01/12/2026
1. Glucose → Fructose → Pyruvate
This is glycolysis — the breakdown of glucose into pyruvate for quick energy.
Example: Eat bread, glucose enters your cells, and is converted to pyruvate to start producing ATP.
2. Pyruvate → Acetyl-CoA → TCA Cycle
When oxygen’s available, pyruvate becomes Acetyl-CoA and runs through the TCA (Krebs) cycle for sustained energy.
Example: A post-lunch walk taps into this aerobic pathway.
3. TCA products → NADH → Electron Transport Chain → ATP
The TCA cycle generates NADH, which powers the electron transport chain to make ATP — your cellular energy currency.
Example: Your brain uses that ATP to keep you sharp while studying.
4. Glucose-6-Phosphate → Pentose Phosphate Pathway → NADPH + Ribose
This detour from glucose creates NADPH (for antioxidant defense) and ribose (for DNA/RNA synthesis).
Example: Immune cells use NADPH to neutralize pathogens.
5. Pyruvate → Lactate
In low-oxygen conditions, pyruvate shifts to lactate.
6. Pyruvate → Oxaloacetate → Glucose)
During fasting, pyruvate is turned into oxaloacetate, then glucose, to maintain blood sugar.
Example: After 10+ hours without food, your liver makes glucose for your brain.
7. Acetyl-CoA → Fatty Acids → Triglycerides
Excess energy is stored as fat.
Example: Too many sweets? Your body parks the surplus as belly fat.
8. Fatty Acids → Beta-Oxidation → Acetyl-CoA → TCA
When carbs run low, fat becomes your fuel.
Example: After 14 hours of intermittent fasting, fat breakdown kicks in.
9. Amino Acids → Pyruvate or Acetyl-CoA or TCA)
Amino acids can feed into different energy pathways, depending on type.
Example: In prolonged starvation, muscle protein is converted into energy intermediates.
