AP BIOLOGY

Detailed explanation-1: -In CAM photosynthesis, stomatal behaviour reverses; atmospheric CO2 is fixed at night and stomata are closed during the day. The initial CO2 fixation is performed by the enzyme phosphoenolpyruvate (PEP) carboxylase. CO2 is fixed into 4-carbon compounds, primarily malate, and stored in vacuoles as an acid.

Detailed explanation-2: -The first stable compound formed during these pathways is oxaloacetate. This compound is formed by the addition of carbon dioxide to phosphoenolpyruvate (PEP) in the presence of the enzyme phosphoenolpyruvate carboxylase.

Detailed explanation-3: -CAM plants temporally separate carbon fixation and the Calvin cycle. Carbon dioxide diffuses into leaves during the night (when stomata are open) and is fixed into oxaloacetate by PEP carboxylase, which attaches the carbon dioxide to the three-carbon molecule PEP.

Detailed explanation-4: -1. CAM photosynthesis begins at night, when the plant’s stomata open and CO2 gas is able to diffuse into the cytoplasm of CAM mesophyll cells.

Detailed explanation-5: -During the night, a plant employing CAM has its stomata open, allowing CO2 to enter and be fixed as organic acids that are stored in vacuoles. During the day the stomata are closed (thus preventing water loss), and the carbon is released to the Calvin cycle so that photosynthesis may take place.