Study Guides/Biology/Why is Respiration Exothermic?
Study Guide · Biology

Why is Respiration Considered an Exothermic Reaction?

In Class 10 Chemistry and Biology, respiration is cited as the best example of an exothermic reaction in a living body — a reaction that releases energy.

Question (Click to Flip)

Why is respiration considered an exothermic reaction?

Answer

Respiration is exothermic because it involves the oxidation of glucose, which releases a large amount of energy in the form of ATP and heat — more energy is released than absorbed.

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Key Facts

Reaction Type: Exothermic (releases energy).

Products: CO₂ + H₂O + ATP + Heat.

Energy Released: ~2870 kJ per mole of glucose.

Body Heat: The heat released maintains body temperature.

The Reaction

During aerobic respiration, glucose is oxidized completely:

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy (ATP + Heat)

The bonds in glucose contain stored chemical energy. When oxygen breaks these bonds during oxidation, energy is released to the surroundings — not absorbed.

Why it is Exothermic

An exothermic reaction releases more energy than it absorbs. In respiration:

  • Energy needed to start the reaction: Low activation energy.
  • Energy released when glucose bonds break: 2870 kJ/mol — a huge amount.

This released energy is captured in ATP molecules (the body's energy currency) and also released as body heat (which maintains our body temperature at 37°C).

Comparison with Combustion

Burning glucose in air (combustion) also produces CO₂, water and energy — but all energy is released as heat at once. Respiration is a controlled, slow version of the same exothermic process.

Questions and Answers

Why is respiration considered an exothermic reaction?+

Respiration is exothermic because it involves the oxidation of glucose, which releases a large amount of energy in the form of ATP and heat — more energy is released than absorbed.

What is the equation for aerobic respiration?+

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy.

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