Multiple Choice
Which photosynthetic pathway allows carbon dioxide to enter leaves only at night?
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9. Photosynthesis
C3, C4 & CAM Plants
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Which of the following best describes a C3 plant?
A
It uses crassulacean acid metabolism (CAM) for photosynthesis.
B
It initially fixes CO_2 into a four-carbon compound using PEP carboxylase.
C
It opens its stomata only at night to minimize water loss.
D
It fixes CO_2 directly through the Calvin cycle, producing 3-phosphoglycerate as the first stable product.
Verified step by step guidance1
Step 1: Understand the context of the question. The question is asking about the characteristics of a C3 plant, which is a type of plant that uses a specific pathway for photosynthesis. This pathway is distinct from other types like C4 and CAM pathways.
Step 2: Recall the key feature of C3 plants. C3 plants are named because the first stable product of carbon fixation in the Calvin cycle is a three-carbon compound called 3-phosphoglycerate (3-PGA). This occurs when the enzyme RuBisCO fixes CO₂ directly.
Step 3: Differentiate C3 plants from C4 and CAM plants. C4 plants initially fix CO₂ into a four-carbon compound using the enzyme PEP carboxylase, while CAM plants open their stomata at night and store CO₂ as an acid to minimize water loss. These processes are adaptations to specific environmental conditions.
Step 4: Analyze the options provided. The correct description of a C3 plant is the one that states it fixes CO₂ directly through the Calvin cycle, producing 3-phosphoglycerate as the first stable product. The other options describe characteristics of CAM or C4 plants, not C3 plants.
Step 5: Conclude that the correct answer is the option describing the direct fixation of CO₂ through the Calvin cycle, resulting in 3-phosphoglycerate as the first stable product. This is the defining feature of C3 plants.
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C3, C4 & CAM Plants practice set
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