Cellular respiration is the set of metabolic processes by which cells convert glucose and oxygen into energy in the form of ATP, with carbon dioxide and water as byproducts. The overall, summed equation is: C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + energy (ATP) Key points and components:
- Overall equation: The reaction summarizes multiple steps that occur in different organelles and pathways, not a single reaction happening in one place.
- Main substrates and products:
- Glucose (C6H12O6) and oxygen (O2) are consumed.
- Carbon dioxide (CO2) and water (H2O) are produced.
- Net ATP is produced, along with reduced cofactors NADH and FADH2 which feed the electron transport chain to generate more ATP.
- Major stages (in order):
- Glycolysis: Occurs in the cytoplasm; glucose is split into two pyruvate molecules, generating a small amount of ATP and NADH.
- Pyruvate oxidation: Occurs in mitochondria; pyruvate is converted to acetyl-CoA, producing NADH and releasing CO2.
- Citric acid cycle (Krebs cycle): Occurs in the mitochondrial matrix; acetyl-CoA is oxidized to CO2, producing NADH, FADH2, and a small amount of ATP (or GTP).
- Oxidative phosphorylation (electron transport chain and chemiosmosis): Occurs across the inner mitochondrial membrane; NADH and FADH2 donate electrons, creating a proton gradient that drives the synthesis of the majority of ATP via ATP synthase; O2 serves as the final electron acceptor to form water.
- Aerobic vs anaerobic:
- Aerobic respiration uses oxygen and yields maximum ATP.
- In the absence of oxygen, cells can ferment to regenerate NAD+ and continue glycolysis, but energy yield is much lower.
- Common practice:
- The textbook “summary equation” emphasizes the net consumption of glucose and oxygen and the net production of carbon dioxide and water, coupled with ATP production.
If you’d like, I can tailor this to a specific level (high school, introductory college, or bioinformatics), or provide a step-by-step breakdown of each stage with the corresponding balanced reactions and where in the cell each step occurs.
