Question

How is photosynthesis different than cellular respiration?
• The process involves water.
• The process involves light.
• The process involves oxygen.
• The process involves carbon dioxide.

Answer 1

Short answer: The key difference is light. Photosynthesis requires light to convert CO2 and H2O into glucose and O2; cellular respiration does not use light and runs the reverse overall reaction.

More detail, statement by statement:
- The process involves water — Both processes involve water, but in opposite ways: photosynthesis uses (splits) H2O as a reactant in the light reactions; cellular respiration produces H2O as a product.
- The process involves light — This is a distinguishing feature: photosynthesis requires light (light-dependent reactions); cellular respiration does not.
- The process involves oxygen — Both involve O2, but oppositely: photosynthesis produces O2; aerobic cellular respiration consumes O2.
- The process involves carbon dioxide — Both involve CO2, but oppositely: photosynthesis consumes CO2 to make sugars; cellular respiration produces CO2 when breaking down sugars.