Cellular respirationSpec 8.9
Cellular respiration is an exothermic reaction. It transfers energy to the surroundings, and some of this energy is released as heat. It happens continuously in living cells (in plants as well as animals) to release energy for metabolic processes.
Metabolic processes include building larger molecules from smaller ones, muscle contraction, and keeping the body warm in mammals and birds.
Aerobic respiration
Aerobic respiration uses oxygen to break down glucose.
glucose + oxygen → carbon dioxide + water
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O
Anaerobic respiration
Anaerobic respiration happens without oxygen. In animal cells, such as muscle cells working hard, glucose is broken down to lactic acid. In plant cells and yeast, glucose is broken down to ethanol and carbon dioxide.
glucose → lactic acid
glucose → ethanol + carbon dioxide