VITL

Master metabolism with 9 steps/arrows Here’s my shortcut to remembering it in just 9️⃣ arrows: 1️⃣ Glu → Fru → Pyr (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. 2️⃣ Pyr → ACoA → TCA (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. 3️⃣ TCA → NADH → ETC → ATP (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. 4️⃣ G6P ↔ PPP → NADPH + Ribose (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. 5️⃣ Pyr → Lac (Pyruvate → Lactate) In low-oxygen conditions, pyruvate shifts to lactate. 6️⃣ Pyr → OAA → Gluconeogenesis (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. 7️⃣ ACoA → FAs → TAGs (Acetyl-CoA → Fatty Acids → Triglycerides) Excess energy is stored as fat. 💡 Example: Too many sweets? Your body parks the surplus as belly fat. 8️⃣ FAs → β-ox → ACoA → TCA (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. 9️⃣ AAs → Pyr / ACoA / TCA (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.