Aerobic respiration and key symbols
Bioenergetics • Respiration
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Key concepts
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Definition of aerobic respiration
Aerobic respiration is a series of controlled chemical reactions that release energy from glucose in the presence of oxygen. The process requires oxygen and produces carbon dioxide and water as products, with energy released for cellular use. The organelle where most aerobic respiration occurs is the mitochondrion .
Word equation and balanced symbol equation
The word equation for aerobic respiration states that glucose + oxygen → carbon dioxide + water. The fully balanced symbol equation represents the same reaction with chemical formulas: C6H12O6 + 6O2 → 6CO2 + 6H2O. The balanced symbol equation shows the relative number of molecules involved in the reaction and helps track atoms through the process .
Reactants and products
Reactants in aerobic respiration are glucose (the fuel) and oxygen (the oxidising gas). The products are carbon dioxide and water. Energy is released during the reaction because chemical bonds in glucose and oxygen rearrange to form products with lower overall chemical energy, so energy leaves the system (exothermic) .
Key chemical symbols to recognise
Glucose is represented by the molecular formula C6H12O6. Oxygen as a molecule is O2. Carbon dioxide is CO2. Water is H2O. Recognition of these symbols allows conversion between word and symbol equations and enables balancing of the chemical equation for respiration .
Limiting factors and practical constraints
Oxygen availability limits the rate of aerobic respiration: lower oxygen concentration reduces reaction rate because oxygen is a reactant. Glucose supply also limits rate because fewer fuel molecules reduce energy release. Gas exchange and diffusion across exchange surfaces or transport by the blood affect oxygen and glucose delivery; smaller or less efficient exchange surfaces reduce supply and therefore lower respiration rate .
Key notes
Important points to keep in mind