The two steps in photosynthesis are the light-dependent reactions and the Calvin cycle. Which of the following is true regarding these two steps? a During the light-dependent reactions, carbon dioxide is fixed to produce sugars that form glucose. b The light-dependent reactions use ATP from the Calvin cycle, and the Calvin cycle uses energy from absorbed sunlight. c The Calvin cycle converts water molecules into oxygen gas as a byproduct of its reactions. d The light-dependent reactions take place in the thylakoid membrane, and the Calvin cycle takes place in the stroma.

Answer 1

The correct statement regarding the two steps of photosynthesis is:

d) The light-dependent reactions take place in the thylakoid membrane, and the Calvin cycle takes place in the stroma.

Here’s a brief explanation of why the other options are incorrect:

• a) During the light-dependent reactions, water (not carbon dioxide) is split to produce oxygen gas as a byproduct, while the Calvin cycle is where carbon dioxide is fixed to produce sugars, including glucose.

• b) The light-dependent reactions produce ATP and NADPH, which are then used by the Calvin cycle. The statement incorrectly implies that the Calvin cycle uses ATP from the Calvin cycle itself.

• c) The Calvin cycle does not convert water into oxygen; that process occurs during the light-dependent reactions. The Calvin cycle uses carbon dioxide to produce carbohydrates.

So, option d is the accurate statement about the photosynthesis process.