AP BIOLOGY

Detailed explanation-1: -The reason these two processes occur at the same time is that photorespiration uses oxygen while giving out carbon dioxide and the dark reaction of photosynthesis uses carbon dioxide while giving out oxygen. Thus, these processes are often studied together to understand the efficiency of the plant system.

Detailed explanation-2: -The dark reactions occur in the stroma and requires carbon dioxide and the products of light reactions (ATP and NADPH) as reactants to produce glyceraldehyde 3-phosphate, which is later used to form glucose and regenerate ribulose bisphosphate (RUBP).

Detailed explanation-3: -The dark reaction occurs outside of the thylakoids. In this reaction, the energy from ATP and NADPH are used to fix carbon dioxide (CO2). So NADH is not a product of the light reaction of photosynthesis.

Detailed explanation-4: -The Calvin cycle, which is another name for the dark reactions of photosynthesis, consists of three steps: carbon fixation, reduction, and regeneration.