Question

In $C_{3}$ plants, the first stable product of photosynthesis during the dark reaction is

• A. malic acid
• B. oxaloacetic acid
• C. 3-phosphoglyceric acid
• D. phosphoglyceraldehyde

Answer 1

Answer: (C)

3-phosphoglyceric acid

Answer 2

In $C_{3}$ plants, the first stable product formed during dark reaction is $3$-phosphoglyceric acid. Since, it is a $3$-carbon compound hence, the pathway is referred as $C_{3}$ pathway. Oxaloacetic acid $(OAA)$ is the first stable compound in $C_{4}$ plants. It is a $4 C$ compound. This acid is converted to another $4C$ acid malic acid which enters into the chloroplast of bundle sheath cells.
In $C_{3}$ cycle, $3PGA$ is phosphorylated into $1, 3$-diphosphoglyceric acid, which is reduced into 3-phosphoglyceraldehyde.