Question

Why anaerobic respiration is less efficient than aerobic respiration.

Answer 1

Aerobic respiration:

When free or molecular oxygen participates in the respiratory breakdown of organic substrate, it is called aerobic respiration.

C₆H₁₂O₆    +     6O₂ −−−−−−−−−−−−→ 6CO₂  + 6H₂O + Energy

(686 kcal or 2870 kcal or 38 ATP)

Each glucose molecule contains 686 kcal of energy.

38 ATP x 7.3 kcal = 277.4 kcal

38 ATP x 30.6 kJ = 1162.8 kJ

Thus, in aerobic respiration of each glucose molecule, out of the 686 kcal, 277.4 kcal energy is conserved as usable form. This comes to nearly 40%.

277.4/686 x 100= 40%

As 40% energy is conserved, the efficiency of aerobic respiration is 40%.

Anaerobic respiration:

C₆H₁₂O₆   −−−−−−→ 2C₂H₅OH     +     2CO₂      +     Energy

(686 kcal)

In anaerobic respiration, 2 ATP molecules are used for breakdown.

2 ATP x 7.3 kcal = 14.6 kcal

or

2 ATP x 30.6 kJ = 61.2 kJ is conserved in anaerobic respiration of each glucose molecule.

14.6/686 x 100= 2.12%

Thus, energy efficiency of anaerobic respiration is just 2.12%.

This proves that anaerobic respiration is less efficient than aerobic respiration.