5.6.6 Using the Products of the Light-Dependent Reaction

Question 1

Where does the LDS take place?

Answer 1

Thylakoids

Question 2

Where does the LIS take place?

Answer 2

Stroma

Question 3

What happens during the LDS?

Answer 3

• Reduced NADP is produced when hydrogen ions combine with the carrier molecule NADP using electrons from the photolysis of water
• ATP is produced from ADP and Pi by ATP synthase in a process called photophosphorylation (ADP + Pi → ATP)
• Photophosphorylation uses the proton (H+) gradient generated by the photolysis of water
• Energy from ATP and hydrogen from reduced NADP are passed from the light-dependent stage to the light-independent stage of photosynthesis

Question 4

When are the energy and hydrogens used?

Answer 4

The energy and hydrogen are used during the light-independent reactions (known collectively as the Calvin cycle) to produce complex organic molecules, including (but not limited to) carbohydrates, such as:
- Starch (for storage)
- Sucrose (for translocation around the plant)
- Cellulose (for making cell walls)