The breaking of C-C bonds of complex compounds through oxidation within cells, leading to the release of considerable amount of energy (stored as ATP).
Complete combustion of glucose yields CO₂ and H₂O.
Occurs in the cytoplasm of all living organisms. Anaerobic process.
Partial oxidation of Glucose (6C) into two molecules of Pyruvic acid (3C). Net gain: 2 ATP and 2 NADH.
Occurs under anaerobic conditions. Pyruvic acid is converted to either Ethanol and CO₂ (Alcoholic fermentation - Yeast) or Lactic acid (Lactic acid fermentation - Muscle cells, some bacteria). Yield is very low (only 2 ATP).
Takes place within mitochondria. Complete oxidation of organic substances.
1. Link Reaction: Pyruvic acid is converted to Acetyl CoA in the mitochondrial matrix. Releases CO₂ and NADH.
2. Krebs Cycle (TCA Cycle): Operates in the mitochondrial matrix. Complete oxidation of Acetyl CoA. Yields NADH, FADH₂, ATP, and CO₂.
3. Electron Transport System (ETS): Occurs in the inner mitochondrial membrane. NADH and FADH₂ are oxidized, electrons are passed to O₂ (terminal acceptor) to form H₂O. Drives synthesis of ATP (Oxidative phosphorylation).
RQ for Carbohydrates = 1. RQ for Fats = ~0.7. RQ for Proteins = ~0.9.