Multiple Choice
In photophosphorylation during photosynthesis, what is the role of ATP synthase in the thylakoid membrane?
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Review 4: Amino Acid Oxidation, Oxidative Phosphorylation, & Photophosphorylation
Photophosphorylation 1
Multiple Choice
During the light reactions of oxygenic photosynthesis, how is ATP primarily synthesized (photophosphorylation)?
A
By ATP synthase using the proton-motive force generated by electron transport that pumps protons into the thylakoid lumen
B
By cleavage of glucose to generate ATP through glycolysis occurring in the thylakoid lumen
C
By oxidation of NADPH coupled to phosphorylation of ADP in the stroma
D
By direct transfer of a phosphate group from a high-energy electron carrier to ADP (substrate-level phosphorylation)
Verified step by step guidance1
Understand that during the light reactions of oxygenic photosynthesis, ATP is produced through a process called photophosphorylation, which is linked to the electron transport chain in the thylakoid membrane.
Recognize that light energy excites electrons in photosystem II, which then pass through a series of carriers, driving the pumping of protons (H\(\textsuperscript{+}\)) from the stroma into the thylakoid lumen, creating a proton gradient (proton-motive force).
Know that this proton gradient represents stored energy, as there is a higher concentration of protons inside the thylakoid lumen compared to the stroma, establishing both a chemical and electrical gradient across the thylakoid membrane.
Identify that ATP synthase, an enzyme embedded in the thylakoid membrane, uses the energy released as protons flow back down their gradient into the stroma to catalyze the phosphorylation of ADP to ATP.
Conclude that ATP synthesis in this context is not by substrate-level phosphorylation or direct oxidation of NADPH, but by chemiosmotic coupling where the proton-motive force drives ATP synthase activity.
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