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Physiology

Energy Metabolism Summary and ATP Yields

Evidence-grounded — sourced from Fysiqal's fitness knowledge graph· 1 min read
energy-systemsatpglycolysiskrebs-cyclemetabolism

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In one line

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 aerobic-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 aerobic-system); Krebs Cycle + Electron Transport System.

Connections

  • bioenergetics-overview — the anaerobic/aerobic framework.
  • atp-pc-system — stored-energy detail.
  • lactic-acid-system — glycolytic detail (net 2 ATP).
  • aerobic-system — oxygen-system detail (net 36 ATP).
  • energy-systems-comparison — characteristics comparison table.
SourceReference manual
p.340
Cited authorities in source: Fleck & Kraemer (1997).
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Educational content only — not medical advice. Always consult a qualified professional for individualized guidance, especially around injury, pregnancy, or medical conditions.

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Atlas Connections

Oxygen (Aerobic) Energy SystemClosely related
The slow-but-unlimited pathway that uses oxygen to burn carbohydrate, fat (and a little protein) for ATP — the primary fuel for endurance and the engine that restores the anaerobic systems.
ATP-PC (Phosphagen) SystemClosely related
The body's immediate, stored anaerobic energy source — ATP and phosphocreatine ready to fire instantly, fueling short, explosive efforts of roughly 0–45 seconds.
Bioenergetics — Anaerobic vs. Aerobic Energy ProductionClosely related
The umbrella concept for where muscle gets its energy — anaerobic (ATP-PC and glycolytic, no oxygen) versus aerobic (with oxygen).
General Characteristics of the Energy Systems (Comparison Table)Closely related
A side-by-side comparison of the ATP-CP, lactic acid, and oxygen systems across oxygen need, speed, fuel, capacity, endurance, and power.
Lactic Acid (Glycolytic) SystemClosely related
An anaerobic pathway that breaks glycogen/glucose down to lactic acid for a net 2 ATP, dominant in all-out efforts of about 1–3 minutes — at the cost of fatiguing acidity.