Glycolysis: The Core Pathway
Glycolysis is the anaerobic breakdown of glucose into two molecules of pyruvate, generating a net gain of 2 ATP and 2 NADH.
| Key Regulatory Steps | Enzyme | Regulation Notes |
|---|---|---|
| Step 1 (Investment) | Hexokinase / Glucokinase | Inhibited by Glucose-6-Phosphate. |
| Step 3 (Rate-Limiting) | Phosphofructokinase-1 (PFK-1) | Activated: AMP, Fructose-2,6-bisphosphate. Inhibited: ATP, Citrate. |
| Step 10 (Yield) | Pyruvate Kinase | Activated by Fructose-1,6-bisphosphate; Inhibited by ATP and Alanine. |
High-Yield Core Realities:
- Energy Balance: The regulatory master, Phosphofructokinase-1 (PFK-1), ensures the cell doesn’t burn glucose when ATP levels are already high.
- Anaerobic Fate: In the absence of oxygen, pyruvate is converted to lactate by Lactate Dehydrogenase to regenerate NAD+ for continued glycolysis.
- Clinical Correlate: RBCs lack mitochondria and rely exclusively on glycolysis, making them dependent on this pathway for ATP to maintain the Na+/K+ pump.