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Multiple Choice
Which is the best description of photophosphorylation?
A
The splitting of water molecules to release oxygen, protons, and electrons in the light reactions.
B
The fixation of carbon dioxide into organic molecules during the Calvin cycle.
C
The process by which light energy is used to add a phosphate group to ADP, forming ATP during photosynthesis.
D
The breakdown of glucose to produce ATP in the absence of oxygen.
Verified step by step guidance
1
Step 1: Begin by understanding the term 'photophosphorylation.' It refers to the process in photosynthesis where light energy is used to drive the addition of a phosphate group to ADP, forming ATP.
Step 2: Recognize that photophosphorylation occurs during the light-dependent reactions of photosynthesis, which take place in the thylakoid membranes of chloroplasts.
Step 3: Note that the process involves the absorption of light by chlorophyll molecules, which excites electrons and initiates the electron transport chain. This chain creates a proton gradient across the thylakoid membrane.
Step 4: Understand that the proton gradient drives ATP synthesis through the enzyme ATP synthase, which uses the energy from the flow of protons (chemiosmosis) to convert ADP and inorganic phosphate (Pi) into ATP.
Step 5: Compare photophosphorylation to other processes mentioned in the problem, such as water splitting (part of the light reactions but not photophosphorylation), carbon fixation (part of the Calvin cycle), and anaerobic glucose breakdown (a separate process called fermentation).