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 primary CO2 acceptor in C4 plants is a 3-carbon molecule phosphoenol pyruvate (PEP) . The enzyme responsible for this fixation is PEP carboxylase .

Detailed explanation-3: -PEP carboxylase, which is located in the mesophyll cells, is an essential enzyme in C4 plants. In hot and dry environments, carbon dioxide concentrations inside the leaf fall when the plant closes or partially closes its stomata to reduce water loss from the leaves.

Detailed explanation-4: -Indeed, the most important biological mechanism for fixing carbon dioxide is very inefficient, which is very much down to one enzyme: ribulose‐1, 5‐bisphosphate carboxylase/oxygenase, or RuBisCo for short.

Detailed explanation-5: -Carbon Fixation in CAM Plants CAM pathway of carbon fixation or Crassulacean acid metabolism is present in plants present in arid conditions, e.g. cactus. In the CAM pathway, plants take CO2 during the night through the stomatal opening. It is converted to malic acid (4 carbon compound) and stored in vacuoles.