Factors Affecting Respiration

The rate of cellular respiration is influenced by several factors, including temperature, substrate availability, and oxygen concentration. This lesson also covers the practical techniques used to measure respiration rate, particularly the use of respirometers. These topics are required by the Edexcel A-Level Biology (9BI0) specification.

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Factors Affecting the Rate of Respiration

1. Temperature

Respiration is a series of enzyme-controlled reactions, so temperature affects the rate in the same way as any enzyme-catalysed process.

Temperature range	Effect on respiration rate
Below optimum	Rate increases with temperature. Molecules have more kinetic energy, so enzyme-substrate collisions occur more frequently and with more energy. The Q₁₀ value is typically around 2 (rate doubles per 10°C rise).
At optimum (~30–40°C for most organisms)	Maximum rate of respiration.
Above optimum	Rate decreases rapidly. Enzymes begin to denature — their tertiary structure unfolds, active sites change shape, and substrate binding is reduced.
Extreme temperatures (>50°C)	Enzymes are fully denatured; respiration rate drops to zero.