lecture Notes

34 vocabulary flashcards covering enzymes, intermediates, regulation, and energetics of glycolysis.

Glycolysis

degrades one glucose in a series of enzyme-catalyzed reactions to yield two pyruvate while producing a net 2 ATP and 2 NADH.

Preparatory Phase

The first half of glycolysis in which 2 ATP are invested to convert glucose to F1,6-BP, then to 2 three-C molecules: Ga3P and DHAP

Payoff Phase

The second half of glycolysis where oxidation and substrate-level phosphorylation generate 2 ATP, 2 NADH, and 2 pyruvate.

Phosphofructokinase-1 (PFK-1) regulation

allosterically regulated by ADP and AMP (more active) and ATP (less active); F2,6-BP (more active) by increasing its affinity for F6P, F2,6BP is produced by PFK-2

PFK-2

Bifunctional enzyme that synthesizes and degrades F-2,6-BP, thereby toggling between glycolysis and gluconeogenesis.

Substrate-Level Phosphorylation

ATP formation by direct transfer of a phosphoryl group from a high-energy intermediate to ADP.

Net Yield of Glycolysis

Per glucose: 2 pyruvate + 2 ATP (net) + 2 NADH + 2 H₂O + 2 H⁺.

Phosphorylated Intermediates

Nine glycolytic compounds bearing phosphate groups that keep metabolites in the cell, lower activation energy, and enable energy capture.

Metabolic Fates of Pyruvate

Can enter the citric acid cycle (aerobic) or be reduced to lactate or ethanol (anaerobic) to regenerate NAD⁺.

Aerobic Oxidation

Conversion of pyruvate to acetyl-CoA and CO₂, followed by the citric acid cycle and oxidative phosphorylation.

Anaerobic Reduction

Conversion of pyruvate to lactate or ethanol, allowing glycolysis to continue without oxygen by regenerating NAD⁺.

Entry of Fructose into Glycolysis

fructose can be directly converted to F6P by hexokinase, entering here; F1P (via F1Paldoase) or glycerol-3P (via glycerol phosphate dehydrogenase) can be converted into DHAP and then Ga3P

glycolysis step 1: phosphorylation of glucose

hexokinase phosphorylates glucose at C-6 using ATP and Mg2+, yielding G6P (irreversible)

glycolysis step 2: conversion of G6P to F6P

Phosphohexose isomerase catalyzes isomerization of G6P to F6P (reversible)

glycolysis step 3: phosphorylation of F6P to F1,6BP

Phosphofructokinase-1 (PFK-1) catalyzes the transfer of a P group from ATP to F6P to yield F1,6BP (irreversible, committed step)

glycolysis step 4: cleavage of F1,6BP

Fructose 1,6-bisphosphate aldolase catalyzes reverse aldol condensation, cleaving F1,6BP into Ga3P (from C 4-6) and DHAP (from C 1-3), which can interconvert via triose phosphate isomerase (reversible)

glycolysis step 5: oxidation of Ga3P into 1,3BPG

Glyceraldehyde 3-phosphate dehydrogenase catalyzes the oxidation using NAD+

glycolysis step 6: P transfer from 1,3-BPG to ADP

Phosphoglycerate kinase transfers P group from carboxyl group of 1,3-BPG to ADP, generating ATP and 3-phosphoglycerate (reversible, substrate-level phosphorylation)

glycolysis step 7: conversion of 3-phosphoglycerate to 2-phosphoglycerate

Phosphoglycerate mutase catalyzes P shift from C-3 to C-2 (reversible)

glycolysis step 8: dehydration of 2-phosphoglycerate to phosphoenolpyruvate

enolase removes water from 2-phosphoglycerate to yield PEP

glycolysis step 9: transfer of P group from PEP to ADP

Pyruvate kinase catalyzes the transfer of the P group from PEP to ADP, yielding pyruvate and ATP (irreversible, substrate-level phosphorylation)