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Multiple Choice
Which process in photosynthesis begins when carbon dioxide ($\mathrm{CO_2}$) from the atmosphere is incorporated into organic molecules?
A
Calvin cycle
B
Glycolysis
C
Photolysis
D
Electron transport chain
Verified step by step guidance
1
Understand the question: The problem is asking which process in photosynthesis incorporates carbon dioxide ($\mathrm{CO_2}$) from the atmosphere into organic molecules. This is a key step in the synthesis of sugars during photosynthesis.
Recall the main stages of photosynthesis: Photosynthesis consists of two main stages: the light-dependent reactions and the light-independent reactions (Calvin cycle). The light-dependent reactions involve capturing light energy, while the Calvin cycle focuses on carbon fixation and sugar production.
Define carbon fixation: Carbon fixation is the process of incorporating atmospheric carbon dioxide ($\mathrm{CO_2}$) into organic molecules, such as 3-phosphoglycerate (3-PGA), which occurs during the Calvin cycle.
Eliminate incorrect options: Glycolysis is a process in cellular respiration, not photosynthesis. Photolysis refers to the splitting of water molecules during the light-dependent reactions. The electron transport chain is part of the light-dependent reactions and does not involve carbon fixation.
Conclude that the Calvin cycle is the correct answer: The Calvin cycle is the stage of photosynthesis where carbon dioxide ($\mathrm{CO_2}$) is incorporated into organic molecules, making it the correct choice for this question.