Glycolysis Overview

Overview

This lecture explains the process of glycolysis, including its steps, enzymes, phases, and the key molecules involved in energy production from glucose.

Introduction to Glycolysis

• Glycolysis means glucose (glyco) splitting (lysis).
• Occurs in the cell cytoplasm (cytosol).
• Converts one glucose molecule into two pyruvate molecules.
• Generates a net of 2 ATP and 2 NADH per glucose.
• Does not require oxygen; known as an anaerobic process.

Phases of Glycolysis

• Energy Consumption Phase: ATP is consumed in the initial steps.
• Splitting and Rearrangement Phase: Six-carbon sugar splits into two three-carbon molecules.
• Energy Payoff Phase: ATP and NADH are generated.

Detailed Steps and Enzymes

• Step 1: Glucose phosphorylated by hexokinase (uses ATP) to form glucose-6-phosphate.
• Step 2: Glucose-6-phosphate isomerized to fructose-6-phosphate by phosphoglucose isomerase.
• Step 3: Fructose-6-phosphate phosphorylated by phosphofructokinase (uses ATP) to form fructose-1,6-bisphosphate.
• Step 4: Fructose-1,6-bisphosphate split into dihydroxyacetone phosphate (DHAP) and glyceraldehyde-3-phosphate (G3P) by aldolase.
• Step 5: DHAP converted to G3P by triose phosphate isomerase (now 2 G3P per glucose).
• Step 6: G3P oxidized and phosphorylated by glyceraldehyde-3-phosphate dehydrogenase (forms NADH).
• Step 7: 1,3-bisphosphoglycerate donates phosphate to ADP (makes ATP) via phosphoglycerate kinase, forming 3-phosphoglycerate.
• Step 8: 3-phosphoglycerate converted to 2-phosphoglycerate by phosphoglycerate mutase.
• Step 9: 2-phosphoglycerate dehydrated by enolase to form phosphoenolpyruvate (PEP).
• Step 10: PEP donates phosphate to ADP (makes ATP) via pyruvate kinase, forming pyruvate.

Key Terms & Definitions

• Glycolysis — Breakdown of glucose to pyruvate with ATP and NADH production.
• Phosphorylation — Addition of a phosphate group to a molecule.
• Isomerization — Conversion of a molecule into its isomer.
• Aldolase — Enzyme splitting fructose-1,6-bisphosphate.
• Dehydrogenation — Removal of hydrogen (electrons) usually accepted by NAD+.
• Anaerobic — Metabolic processes not requiring oxygen.

Action Items / Next Steps

• Memorize the 10 enzymes of glycolysis and their specific steps.
• Practice recalling the three phases and their features.
• Review any mnemonic devices or songs to remember substrates and steps.