Energy Metabolism Summary and ATP Yields
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A one-glance outline of the three systems and their ATP yields — stored ATP-PC, net 2 ATP from the lactic acid system, and net 36 ATP from the aerobic system.
Detail
A brief outline of energy metabolism, as summarized in the source:
| System | Reactions / Yield |
|---|---|
| ATP-PC System / Stored Energy | ADP + Energy + P ⇌ ATP; PC + ADP ⇌ ATP |
| Lactic Acid System / Net 2 ATP | Glycogen/Glucose → Pyruvic Acid ⇌ Lactic Acid |
| Aerobic Energy System / Net 36 ATP | Krebs Cycle + Electron Transport System (source's classic figure — see Oxygen (Aerobic) Energy System for the 2026-revised ~30-32 ATP estimate) |
The diagram links Glycogen/Glucose → Pyruvic Acid → Lactic Acid (anaerobic branch), with pyruvic acid instead feeding the Krebs Cycle and Electron Transport System when oxygen is available (aerobic branch). The phosphagen reactions (ADP + P + Energy → ATP) sit upstream as stored, immediate energy.
Key facts
- ATP-PC system: stored energy; ADP + P + Energy ⇌ ATP, PC + ADP ⇌ ATP.
- Lactic acid system: net 2 ATP; glycogen/glucose → pyruvic acid ⇌ lactic acid.
- Aerobic system: net 36 ATP per the source's classic figure; current biochemistry revises this to ~30-32 ATP (see Oxygen (Aerobic) Energy System); Krebs Cycle + Electron Transport System.
Connections
- Bioenergetics — Anaerobic vs. Aerobic Energy Production — the anaerobic/aerobic framework.
- ATP-PC (Phosphagen) System — stored-energy detail.
- Lactic Acid (Glycolytic) System — glycolytic detail (net 2 ATP).
- Oxygen (Aerobic) Energy System — oxygen-system detail (net 36 ATP).
- General Characteristics of the Energy Systems (Comparison Table) — characteristics comparison table.
Sources
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