12.2 Aerobic respiration
- Syllabus
- 0610–2026–2027
- Topic
- 12.2
- Level
- —
Learning objectives
12.2.1Aerobic respiration as the chemical• Describe aerobic respiration as the chemical reactions in cells that use oxygen to break down nutrient molecules to release energy12.2.2Word equation for aerobic respiration• State the word equation for aerobic respiration as: glucose + oxygen → carbon dioxide + water12.2.3Balanced chemical equation for aerobic• State the balanced chemical equation for aerobic respiration as: C 6H12O6 + 6O2 → 6CO2 + 6H2O
Describe aerobic respiration
Aerobic respiration is the set of chemical reactions in cells that uses oxygen to break down nutrient molecules and release energy.
| Part of the definition | Meaning |
|---|---|
| chemical reactions in cells | respiration is a cellular process, not simply breathing |
| uses oxygen | oxygen is a reactant |
| breaks down nutrient molecules | glucose is the required example |
| releases energy | energy is transferred for cellular and organism processes |
Energy is released by respiration; cells do not ‘make energy’, and ventilation alone is not respiration.
State the word equation for aerobic respiration
glucose + oxygen → carbon dioxide + water
| Side | Substances |
|---|---|
| reactants | glucose and oxygen are used |
| products | carbon dioxide and water are formed |
The arrow means ‘react to form’; it does not mean the equation can be reversed for respiration.
Energy is released during the reactions, but the required syllabus word equation lists the four substances shown above.
State the balanced equation for aerobic respiration
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O
| Element | Left side | Right side |
|---|---|---|
| carbon | 6 | 6 |
| hydrogen | 12 | 12 |
| oxygen | 18 | 18 |
The ratio is 1 glucose : 6 oxygen : 6 carbon dioxide : 6 water. For three glucose molecules, multiply every coefficient by three.
Balance an equation by changing coefficients in front of formulae, never by changing subscripts inside a chemical formula.