What is the role of PEP carboxylase in C4 and CAM plants? a. It fixes CO2 into an organic acid. b. It produces ATP for the Calvin cycle. c. It replaces rubicso in the Calvin cycle. d. It releases CO2 from organic acids.

Verified step by step guidance

1. Identify the primary function of PEP carboxylase: PEP carboxylase is an enzyme that catalyzes the fixation of CO2 into a four-carbon compound, oxaloacetate, in C4 and CAM plants.
2. Understand the role of PEP carboxylase in C4 plants: In C4 plants, PEP carboxylase helps capture CO2 in mesophyll cells, forming oxaloacetate, which is then converted to malate. Malate is transported to bundle-sheath cells where CO2 is released for use in the Calvin cycle.
3. Understand the role of PEP carboxylase in CAM plants: In CAM plants, PEP carboxylase fixes CO2 into oxaloacetate during the night when stomata are open. This oxaloacetate is converted to malate and stored in vacuoles until daylight, where CO2 is released for the Calvin cycle.
4. Eliminate incorrect options based on the function of PEP carboxylase: Since PEP carboxylase is involved in CO2 fixation into organic acids, options b, c, and d can be eliminated as they do not describe this function.
5. Select the correct answer based on the role of PEP carboxylase: The correct answer is 'a. It fixes CO2 into an organic acid.' as it accurately describes the primary function of PEP carboxylase in C4 and CAM plants.

Key Concepts

PEP Carboxylase Function

PEP carboxylase is an enzyme that catalyzes the fixation of carbon dioxide (CO2) into a four-carbon compound, typically oxaloacetate, in C4 and CAM plants. This process is crucial for these plants as it allows them to efficiently capture CO2 even in low concentrations, which is essential for photosynthesis in hot and arid environments.

C4 and CAM Photosynthesis

C4 and CAM (Crassulacean Acid Metabolism) are two types of photosynthetic pathways that enable plants to minimize water loss and maximize CO2 fixation. C4 plants separate the initial CO2 fixation and the Calvin cycle spatially, while CAM plants do so temporally, fixing CO2 at night and conducting the Calvin cycle during the day, thus reducing transpiration.

Calvin Cycle

The Calvin cycle is the series of biochemical reactions that occur in the stroma of chloroplasts during photosynthesis, where CO2 is converted into glucose using ATP and NADPH produced in the light-dependent reactions. In C4 and CAM plants, the initial fixation of CO2 by PEP carboxylase is a preparatory step that enhances the efficiency of the Calvin cycle under specific environmental conditions.