AP Biology questions on C4 and CAM plants

🌿 Quick Study Guide

• ☀️ C4 and CAM plants are adaptations to hot, dry environments. They minimize photorespiration and water loss.
• 🧪 C4 plants spatially separate carbon fixation and the Calvin cycle.
• 🍃 CAM plants temporally separate these processes.
• 🧬 In C4 plants, CO₂ is initially fixed in mesophyll cells using PEP carboxylase, forming a 4-carbon compound (oxaloacetate).
• 🌍 This 4-carbon compound is then transported to bundle sheath cells, where it's decarboxylated, releasing CO₂ for the Calvin cycle.
• 🌵 CAM plants open their stomata at night, fixing CO₂ into organic acids, which are stored in vacuoles.
• 🕰️ During the day, when the stomata are closed to conserve water, the organic acids are decarboxylated, providing CO₂ for the Calvin cycle.

🤔 Practice Quiz

1. Which of the following is a primary adaptation of C4 plants to hot and dry environments?
   1. Minimizing water loss through increased transpiration.
   2. Spatially separating initial CO₂ fixation and the Calvin cycle.
   3. Temporally separating initial CO₂ fixation and the Calvin cycle.
   4. Increasing the efficiency of photorespiration.
2. In C4 plants, the initial fixation of CO₂ occurs in which type of cell?
   1. Bundle sheath cells
   2. Mesophyll cells
   3. Guard cells
   4. Epidermal cells
3. What enzyme is responsible for the initial fixation of CO₂ in C4 plants?
   1. RuBisCO
   2. PEP carboxylase
   3. ATP synthase
   4. Amylase
4. Which of the following best describes the temporal separation of steps in CAM plants?
   1. CO₂ fixation occurs in the bundle sheath cells, and the Calvin cycle occurs in the mesophyll cells.
   2. CO₂ fixation occurs during the day, and the Calvin cycle occurs at night.
   3. CO₂ fixation occurs at night, and the Calvin cycle occurs during the day.
   4. CO₂ fixation and the Calvin cycle occur simultaneously in the same cells.
5. During what time of day do CAM plants typically open their stomata?
   1. During the day
   2. At night
   3. Only during rainfall
   4. Never; they keep them closed
6. What is the primary purpose of closing stomata during the day in CAM plants?
   1. To increase CO₂ uptake
   2. To conserve water
   3. To increase the rate of photosynthesis
   4. To prevent photorespiration
7. Which of the following is an example of a CAM plant?
   1. Rice
   2. Corn
   3. Cactus
   4. Wheat