Multiple choice

The acceptor of CO2, in CAMplants, is

  1. phosphoglyceric acid

  2. phosphoenol pyruvic acid

  3. ribulose biphosphate

  4. oxalo acetic acid
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In CAM (Crassulacean Acid Metabolism) plants, phosphoenol pyruvic acid (PEP) is the primary CO2 acceptor. During the night, PEP carboxylase fixes CO2 into oxaloacetate (which is converted to malate). During the day, malate releases CO2 for the Calvin cycle. Phosphoenol pyruvate is the 3-carbon compound that accepts CO2, not ribulose biphosphate (RuBP - used in C3 and C4 plants) or the other options listed.

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