AP BIOLOGY

Detailed explanation-1: -The organic anion malate is accumulated in the central vacuole of most plant cells. Malate has several important roles in plant vacuoles, such as the maintenance of charge balance and pH regulation, as an osmolyte involved in the generation of cell turgor, and as a storage form of CO2.

Detailed explanation-2: -In a nutshell, 24-hour CAM occurs by phosphoenol pyruvate (PEP) carboxylase fixing CO(2)(HCO(3) (-)) over the night to form malic acid that is stored in plant cell vacuoles.

Detailed explanation-3: -CAM plants take up carbon dioxide at night but they cannot complete the light-mediated steps of photosynthesis. Instead they produce malic acid that is later used as a substrate to complete the C3 pathway when light is available. CAM plants, under favorable conditions, can switch to using only the C3 pathway.

Detailed explanation-4: -CAM plants have a different leaf anatomy from C3 plants, and fix the CO2 at night, when their stomata are open. CAM plants store the CO2 mostly in the form of malic acid via carboxylation of phosphoenolpyruvate to oxaloacetate, which is then reduced to malate.