Aerobic Respiration: Glycolysis

Respiration is the metabolic process by which cells release energy from organic molecules (primarily glucose) to synthesise ATP. Glycolysis is the first stage of both aerobic and anaerobic respiration. This lesson covers the location, steps, and significance of glycolysis as required by the Edexcel A-Level Biology (9BI0) specification.

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Overview of Aerobic Respiration

The overall equation for aerobic respiration is:

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy (ATP + heat)

Aerobic respiration occurs in four main stages:

Stage	Location	Key inputs	Key outputs
1. Glycolysis	Cytoplasm	Glucose, 2 ATP, 2 NAD⁺	2 pyruvate, 4 ATP (net 2), 2 reduced NAD
2. Link reaction	Mitochondrial matrix	2 pyruvate, 2 NAD⁺, 2 CoA	2 acetyl CoA, 2 CO₂, 2 reduced NAD
3. Krebs cycle	Mitochondrial matrix	2 acetyl CoA, 6 NAD⁺, 2 FAD	4 CO₂, 6 reduced NAD, 2 reduced FAD, 2 ATP
4. Oxidative phosphorylation	Inner mitochondrial membrane	Reduced NAD, reduced FAD, O₂	~34 ATP, H₂O