Question

During photosynthesis, which molecule directly provides the carbon and oxygen atoms required to build the glucose (C₆H₁₂O₆) molecule?

 1) NADPH

 2) oxygen (O2)

 3) water (H2O)

 4) carbon dioxide (CO2)

 5) ATP

Answer 1

4) Carbon dioxide (CO2)

During photosynthesis, CO2 directly provides the carbon and oxygen atoms required to build the glucose molecule. It is in the process of photosynthesis that the cells use not only carbon dioxide but also energy from the sunlight to make sugar molecule in the form of glucose and oxygen as its biproducts. Here the carbon dioxide and water are the main reactants of the photosynthesis other than sunlight which provides energy in the photolysis of water molecules. So, the carbon and oxygen in the produced glucose molecule is from the carbon dioxide only.