Actual assembly of sugars during photosynthesis—
A. Occurs during light independent reactions
B. Takes place in the stroma
C. Requires NADPH
D. Requires ATP
E. Does all of these
The correct answer and explanation is:
The correct answer is E. Does all of these.
The assembly of sugars during photosynthesis is part of the light-independent reactions, also known as the Calvin cycle. This process occurs in the stroma of the chloroplast, and it requires both NADPH and ATP. Here’s a breakdown of why all these components are necessary:
- Occurs during light-independent reactions: The light-independent reactions, or Calvin cycle, do not require light directly. Instead, they use the products of the light-dependent reactions, mainly ATP and NADPH, to convert carbon dioxide into organic molecules, such as glucose. This is where sugars are synthesized.
- Takes place in the stroma: The stroma is the fluid-filled space inside the chloroplast that surrounds the thylakoid membranes. It is in the stroma where the Calvin cycle occurs. The stroma provides the necessary enzymes and substrates required for the fixation of carbon dioxide and the formation of sugars.
- Requires NADPH: NADPH, which is generated during the light-dependent reactions, acts as a reducing agent in the Calvin cycle. It donates electrons to intermediate compounds, helping to convert carbon compounds into a higher energy state, thus facilitating the synthesis of sugars.
- Requires ATP: ATP, also produced during the light-dependent reactions, provides the energy necessary to drive the reactions in the Calvin cycle. ATP is used to phosphorylate intermediates and drive the endergonic reactions, allowing the fixation of carbon dioxide and the eventual synthesis of sugars.
In conclusion, the assembly of sugars during photosynthesis indeed requires all of these factors, making E the correct choice. The Calvin cycle depends on the products of the light-dependent reactions to convert carbon dioxide into glucose, a vital process for plant growth and energy storage.