Question

what is the main difference between c3 and c4 carbon fixation?
a. in c3 carbon fixation, plant stomata are open during the day, while they are open at night for c4 carbon fixation.
b. c3 processes take place throughout the leaf, while c4 processes take place in the inner cells.
c. c3 carbon fixation is more common in areas with high light intensity than c4 carbon fixation.
d. c3 processes are more efficient than c4 processes in high temperatures.
please select the best answer from the choices provided

Explanation:

• Option a: Incorrect. In C3 plants, stomata are open during the day. In C4 plants, stomata are also open during the day. CAM plants (a different type of photosynthetic pathway) have stomata open at night.
• Option b: Correct. In C3 carbon - fixation, the Calvin cycle (the light - independent reactions of photosynthesis) occurs throughout the mesophyll cells of the leaf. In C4 carbon - fixation, the initial carbon fixation (using PEP carboxylase) occurs in the mesophyll cells, and the Calvin cycle occurs in the bundle - sheath cells (inner cells).
• Option c: Incorrect. C4 carbon - fixation is more common in areas with high light intensity and high temperatures. C3 plants are more common in cooler and less - intense light conditions.
• Option d: Incorrect. C4 processes are more efficient than C3 processes in high temperatures because C4 plants can reduce photorespiration (a wasteful process in C3 plants under high - temperature and high - light conditions).

Answer:

B. C3 processes take place throughout the leaf, while C4 processes take place in the inner cells.