Rubisco is __________.

• A. the enzyme responsible for splitting H₂O to produce O₂ in photosynthesis
• B. the enzyme that forms a four-carbon compound in CAM photosynthesis
• C. the first stable intermediate in C₄ photosynthesis
• D. the five-carbon sugar molecule that reacts with CO₂ to begin the Calvin cycle
• E. the enzyme in plants that captures CO₂ to begin the Calvin cycle

Answer: (E)

Verified step by step guidance

1. Understand the role of Rubisco in photosynthesis: Rubisco is an enzyme that plays a crucial role in the Calvin cycle, which is part of the photosynthesis process in plants.
2. Identify the function of Rubisco: It catalyzes the reaction between carbon dioxide (CO2) and ribulose-1,5-bisphosphate (RuBP), a five-carbon sugar, to form two molecules of 3-phosphoglycerate.
3. Clarify the Calvin cycle: The Calvin cycle is a series of biochemical reactions that occur in the stroma of chloroplasts in photosynthetic organisms. It is responsible for converting CO2 and other compounds into glucose.
4. Differentiate Rubisco from other enzymes: Rubisco is not involved in splitting water (H2O) to produce oxygen (O2), nor is it responsible for forming four-carbon compounds in CAM or C4 photosynthesis.
5. Conclude with the correct role of Rubisco: Rubisco is the enzyme in plants that captures CO2 to begin the Calvin cycle, making it essential for carbon fixation in photosynthesis.