Multiple Choice
Which of the following are the main reactants required for the light-independent reactions (Calvin cycle) of photosynthesis?
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9. Photosynthesis
Light Reactions of Photosynthesis
Multiple Choice
How is ATP produced during the light reactions of photosynthesis?
A
By direct transfer of electrons to ADP
B
By the Calvin cycle enzymes
C
By chemiosmosis as protons flow through ATP synthase
D
By the breakdown of glucose
Verified step by step guidance1
Understand that ATP production during the light reactions of photosynthesis occurs in the chloroplast, specifically in the thylakoid membrane.
Recognize that light energy excites electrons in chlorophyll molecules, initiating the electron transport chain (ETC). This chain is embedded in the thylakoid membrane and drives the movement of electrons through protein complexes.
Learn that as electrons move through the ETC, energy is used to pump protons (H⁺ ions) from the stroma into the thylakoid lumen, creating a proton gradient across the thylakoid membrane. This is a key step in chemiosmosis.
Understand that the proton gradient represents potential energy. Protons flow back into the stroma through ATP synthase, a protein complex that harnesses this energy to catalyze the conversion of ADP and inorganic phosphate (Pi) into ATP. This process is known as photophosphorylation.
Note that ATP production during the light reactions is not directly related to the Calvin cycle, glucose breakdown, or direct electron transfer to ADP. It is driven by chemiosmosis and the activity of ATP synthase.
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