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
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
During the light-dependent reactions, carbon dioxide is fixed to produce sugars that form glucose.
d
The light-dependent reactions use ATP from the Calvin cycle, and the Calvin cycle uses energy from absorbed sunlight.
b
b. The light-dependent reactions take place in the thylakoid membrane, and the Calvin cycle takes place in the stroma.
The correct answer is b: The light-dependent reactions take place in the thylakoid membrane, and the Calvin cycle takes place in the stroma.
To get to this answer, let's break down each statement and analyze it:
a) The Calvin cycle converts water molecules into oxygen gas as a byproduct of its reactions.
This statement is incorrect. The Calvin cycle does not produce oxygen gas as a byproduct. Instead, the light-dependent reactions produce oxygen gas as a byproduct of splitting water molecules.
b) The light-dependent reactions take place in the thylakoid membrane, and the Calvin cycle takes place in the stroma.
This statement is correct. The light-dependent reactions occur in the thylakoid membrane, specifically in the thylakoid discs where the photosystems I and II are located. Conversely, the Calvin cycle occurs in the stroma, which is the fluid-filled space surrounding the thylakoids.
c) During the light-dependent reactions, carbon dioxide is fixed to produce sugars that form glucose.
This statement is incorrect. The light-dependent reactions do not directly fix carbon dioxide or produce glucose. Instead, they produce ATP (adenosine triphosphate) and NADPH (reduced nicotinamide adenine dinucleotide phosphate), which are then utilized in the Calvin cycle to fix carbon dioxide and produce sugars, including glucose.
d) The light-dependent reactions use ATP from the Calvin cycle, and the Calvin cycle uses energy from absorbed sunlight.
This statement is also incorrect. The light-dependent reactions do not use ATP from the Calvin cycle. Instead, they produce ATP through photophosphorylation, which is the process of converting light energy into chemical energy stored in ATP. On the other hand, the Calvin cycle uses energy from absorbed sunlight in the form of ATP and NADPH, which were produced in the light-dependent reactions.
So, the correct statement is b: The light-dependent reactions take place in the thylakoid membrane, and the Calvin cycle takes place in the stroma.