2.67 Understand the origin of carbon dioxide and oxygen as waste products of metabolism and their loss from the stomata of a leaf

Both CO₂ and O₂ are waste products of metabolic reactions:

• CO₂ + H₂O > C₆H₁₂O₆ + O₂ (photosynthesis)
• C₆H₁₂O₆ + O₂>  CO₂ + H₂O (respiration)

which are carried out by plants.