Question

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

Answers

GPT-4o mini
The correct statement regarding the two main steps in photosynthesis is:

**b** 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. The Calvin cycle does not convert water molecules into oxygen gas; this occurs during the light-dependent reactions.

c. The light-dependent reactions produce ATP (and NADPH) that are then used in the Calvin cycle; the statements about energy usage are reversed.

d. During the light-dependent reactions, carbon dioxide is not fixed; carbon fixation occurs in the Calvin cycle. The light-dependent reactions primarily focus on capturing sunlight to produce energy (ATP and NADPH).

Therefore, option b is the only accurate statement.

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